Document:

EXECUTION COPY

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              CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                                   (Depositor)

                                       and

                             COLUMN FINANCIAL, INC.
                                    (Seller)

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                        MORTGAGE LOAN PURCHASE AGREEMENT

                           Dated as of August 1, 2001

                   -------------------------------------------

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                                TABLE OF CONTENTS

                                                                            Page

Section 1.    Transactions on or Prior to the Closing Date..................
Section 2.    Closing Date Actions..........................................
Section 3.    Conveyance of Mortgage Loans..................................
Section 4.    Depositor's Conditions to Closing.............................
Section 5.    Seller's Conditions to Closing................................
Section 6.    Representations and Warranties of Seller......................
Section 7.    Obligations of Seller.........................................
Section 8.    Crossed Loans.................................................
Section 9.    Rating Agency Fees; Costs and Expenses Associated with a
               Defeasance...................................................
Section 10.   Representations and Warranties of Depositor...................
Section 11.   Survival of Certain Representations, Warranties and
               Covenants....................................................
Section 12.   [Reserved]....................................................
Section 13.   Expenses; Recording Costs.....................................
Section 14.   Notices.......................................................
Section 15.   Examination of Mortgage Files.................................
Section 16.   Successors....................................................
Section 17.   Governing Law.................................................
Section 18.   Severability..................................................
Section 19.   Further Assurances............................................
Section 20.   Counterparts..................................................
Section 21.   Treatment as Security Agreement...............................
Section 22.   Recordation of Agreement......................................

Schedule I    Schedule of Transaction Terms
Schedule II-A Mortgage Loan for Column Loans
Schedule II-B Mortgage Loan Schedule for PNC Loans
Schedule III  Mortgage Loans Constituting Mortgage Groups
Schedule IV   Mortgage Loans with Lost Mortgage Notes
Schedule V    Exceptions with Respect to Seller's Representations and Warranties

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Exhibit A   Representations and Warranties of Seller Regarding the Mortgage
            Loans
Exhibit B   Form of Lost Mortgage Note Affidavit
Exhibit C   Form of Assignment of Mortgage(s) and Assignment of Assignment of
            Lessor's Interests in Leases, Rents and Profits

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                        MORTGAGE LOAN PURCHASE AGREEMENT

            This Mortgage Loan Purchase Agreement (this "Agreement"), dated as
of August 1, 2001, is made by and between COLUMN FINANCIAL, INC., a Delaware
corporation ("Seller"), and CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES
CORP., a Delaware corporation (the "Depositor").

                                    RECITALS

            I. Capitalized terms used herein without definition have the
meanings ascribed to them in the Schedule of Transaction Terms attached hereto
as Schedule I, which is incorporated herein by this reference, or, if not
defined therein, in the Pooling and Servicing Agreement.

            II. On the Closing Date, and on the terms set forth herein, Seller
has agreed to sell to Depositor and Depositor has agreed to purchase from Seller
the Mortgage Loans identified on the schedules (collectively, the "Mortgage Loan
Schedule") annexed hereto as Schedule II-A and Schedule II-B. Depositor intends
to deposit the Mortgage Loans and other assets into the Trust Fund created
pursuant to the Pooling and Servicing Agreement and to cause the issuance of the
Certificates.

                                    AGREEMENT

            NOW, THEREFORE, on the terms and conditions set forth below and for
good and valuable consideration, the receipt and adequacy of which is hereby
acknowledged, Depositor and Seller agree as follows:

            Section 1. Transactions on or Prior to the Closing Date. On or prior
to the Closing Date, Seller shall have delivered the Mortgage Files with respect
to each of the Mortgage Loans listed in Schedule II-A to Wells Fargo Bank
Minnesota, N.A. as trustee (the "Trustee"), against receipt by Seller of a trust
receipt, pursuant to an arrangement between Seller and the Trustee; provided,
however, that item (p) in the definition of Mortgage File (below) shall be
delivered to the Servicer for inclusion in the Servicer File (defined below)
with a copy delivered to the Trustee for inclusion in the Mortgage File.

            Section 2. Closing Date Actions. The sale of the Mortgage Loans
shall take place on the Closing Date, subject to and simultaneously with the
deposit of the Mortgage Loans into the Trust Fund, the issuance of the
Certificates and the sale of (a) the Offered Certificates by Depositor to the
Underwriters pursuant to the Underwriting Agreement and (b) the Private
Certificates by Depositor to the Initial Purchaser pursuant to the Certificate
Purchase Agreement. The closing shall take place at the offices of Cadwalader,
Wickersham & Taft, 100 Maiden Lane, New York, New York 10038, or such other
location as agreed upon between the parties hereto. On the Closing Date, the
following actions shall take place in sequential order on the terms set forth
herein:

            (i) Seller shall sell to Depositor, and Depositor shall purchase
      from Seller, the Mortgage Loans pursuant to this Agreement for the
      Mortgage Loan Purchase Price payable in accordance with instructions
      previously provided to Depositor by Seller. The Mortgage Loan Purchase
      Price (as defined herein) shall be paid by Depositor to Seller or at its
      direction by wire transfer in immediately available funds to an account
      designated by Seller on or prior to the Closing Date. The "Mortgage Loan
      Purchase Price" paid by Depositor shall be equal to $925,867,935. In
      addition, for no consideration other than the Mortgage Loan Purchase
      Price, the Seller shall acquire, or cause a nominee to acquire, Seller's
      proportionate share of the residual Certificates under the Pooling and
      Servicing Agreement. (ii) Pursuant to the terms of the Pooling and
      Servicing Agreement, Depositor shall sell all of its right, title and
      interest in and to the Mortgage Loans to the Trustee for the benefit of
      the Holders of the Certificates.

            (iii) Depositor shall sell to the Underwriters, and the Underwriters
      shall purchase from Depositor, the Offered Certificates pursuant to the
      Underwriting Agreement, and Depositor shall sell to the Initial Purchaser,
      and the Initial Purchaser shall purchase from Depositor, the Private
      Certificates pursuant to the Certificate Purchase Agreement.

            (iv) The Underwriters will offer the Offered Certificates for sale
      to the public pursuant to the Prospectus and the Prospectus Supplement and
      the Initial Purchaser will privately place certain classes of the
      Certificates pursuant to the Offering Circular.

            Section 3. Conveyance of Mortgage Loans. On the Closing Date, Seller
shall sell, convey, assign and transfer, subject to that certain Servicing
Rights Purchase Agreement, dated as of August 28, 2001, between the Seller and
Midland Loan Services, Inc., without recourse except as provided herein, to
Depositor, free and clear of any liens, claims or other encumbrances, all of
Seller's right, title and interest in, to and under: (i) each of the Mortgage
Loans identified on the Mortgage Loan Schedule; (ii) the Owner Trust Certificate
Purchase Agreement; and (iii) all property of Seller described in Section 21(b)
this Agreement, including, without limitation, (A) all scheduled payments of
interest and principal due on or with respect to the Mortgage Loans after the
Cut-off Date and (B) all other payments of interest, principal or prepayment
premiums received on or with respect to the Mortgage Loans after the Cut-off
Date, other than any such payments of interest or principal or prepayment
premiums that were due on or prior to the Cut-off Date. Each Mortgage File shall
contain the following documents:

            (a) the original Note, or with respect to those Mortgage Loans
listed in Schedule IV hereto, a "lost note affidavit" substantially in the form
of Exhibit B hereto and a true and complete copy of the Note, bearing, or
accompanied by, all prior and intervening endorsements or assignments showing a
complete chain of endorsement or assignment from the Mortgage Loan Originator
either in blank or to the Seller, and further endorsed (at the direction of the
Depositor given pursuant to the Mortgage Loan Purchase Agreement) by the Seller,
on its face or by allonge attached thereto, without recourse, to the order of
the Trustee in the following form: "Pay to the order of Wells Fargo Bank
Minnesota, N.A., as trustee for the registered Holders of Credit Suisse First
Boston Mortgage Securities Corp., Commercial Mortgage Pass-Through Certificates,
Series 2001-CP4, without recourse, representation or warranty, express or
implied;"

            (b) a duplicate original Mortgage or a counterpart thereof or, if
such Mortgage has been returned by the related recording office, (A) an
original, (B) a certified copy or (C) a copy thereof from the applicable
recording office and originals or counterparts (or originals or copies of
certified copies from the applicable recording office) of any assignments
thereof showing a complete chain of assignment from the Mortgage Loan Originator
to the Seller, in each case in the form submitted for recording or, if recorded,
with evidence of recording indicated thereon;

            (c) an original Assignment of Mortgage substantially in the form of
Exhibit C hereto, in recordable form, either in blank or from the Seller to
"Wells Fargo Bank Minnesota, N.A., as trustee for the registered Holders of
Credit Suisse First Boston Mortgage Securities Corp., Commercial Mortgage
Pass-Through Certificates, Series 2001-CP4;"

            (d) an original, counterpart or copy of any related Assignment of
Leases (if such item is a document separate from the Mortgage) and the
originals, counterparts or copies of any assignments thereof showing a complete
chain of assignment from the Mortgage Loan Originator of the Loan to the Seller,
in each case in the form submitted for recording or, if recorded, with evidence
of recording thereon;

            (e) an original assignment of any related Assignment of Leases (if
such item is a document separate from the Mortgage), substantially in the form
of Exhibit C hereto in recordable form, either in blank or from the Seller to
"Wells Fargo Bank Minnesota, N.A., as trustee for the registered Holders of
Credit Suisse First Boston Mortgage Securities Corp., Commercial Mortgage
Pass-Through Certificates, Series 2001-CP4;"

            (f) an original or true and complete copy of any related Security
Agreement (if such item is a document separate from the Mortgage) and the
originals or copies of any assignments thereof showing a complete chain of
assignment from the Mortgage Loan Originator to the Seller;

            (g) an original assignment of any related Security Agreement (if
such item is a document separate from the Mortgage), either in blank or from the
Seller (or the Mortgage Loan Originator) to "Wells Fargo Bank Minnesota, N.A.,
as trustee for the registered Holders of Credit Suisse First Boston Mortgage
Securities Corp., Commercial Mortgage Pass-Through Certificates, Series
2001-CP4," which assignment may be included as part of an omnibus assignment
covering other documents relating to the Mortgage Loan provided that such
omnibus assignment is effective under applicable law;

            (h) originals or copies of all (A) assumption agreements, (B)
modifications, (C) written assurance agreements and (D) substitution agreements,
together with any evidence of recording thereon or in the form submitted for
recording, in those instances where the terms or provisions of the Mortgage,
Note or any related security document have been modified or the Mortgage Loan
has been assumed;

            (i) the original lender's title insurance policy or a copy thereof
(together with all endorsements or riders that were issued with or subsequent to
the issuance of such policy), or if the policy has not yet been issued, a
binding written commitment (which may be a pro forma or specimen title insurance
policy which has been accepted or approved in writing by the related title
insurance company) or interim binder that is marked as binding and countersigned
by the title company, insuring the priority of the Mortgage as a first lien on
the related Mortgaged Property, relating to such Mortgage Loan;

            (j) the original or a counterpart of any guaranty of the obligations
of the Borrower under the Mortgage Loan;

            (k) certified or other copies of all UCC Financing Statements and
continuation statements which show the filing or recording thereof or copies
thereof in the form submitted for filing or recording sufficient to perfect (and
maintain the perfection of) the security interest held by the Mortgage Loan
Originator (and each assignee prior to the Trustee) in and to the personalty of
the Borrower at the Mortgaged Property, and original UCC assignments in a form
suitable for filing or recording, sufficient to transfer such security interest
to the Trustee;

            (l) the original or copy of the power of attorney (with evidence of
recording thereon) granted by the Borrower if the Mortgage, Note or other
document or instrument referred to above was not signed by the Borrower;

            (m) with respect to any debt of a Borrower permitted under the
related Mortgage Loan, an original or copy of a subordination agreement,
standstill agreement or other intercreditor agreement relating to such other
debt, if any, including any mezzanine loan documents or preferred equity
documents;

            (n) if any related Lock-Box Agreement or Cash Collateral Agreement
is separate from the Mortgage or Loan Agreement, a copy thereof; with respect to
the Cash Collateral Accounts and Lock-Box Accounts, if any, a copy of the UCC-1
financing statements, if any, submitted for filing with respect to the Seller's
security interest in the Cash Collateral Accounts and Lock-Box Accounts and all
funds contained therein (and UCC-2 or UCC-3 financing statement assignments
assigning such security interest to the Trustee on behalf of the
Certificateholders);

            (o) an original or counterpart of the Loan Agreement (if separate
from the Mortgage);

            (p) the originals of letters of credit, if any, relating to the
Mortgage Loans, and amendments thereto which entitles the Trust to draw thereon;

            (q) the original environmental indemnity agreement, if any, related
to the Mortgage Loan;

            (r) any related environmental insurance policies;

            (s) the original ground lease, if any, or a certified copy thereof;
and

            (t) any additional documents required to be added to the Mortgage
File pursuant to the Pooling and Servicing Agreement.

            Notwithstanding the foregoing, in the event that, in connection with
any Mortgage Loan listed on Schedule II-A hereto, the Seller cannot deliver, or
cause to be delivered, an original, counterpart or certified copy of any of the
documents required to be delivered pursuant to clauses (b), (d), (h), (k) (with
respect to UCC financing statements and assignments recorded or filed other than
in accordance with the transfer contemplated by this Agreement), (l) and (n)
above with evidence of recording or filing thereon on the Closing Date, solely
because of a delay caused by the public recording or filing office where such
document or instrument has been delivered for recordation or filing, the Seller
shall deliver, or cause to be delivered, to the Trustee a duplicate original or
true copy of such document certified by the applicable public recording or
filing office, the applicable title insurance company or the Seller to be a true
and complete duplicate original or copy of the original thereof submitted for
recording or filing.

            Notwithstanding the foregoing, in the event that, in connection with
any Mortgage Loan listed on Schedule II-A hereto, the Seller cannot deliver, or
cause to be delivered, an original, counterpart or certified copy of any of the
documents required to be delivered pursuant to clauses (b), (d), (h), (k) (with
respect to UCC financing statements and assignments recorded or filed other than
in accordance with the transfer contemplated by this Agreement), (l) and (n)
above with evidence of recording or filing thereon, for any other reason,
including without limitation, that such non-delivered document has been lost,
the delivery requirements of this Agreement shall be deemed to have been
satisfied and such non-delivered document shall be deemed to have been included
in the related Mortgage File if a photocopy of such non-delivered document (with
evidence of recording or filing thereon and certified by the appropriate
recording or filing office to be a true and complete copy of the original
thereof as filed or recorded) is delivered to the Trustee on or before the
Closing Date.

            Notwithstanding the foregoing, in the event that the Seller cannot
deliver to the Trustee any UCC-2 or UCC-3 assignment with the filing information
of the UCC-1 financing statement with respect to any Mortgage Loan listed on
Schedule II-A hereto being assigned, solely because such UCC-1 financing
statement has not been returned by the public filing office where such UCC-1
financing statement has been delivered for filing, Seller shall deliver or cause
to be delivered to the Trustee a photocopy of such UCC-2 or UCC-3 assignment
with the filing information left blank. The Seller, promptly upon receipt of the
applicable filing information of the UCC-1 financing statement being so
assigned, shall deliver or cause to be delivered to the Trustee the original
UCC-2 or UCC-3 assignment with all appropriate filing information set forth
thereon.

            Within ten (10) Business Days of the Closing Date, the Seller shall
deliver the Servicer Files with respect to each of the Mortgage Loans listed on
Schedule II-A hereto to the Servicer under the Pooling and Servicing Agreement
on behalf of the Trustee in trust for the benefit of the Certificateholders.
Each such Servicer File shall contain all documents and records in the Seller's
possession relating to such applicable Mortgage Loans (including reserve and
escrow agreements, cash management agreements, lockbox agreements, financial
statements and any other information provided by the respective Borrower from
time to time, but excluding documents prepared by the Seller or any of its
Affiliates solely for internal communication) that are not required to be a part
of a Mortgage File in accordance with the definition thereof, together with
copies of all instruments and documents which are required to be a part of the
related Mortgage File in accordance with the definition thereof.

            For purposes of this Section 3, and notwithstanding any contrary
provision hereof or of the definition of "Mortgage File", if there exists with
respect to any group of Crossed Loans only one original or certified copy of any
document or instrument described in the definition of "Mortgage File" which
pertains to all of the Crossed Loans in such group of Crossed Loans, the
inclusion of the original or certified copy of such document or instrument in
the Mortgage File for any of such Crossed Loans and the inclusion of a copy of
such original or certified copy in each of the Mortgage Files for the other
Crossed Loans in such group of Crossed Loans, shall be deemed the inclusion of
such original or certified copy, as the case may be, in the Mortgage File for
each such Crossed Loan.

            The Trustee, as assignee or transferee of Depositor, shall be
entitled to all scheduled principal payments due after the Cut-off Date, all
other payments of principal due and collected after the Cut-off Date, and all
payments of interest on the Mortgage Loans, minus that portion of any such
payment which is allocable to the period on or prior to the Cut-off Date. All
scheduled payments of principal due on or before the Cut-off Date and collected
after the Cut-off Date, together with the accompanying interest payments, shall
belong to Seller.

            Upon the sale of the Mortgage Loans from Seller to Depositor
pursuant hereto, the ownership of each Mortgage Note, the Mortgage and the
contents of the related Mortgage File shall be vested in Depositor and the
ownership of all records and documents with respect to the related Mortgage Loan
prepared by or which come into the possession of Seller as seller of the
Mortgage Loans hereunder, exclusive in each case of documents prepared by Seller
or any of its affiliates solely for internal uses, shall immediately vest in
Depositor. All Monthly Payments, Principal Prepayments and other amounts
received by Seller and not otherwise belonging to Seller pursuant to this
Agreement shall be sent by Seller within three (3) Business Days of Seller's
receipt thereof to the Servicer via wire transfer for deposit by the Servicer
into the Collection Account.

            In connection with the Seller's assignment pursuant to this section,
the Seller shall deliver, and hereby represents and warrants that it has
delivered, to the Depositor, on or before the Closing Date, a fully executed
original counterpart of each of the Owner Trust Certificate Purchase Agreement,
as in full force and effect, without amendment or modification, on the Closing
Date.

            Section 4. Depositor's Conditions to Closing. The obligations of
Depositor to purchase the Mortgage Loans and pay the Mortgage Loan Purchase
Price at the Closing Date under the terms of this Agreement are subject to the
satisfaction of each of the following conditions at or before the Closing:

            (a) Each of the obligations of the Seller required to be performed
by it on or prior to the Closing Date pursuant to the terms of this Agreement
shall have been duly performed and complied with in all material respects; all
of the representations and warranties of Seller under this Agreement shall be
true and correct in all material respects as of the Closing Date; and no event
shall have occurred with respect to the Seller or any of the Mortgage Loans and
related Mortgage Files which, with notice or the passage of time, would
constitute a material default under this Agreement; and Depositor shall have
received certificates to the foregoing effect signed by authorized officers of
Seller.

            (b) Depositor, or if directed by Depositor, the Trustee or the
Depositor's attorneys, shall have received in escrow, all of the following
closing documents, in such forms as are agreed upon and reasonably acceptable to
the Depositor and the Seller, duly executed by all signatories other than
Depositor, as required pursuant to the respective terms thereof:

            (i) the Mortgage Files, which shall have been delivered to and held
      by the Trustee on behalf of Seller;

            (ii) the Mortgage Loan Schedule;

            (iii) the certificate of the Seller confirming its representations
      and warranties set forth in Section 6 as of the Closing Date;

            (iv) an opinion or opinions of Seller's counsel, dated the Closing
      Date, in form acceptable to the Depositor as to various corporate matters
      and such other matters as shall be reasonably required by the Depositor.

            Such opinion may express its reliance as to factual matters on,
among other things specified in such opinion, the representations and warranties
made herein, and on certificates or other documents furnished by officers of
Seller.

            In rendering the opinions expressed above, such counsel may limit
such opinions to matters governed by the General Corporation Law of the State of
Delaware and the laws of the State of New York and the United States and shall
not be required to express any opinion with respect to the registration or
qualification of the Certificates under any applicable state or federal
securities laws.

            Such counsel shall state that, although such counsel has not
specifically considered the possible applicability to Seller of any other laws,
regulations, judgments, orders or decrees, no facts have been disclosed to such
counsel that cause such counsel to conclude that any other consent, approval or
action is required;

            (v) such other certificates of Seller's officers or others and such
      other documents to evidence fulfillment of the conditions set forth in
      this Agreement as Depositor or its counsel may reasonably request.

            (vi) all other information, documents, certificates, or letters with
      respect to the Mortgage Loans or the Sellers and their Affiliates as are
      reasonably requested by the Depositor in order for the Depositor to
      perform any of it obligations or satisfy any of the conditions on its part
      to be performed or satisfied pursuant to any sale of Mortgage Loans by the
      Depositor as contemplated herein;

            (c) The Seller shall have performed or complied with all other terms
and conditions of this Agreement which it is required to perform or comply with
at or before the Closing and shall have the ability to perform or comply with
all duties, obligations, provisions and terms which it is required to perform or
comply with after the Closing.

            (d) The Seller shall have delivered to the Trustee, on or before the
Closing Date, five limited powers of attorney in favor of the Trustee and
Special Servicer empowering the Trustee and, in the event of the failure or
incapacity of the Trustee, the Special Servicer, to record, at the expense of
the Seller, any Mortgage Loan Documents required to be recorded and any
intervening assignments with evidence of recording thereon that are required to
be included in the Mortgage Files. The Seller shall reasonably cooperate with
the Trustee and the Special Servicer in connection with any additional powers or
revisions thereto that are requested by such parties.

            Section 5. Seller's Conditions to Closing. The obligations of Seller
under this Agreement shall be subject to the satisfaction, on the Closing Date,
of the following conditions:

            (a) Each of the obligations of Depositor required to be performed by
it on or prior to the Closing Date pursuant to the terms of this Agreement shall
have been duly performed and complied with in all material respects; and all of
the representations and warranties of Depositor under this Agreement shall be
true and correct in all material respects as of the Closing Date; and no event
shall have occurred with respect to Depositor which, with notice or the passage
of time, would constitute a material default under this Agreement, and Seller
shall have received certificates to that effect signed by authorized officers of
Depositor.

            (b) Seller shall have received all of the following closing
documents, in such forms as are agreed upon and reasonably acceptable to Seller
and Depositor, duly executed by all signatories other than Seller, as required
pursuant to the respective terms thereof:

                  (A) an officer's certificate of Depositor, dated as of the
            Closing Date, with the resolutions of Depositor authorizing the
            transactions set forth therein, together with copies of the charter,
            by-laws and certificate of good standing dated as of a recent date
            of Depositor;

                  (B) such other certificates of its officers or others, such
            opinions of Depositor's counsel and such other documents required to
            evidence fulfillment of the conditions set forth in this Agreement
            as Seller or its counsel may reasonably request; and

            (c) The Depositor shall have performed or complied with all other
terms and conditions of this Agreement which it is required to perform or comply
with at or before the Closing and shall have the ability to perform or comply
with all duties, obligations, provisions and terms which it is required to
perform or comply with after Closing.

            Section 6. Representations and Warranties of Seller.

            (a) Seller represents and warrants to Depositor as of the date
hereof, as follows:

            (i) Seller is duly organized and is validly existing as a
      corporation in good standing under the laws of Delaware. Seller has
      conducted and is conducting its business so as to comply in all material
      respects with all applicable statutes and regulations of regulatory bodies
      or agencies having jurisdiction over it, except where the failure so to
      comply would not have a materially adverse effect on the performance by
      Seller of this Agreement, and there is no charge, investigation, action,
      suit or proceeding before or by any court, regulatory authority or
      governmental agency or body pending or, to the knowledge of Seller,
      threatened, which is reasonably likely to materially and adversely affect
      the performance by Seller of this Agreement or the consummation of
      transactions contemplated by this Agreement.

            (ii) Seller has the full power, authority and legal right to hold,
      transfer and covey the Mortgage Loans owned by it and to execute and
      deliver this Agreement (and all agreements and documents executed and
      delivered by Seller in connection herewith) and to perform all
      transactions of Seller contemplated by this Agreement (and all agreements
      and documents executed and delivered by Seller in connection herewith).
      Seller has duly authorized the execution, delivery and performance of this
      Agreement (and all agreements and documents executed and delivered by
      Seller in connection herewith), and has duly executed and delivered this
      Agreement (and all agreements and documents executed and delivered by
      Seller in connection herewith). This Agreement (and each agreement and
      document executed and delivered by Seller in connection herewith),
      assuming due authorization, execution and delivery thereof by each other
      party thereto, constitutes the legal, valid and binding obligation of
      Seller enforceable in accordance with its terms, except as such
      enforcement may be limited by bankruptcy, insolvency, reorganization,
      receivership, moratorium or other laws relating to or affecting the rights
      of creditors generally, by general principles of equity (regardless of
      whether such enforcement is considered in a proceeding in equity or at
      law) and by considerations of public policy.

            (iii) Neither the execution and delivery of this Agreement, nor the
      fulfillment of or compliance with the terms and conditions of this
      Agreement by Seller, will (a) conflict with or result in a breach of any
      of the terms, conditions or provisions of Seller's certificate of
      incorporation, as amended, or other organizational documents; (b) conflict
      with, result in a breach of, or constitute a default or result in an
      acceleration under, any agreement or instrument to which Seller is now a
      party or by which it (or any of its properties) is bound if compliance
      therewith is necessary (1) to ensure the enforceability of this Agreement
      or (2) for Seller to perform its duties and obligations under this
      Agreement (or any agreement or document executed and delivered by Seller
      in connection herewith); (c) conflict with or result in a breach of any
      legal restriction if compliance therewith is necessary (1) to ensure the
      enforceability of this Agreement or (2) for Seller to perform its duties
      and obligations under this Agreement (or any agreement or document
      executed and delivered by Seller in connection herewith); (d) result in
      the violation of any law, rule, regulation, order, judgment or decree to
      which Seller or its property is subject if compliance therewith is
      necessary (1) to ensure the enforceability of this Agreement or (2) for
      Seller to perform its duties and obligations under this Agreement (or any
      agreement or document executed and delivered by Seller in connection
      herewith); or (e) result in the creation or imposition of any lien, charge
      or encumbrance that would have a material adverse effect upon Seller's
      ability to perform its duties and obligations under this Agreement (or any
      agreement or document executed and delivered by Seller in connection
      herewith), or materially impair the ability of the Depositor to realize on
      the Mortgage Loans owned by Seller.

            (iv) Seller is solvent and the sale of Mortgage Loans (1) will not
      cause Seller to become insolvent and (2) is not intended by Seller to
      hinder, delay or defraud any of its creditors.

            (v) No consent, approval, authorization or order of, or registration
      or filing with, or notice to, any court or governmental agency or body
      having jurisdiction or regulatory authority over Seller is required for
      (a) Seller's execution and delivery of this Agreement (and each agreement
      and document executed and delivered by Seller in connection herewith), (b)
      Seller's transfer and assignment of the Mortgage Loans owned by it, or (c)
      the consummation by Seller of the transactions contemplated by this
      Agreement (and each agreement and document executed and delivered by
      Seller in connection herewith) or, to the extent so required, such
      consent, approval, authorization, order, registration, filing or notice
      has been obtained, made or given (as applicable), except that Seller may
      not be duly qualified to transact business as a foreign corporation or
      licensed in one or more states if such qualification or licensing is not
      necessary to ensure the enforceability of this Agreement (or any agreement
      or document executed and delivered by Seller in connection herewith).

            (vi) The consideration received by Seller upon the sale of the
      Mortgage Loans owned by it constitutes fair consideration and reasonably
      equivalent value for such Mortgage Loans.

            (vii) Seller does not believe, nor does it have any reason or cause
      to believe, that it cannot perform each and every covenant of Seller
      contained in this Agreement (or any agreement or document executed and
      delivered by Seller in connection herewith).

            (viii) There are no actions, suits proceedings pending or to
      Seller's knowledge threatened in writing against Seller which are
      reasonably likely to draw into question the validity of this Agreement (or
      any agreement or document executed and delivered by Seller in connection
      herewith) or which, either in any one instance or in the aggregate, are
      reasonably likely to materially impair the ability of Seller to perform
      its duties and obligations under this Agreement (or any agreement or
      document executed and delivered by Seller in connection herewith).

            (ix) Seller's performance of its duties and obligations under this
      Agreement (and each agreement or document executed and delivered by Seller
      in connection herewith) is in the ordinary course of business of Seller
      and Seller's transfer, assignment and conveyance of the Mortgage Loans
      owned by it pursuant to this Agreement are not subject to the bulk
      transfer or an similar statutory provisions in effect in any applicable
      jurisdiction.

            (x) Seller has not dealt with any Person that may be entitled, by
      reason of any act or omission of Seller, to any commission or compensation
      in connection with the sale of the Mortgage Loans owned by it to the
      Depositor hereunder except for the reimbursement of expenses as described
      herein or otherwise in connection with the transactions described in
      Section 2 and the commissions or compensation owed to the Underwriters or
      the Initial Purchasers.

            (xi) Seller is not in default or breach of any agreement or
      instrument to which Seller is now a party or by which it (or any of its
      properties) is bound which breach or default would materially and
      adversely affect the ability of Seller to perform its obligations under
      this Agreement.

            (xii) Except as set forth on Schedule V hereto, the representations
      and warranties contained in Exhibit A hereto are true and correct in all
      material respects as of the date hereof with respect to the Mortgage Loans
      identified on Schedule II-A.

            Section 7. Obligations of Seller. Each of the representations and
warranties contained in or required to be made by Seller pursuant to Section 6
of this Agreement shall survive the sale of the Mortgage Loans and shall
continue in full force and effect, notwithstanding any restrictive or qualified
endorsement on the Notes and notwithstanding subsequent termination of this
Agreement or the Pooling and Servicing Agreement. The representations and
warranties contained in or required to be made by Seller pursuant to Section 6
of this Agreement shall not be impaired by any review or examination of the
Mortgage Files or other documents evidencing or relating to the Mortgage Loans
or any failure on the part of Depositor to review or examine such documents and
shall inure to the benefit of any initial transferee of the Mortgage Loans from
Depositor including, without limitation, the Trustee for the benefit of the
Holders of the Certificates, notwithstanding (1) any restrictive or qualified
endorsement on any Note, Assignment of Mortgage or reassignment of Assignment of
Leases or (2) any termination of this Agreement prior to the Closing.

            If any Certificateholder, the Servicer, the Special Servicer or the
Trustee discovers or receives notice: of a breach of any of the representations
or warranties made by the Seller with respect to the Mortgage Loans listed on
Schedule II-A hereto, as of the date hereof in Section 6(a)(xii) or as of the
Closing Date pursuant to Section 4(b)(iii) (a "Breach"); or that (a) any
document required to be included in the Mortgage File related to any Mortgage
Loan listed on Schedule II-A hereto is not in the Trustee's possession within
the time period required herein or (b) such document has not been properly
executed or is otherwise defective on its face (each, a "Defect" in the related
Mortgage File), such party shall give notice to the Servicer, the Special
Servicer, the Trustee and the Rating Agencies. If the Servicer or the Special
Servicer determines that such Breach or Defect materially and adversely affects
the value of any Mortgage Loan or the interests of the Certificateholders
therein, it shall give prompt written notice of such Breach or Defect to the
Depositor, the Trustee, the Servicer, the Special Servicer and the Sellers and
shall request that the Seller not later than the earlier of 90 days from the
receipt by the Seller of such notice or discovery by the Seller of such Breach
or Defect (subject to the second succeeding paragraph, the "Initial Resolution
Period"), (i) cure such Breach or Defect in all material respects; (ii)
repurchase the affected Mortgage Loan at the applicable Purchase Price (as
defined in the Pooling and Servicing Agreement) or (iii) substitute one or more
Qualified Substitute Mortgage Loans (as defined in the Pooling and Servicing
Agreement) for such affected Mortgage Loan (provided that in no event shall any
substitution occur later than the second anniversary of the Closing Date) and
pay the Servicer for deposit into the Collection Account any Substitution
Shortfall Amount (as defined in the Pooling and Servicing Agreement) in
connection therewith; provided, however, that if (i) such material Breach or
material Defect is capable of being cured but not within the Initial Resolution
Period, (ii) such material Breach or material Defect does not cause the related
Mortgage Loan not to be a "qualified mortgage" (within the meaning of Section
860G(a)(3) of the Code), (iii) the Seller has commenced and is diligently
proceeding with the cure of such material Breach or material Defect within the
Initial Resolution Period and (iv) the Seller has delivered to the Rating
Agencies and the Trustee an Officer's Certificate that describes the reasons
that the cure was not effected within the Initial Resolution Period and the
actions that it proposes to take to effect the cure and that states that it
anticipates the cure will be effected within the additional 90-day period, then
the Seller shall have an additional 90 days to cure such material Defect or
material Breach. With respect to any substitution of one or more Qualified
Substitute Mortgage Loans for a Mortgage Loan hereunder, (A) no such
substitution may be made in any calendar month after the Determination Date for
such month; (B) scheduled payments of principal and interest due with respect to
the Qualified Substitute Mortgage Loan(s) after the related date of substitution
shall be part of the Trust Fund; and (C) scheduled payments of principal and
interest due with respect to such Qualified Substitute Mortgage Loan(s) on or
prior to the related date of substitution shall not be part of the Trust Fund,
and the Seller shall be entitled to receive such payments promptly following
receipt by the Servicer or Special Servicer, as applicable, under the Pooling
and Servicing Agreement.

            Any of the following will cause a document in the Mortgage File to
be deemed to have a "Defect" and to be conclusively presumed to materially and
adversely affect the interests of Certificateholders in a Mortgage Loan and to
be deemed to materially and adversely affect the interest of the
Certificateholders in and the value of a Mortgage Loan: (a) the absence from the
Mortgage File of the original signed Note, unless the Mortgage File contains a
signed lost note affidavit and indemnity that appears to be regular on its face;
(b) the absence from the Mortgage File of the original signed Mortgage that
appears to be regular on its face, unless there is included in the Mortgage File
a certified copy of the Mortgage as recorded or as sent for recordation,
together with a certificate stating that the original signed Mortgage was sent
for recordation; (c) the absence from the Mortgage File of the item called for
by paragraph (ix) of the definition of Mortgage File; (d) the absence from the
Mortgage File of any intervening assignments required to create a complete chain
of assignment to the Trustee on behalf of the Trust, unless there is included in
the Mortgage File a certified copy of the intervening assignment and a
certificate stating that the original intervening assignments were sent for
recordation; or (e) the absence from the Mortgage File of any required original
letter of credit.

            Any Defect or Breach which causes any Mortgage Loan not to be a
"qualified mortgage" (within the meaning of Section 860G(a)(3) of the Code)
shall be deemed to materially and adversely affect the interest of
Certificateholders therein and the Initial Resolution Period for the affected
Mortgage Loan shall be 90 days following the earlier of the Seller's receipt of
notice pursuant to this Section 7 or its discovery of such Defect or Breach
(which period shall not be subject to extension).

            If the Seller does not, as required by this Section 7, correct or
cure a material Breach or a material Defect in all material respects within the
applicable Initial Resolution Period (as extended pursuant to this Section 7),
or if such Breach or Defect is not capable of being so corrected or cured with
such period, then the Seller shall purchase or substitute for the affected
Mortgage Loan as provided in this Section 7. If (i) any Mortgage Loan is
required to be repurchased or substituted for as provided above, (ii) such
Mortgage Loan is a Crossed Loan that is a part of a Mortgage Group (as defined
below) and (iii) the applicable Breach or Defect does not constitute a Breach or
Defect, as the case may be, as to any other Crossed Loan in such Mortgage Group
(without regard to this paragraph), then the applicable Breach or Defect, as the
case may be, will be deemed to constitute a Breach or Defect, as the case may
be, as to any other Crossed Loan in the Mortgage Group for purposes of the above
provisions, and the Seller will be required to repurchase or substitute for such
other Crossed Loan(s) in the related Mortgage Group in accordance with the
provisions of this Section 7 unless such other Crossed Loans satisfy the Crossed
Loan Repurchase Criteria (as defined in the Pooling and Servicing Agreement). In
the event that one or more of such other Crossed Loans satisfy the Crossed Loan
Repurchase Criteria, the Seller may elect either to repurchase or substitute for
only the affected Crossed Loan as to which the related Breach or Defect exists
or to repurchase or substitute for all of the Crossed Loans in the related
Mortgage Group. The Seller shall be responsible for the cost of any Appraisal
required to be obtained by the Servicer to determine if the Crossed Loan
Repurchase Criteria have been satisfied, so long as the scope and cost of such
Appraisal has been approved by the Seller (such approval not to be unreasonably
withheld). For purposes of this paragraph, a "Mortgage Group" is any group of
Mortgage Loans identified as a Mortgage Group on Schedule III to this Agreement.

            Notwithstanding the foregoing, if there is a material Breach or
material Defect with respect to one or more Mortgaged Properties (but not all of
the Mortgaged Properties) with respect to a Mortgage Loan, the Seller will not
be obligated to repurchase or substitute for the Mortgage Loan if the affected
Mortgaged Property may be released pursuant to the terms of any partial release
provisions in the related Mortgage Loan Documents and the remaining Mortgaged
Property(ies) satisfy the requirements, if any, set forth in the Mortgage Loan
Documents and the Seller provides an opinion of counsel to the effect that such
partial release would not cause an Adverse REMIC Event (as defined in the
Pooling and Servicing Agreement) to occur and the Seller pays (or causes to be
paid) the applicable release price required under the Mortgage Loan Documents.

            The Purchase Price or Substitution Shortfall Amount for any
repurchased or substituted Mortgage Loan shall be payable to the Depositor or,
subsequent to the assignment of the Mortgage Loans to the Trustee, the Trustee
as its assignee, by wire transfer of immediately available funds to the account
designated by the Depositor or the Trustee, as the case may be, and the
Depositor or the Trustee, as the case may be, upon receipt of such funds, shall
promptly release the related Mortgage File and Servicer File or cause them to be
released, to Seller and shall execute and deliver such instruments of transfer
or assignment as shall be necessary to vest in the Seller the legal and
beneficial ownership of such Mortgage Loan (including any property acquired in
respect thereof or proceeds of any insurance policy with respect thereto) and
the related Mortgage Loan Documents.

            It is understood and agreed that the obligations of the Seller set
forth in this Section 7 to cure, substitute for or repurchase a Mortgage Loan
listed on Schedule II-A hereto constitute the sole remedies available to the
Depositor and its successors and assigns respecting any Breach or Defect
affecting such Mortgage Loan.

            Section 7 of the Owner Trust Certificate Purchase Agreement provides
the sole remedy available to the Depositor respecting any breach of
representations, warranties or covenants contained in such agreement or any
document defect, in either case, with respect to the Mortgage Loans described in
Schedule II-B hereto and neither the Depositor nor any assignee of the Depositor
shall have any remedies against the Seller with respect to any such breach or
defect.

            Section 8. Crossed Loans. With respect to any Crossed Loan conveyed
hereunder, to the extent that the Seller repurchases or substitutes for an
affected Crossed Loan in the manner prescribed above while the Trustee continues
to hold any related Crossed Loans, the Seller and the Depositor (on behalf of
its successors and assigns) agree to forbear from enforcing any remedies against
the other's Primary Collateral, but each is permitted to exercise remedies
against the Primary Collateral securing its respective affected Crossed Loans,
including, with respect to the Trustee, the Primary Collateral securing Mortgage
Loans still held by the Trustee, so long as such exercise does not impair the
ability of the other party to exercise its remedies against its Primary
Collateral. If the exercise of remedies by one party would impair the ability of
the other party to exercise its remedies with respect to the Primary Collateral
securing the Crossed Loans held by such party, then both parties agree to
forbear from exercising such remedies until the Mortgage Loan Documents
evidencing and securing the relevant Mortgage Loans can be modified in a manner
that complies with this Agreement to remove the threat of impairment as a result
of the exercise of remedies. Any reserve or other cash collateral or letters of
credit securing the Crossed Loans shall be allocated between such Mortgage Loans
in accordance with the Mortgage Loan Documents, or otherwise on a pro rata basis
based upon their outstanding Stated Principal Balances. All other terms of the
Mortgage Loans shall remain in full force and effect, without any modification
thereof.

            Section 9. Rating Agency Fees; Costs and Expenses Associated with a
Defeasance. The Seller shall pay all Rating Agency fees associated with an
assumption of a Mortgage Loan to the extent such fees have not been paid by the
related Borrower and such Borrower is not required to pay them under the terms
of the related Mortgage Loan Documents in effect on or before the Closing Date.
The Seller shall pay all reasonable costs and expenses associated with a
defeasance of a Mortgage Loan to the extent such costs and expenses have not
been paid by the related Borrower and such Borrower is not required to pay them
under the terms of the related Mortgage Loan Documents in effect on or before
the Closing Date.

            Section 10. Representations and Warranties of Depositor. Depositor
hereby represents and warrants to Seller as of the date hereof, as follows:

            (a) Depositor is duly organized and is validly existing as a
corporation in good standing under the laws of the State of Delaware, with full
corporate power and authority to own its assets and conduct its business as it
is conducted, and is duly qualified as a foreign corporation in good standing in
all jurisdictions in which the ownership or lease of its property or the conduct
of its business requires such qualification (except where the failure to qualify
would not have a materially adverse effect on the consummation of any
transactions contemplated by this Agreement).

            (b) The execution and delivery by Depositor of this Agreement and
the performance of Depositor's obligations hereunder are within the corporate
power of Depositor and have been duly authorized by Depositor and neither the
execution and delivery by Depositor of this Agreement nor the compliance by
Depositor with the provisions hereof, nor the consummation by Depositor of the
transactions contemplated by this Agreement, will (i) conflict with or result in
a breach of, or constitute a default under, the certificate of incorporation or
by-laws of Depositor or, after giving effect to the consents or taking of the
actions contemplated by clause (ii) of this paragraph (b), any of the provisions
of any law, governmental rule, regulation, judgment, decree or order binding on
Depositor or its properties, or any of the provisions of any material indenture
or mortgage or any other material contract or other instrument to which
Depositor is a party or by which it is bound or result in the creation or
imposition of any lien, charge or encumbrance upon any of its properties
pursuant to the terms of any such indenture, mortgage, contract or other
instrument or (ii) require the consent of or notice to, or any filing with any
person, entity or governmental body, which has not been obtained or made by
Depositor, except where, in any of the instances contemplated by clause (i)
above or this clause (ii), the failure to do so will not have a material and
adverse effect on the consummation of any transactions contemplated by this
Agreement.

            (c) This Agreement has been duly executed and delivered by Depositor
and this Agreement constitutes a legal, valid and binding instrument,
enforceable against Depositor in accordance with its terms, subject, as to the
enforcement of remedies, to applicable bankruptcy, reorganization, insolvency,
moratorium and other laws affecting the rights of creditors generally and to
general principles of equity and the discretion of the court (regardless of
whether enforcement of such remedies is considered in a proceeding in equity or
at law) and, as to rights of indemnification hereunder, subject to limitations
of public policy under applicable securities laws.

            (d) There is no litigation, charge, investigation, action, suit or
proceeding by or before any court, regulatory authority or governmental agency
or body pending or, to the knowledge of Depositor, threatened against Depositor
the outcome of which could be reasonably expected to materially and adversely
affect the consummation of any transactions contemplated by this Agreement.

            Section 11. Survival of Certain Representations, Warranties and
Covenants. The respective representations and warranties set forth in or made
pursuant to this Agreement, and the respective obligations of the parties hereto
under Sections 7 and 11 of this Agreement, will remain in full force and effect,
regardless of any investigation or statement as to the result thereof made by or
on behalf of any party and will survive payment for the various transfers
referred to herein and delivery of the Certificates or termination of this
Agreement.

            Section 12. [Reserved]

            Section 13. Expenses; Recording Costs. Seller agrees to reimburse
the Trustee or its designee all recording and filing fees incurred in connection
with the recording or filing of the Mortgage Loan Documents listed in Section 3
of this Agreement.

            Section 14. Notices. All communications hereunder will be in writing
and effective only upon receipt, and, (a) if sent to Depositor, will be mailed,
delivered or telecopied and confirmed to it at Credit Suisse First Boston
Mortgage Securities Corp., Eleven Madison Avenue, 5th Floor, New York, New York
10010, Attention: Allan J. Baum, Telecopy No.: (212) 325-8162; and (b) if sent
to Seller, will be mailed, delivered or telecopied to it at Column Financial,
Inc., 3414 Peachtree Road, N.E., Suite 1140, Atlanta, Georgia 30326, Attention:
President, Telecopy No.: (404) 239-0419.

            Section 15. Examination of Mortgage Files. Upon reasonable notice,
Seller, prior to the Closing Date, will make the Mortgage Files available to
Depositor or its agent for examination during normal business hours at Seller's
offices or such other location as shall otherwise be agreed upon by Depositor
and Seller. The fact that Depositor or its agent has conducted or has failed to
conduct any partial or complete examination of the Mortgage Files shall not
affect the rights of Depositor or the Trustee (for the benefit of the
Certificateholders) to demand cure, repurchase, or other relief as provided
herein.

            Section 16. Successors. This Agreement shall inure to the benefit of
and shall be binding upon Seller and Depositor and their respective successors,
permitted assigns and legal representatives, and nothing expressed in this
Agreement is intended or shall be construed to give any other person any legal
or equitable right, remedy or claim under or in respect of this Agreement, or
any provisions herein contained, this Agreement and all conditions and
provisions hereof being intended to be and being for the sole and exclusive
benefit of such persons and for the benefit of no other person; it being
understood that (a) the indemnities of Seller contained in that certain
Indemnification Agreement dated August 17, 2001 among Seller, Depositor and the
Underwriters, subject to all limitations therein contained, shall also be for
the benefit of the officers and directors of Depositor, the Underwriters and the
Initial Purchaser and any person or persons who control Depositor, the
Underwriters and the Initial Purchaser within the meaning of Section 15 of the
Securities Act or Section 20 of the 1934 Act, and (b) the rights of Depositor
pursuant to this Agreement, subject to all limitations herein contained,
including those set forth in Section 9 of this Agreement, may be assigned to the
Trustee as may be required to effect the purposes of the Pooling and Servicing
Agreement and, upon such assignment, the Trustee shall succeed to such rights of
Depositor hereunder. No owner of a Certificate issued pursuant to the Pooling
and Servicing Agreement shall be deemed a successor because of such ownership.

            Section 17. Governing Law. THIS AGREEMENT SHALL BE GOVERNED AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK APPLICABLE TO
AGREEMENTS TO BE MADE AND PERFORMED ENTIRELY WITHIN SUCH STATE WITHOUT GIVING
EFFECT TO CHOICE OF LAW PRINCIPLES.

            Section 18. Severability. If any provision of this Agreement shall
be prohibited or invalid under applicable law, this Agreement shall be
ineffective only to such extent, without invalidating the remainder of this
Agreement.

            Section 19. Further Assurances. Depositor and Seller agree to
execute and deliver such instruments and take such actions as the other parties
may, from time to time, reasonably request in order to effectuate the purpose
and to carry out the terms of this Agreement.

            Section 20. Counterparts. This Agreement may be executed in
counterparts (and by each of the parties hereto on different counterparts), each
of which when so executed and delivered will be an original, and all of which
together will be deemed to constitute but one and the same instrument.

            Section 21. Treatment as Security Agreement. It is the express
intent of the parties hereto that the conveyance of the Mortgage Loans by Seller
to Depositor as provided in this Agreement be, and be construed as, a sale of
the Mortgage Loans by Seller to Depositor. It is, further, not the intention of
the parties that such conveyance be deemed a pledge of the Mortgage Loans by
Seller to Depositor to secure a debt or other obligation of Seller. However, in
the event that, notwithstanding the intent of the parties, the Mortgage Loans
are held to be property of Seller or if for any reason this Agreement is held or
deemed to create a security interest in the Mortgage Loans:

            (a) this Agreement shall hereby create a security agreement within
the meaning of Articles 8 and 9 of the Uniform Commercial Code in effect in the
applicable state;

            (b) the conveyance provided for in this Agreement shall hereby grant
from Seller to Depositor a security interest in and to all of Seller's right,
title, and interest, whether now owned or hereafter acquired, in and to:

            (i) all accounts, contract rights, general intangibles, chattel
      paper, instruments, documents, money, deposit accounts, certificates of
      deposit, goods, letters of credit, advices of credit and investment
      property consisting of, arising from or relating to any of the property
      described in the Mortgage Loans, including the related Notes, Mortgages
      and title, hazard and primary mortgage insurance policies identified on
      the Mortgage Loan Schedule, including all replacement Mortgage Loans, and
      all distributions with respect thereto payable after the Cut-off Date;

            (ii) all accounts, contract rights, general intangibles, chattel
      paper, instruments, documents, money, deposit accounts, certificates of
      deposit, goods, letters of credit, advices of credit and investment
      property arising from or by virtue of the disposition of, or collections
      with respect to, or insurance proceeds payable with respect to, or claims
      against other persons with respect to, all or any part of the collateral
      described in (i) above (including any accrued discount realized on
      liquidation of any investment purchased at a discount), in each case,
      payable after the Cut-off Date; and

            (iii) all cash and non-cash proceeds of the collateral described in
      (i) and (ii) above payable after the Cut-off Date;

            (c) the possession by Depositor or its assignee of the Notes and
such other goods, letters of credit, advices of credit, instruments, money,
documents, chattel paper or certificated securities shall be deemed to be
possession by the secured party or possession by a purchaser or a person
designated by him or her, for purposes of perfecting the security interest
pursuant to the Uniform Commercial Code (including, without limitation, Sections
9-306, 9-313 and 9-314 thereof) as in force in the relevant jurisdiction; and

            (d) notifications to persons holding such property, and
acknowledgments, receipts, confirmations from persons holding such property,
shall be deemed to be notifications to, or acknowledgments, receipts or
confirmations from, financial intermediaries, bailees or agents of, or persons
holding for (as applicable), Depositor or its assignee for the purpose of
perfecting such security interest under applicable law. The Seller at the
direction of the Depositor or its assignee, shall, to the extent consistent with
this Agreement, take such actions as may be necessary to ensure that, if this
Agreement were deemed to create a security interest in the Mortgage Loans and
the proceeds thereof, such security interest would be a perfected security
interest of first priority under applicable law and will be maintained as such
throughout the term of this Agreement. In connection herewith, Depositor and its
assignee shall have all of the rights and remedies of a secured party and
creditor under the Uniform Commercial Code as in force in the relevant
jurisdiction.

            Section 22. Recordation of Agreement. To the extent permitted by
applicable law, this Agreement is subject to recordation following the Closing
Date in all appropriate public offices for real property records in all the
counties or other comparable jurisdictions in which any or all of the properties
subject to the Mortgages are situated, and in any other appropriate public
recording office or elsewhere, such recordation to be effected by Seller at
Seller's expense at the direction of Depositor accompanied by an Opinion of
Counsel to the effect that such recordation materially and beneficially affects
the interests of Depositor.

                                      * * *

<PAGE>

            IN WITNESS WHEREOF, the parties hereto have caused this Mortgage
Loan Purchase Agreement to be duly executed and delivered as the date first
above written.

                                       COLUMN FINANCIAL, INC.,
                                       as Seller

                                       By: ___________________________________
                                           Name:
                                           Title:

                                       CREDIT SUISSE FIRST BOSTON MORTGAGE
                                       SECURITIES CORP.,
                                       as Depositor

                                       By: ___________________________________
                                           Name:
                                           Title:   Vice President

<PAGE>

                                                                      SCHEDULE I

                          SCHEDULE OF TRANSACTION TERMS

            This Schedule of Transaction Terms is appended to and incorporated
by reference in the Mortgage Loan Purchase Agreement (the "Agreement"), dated as
of August 1, 2001, between Column Financial, Inc. (the "Seller") and Credit
Suisse First Boston Mortgage Securities Corp. (the "Depositor"). Capitalized
terms used herein without definition have the meanings given them in or by
reference in the Agreement or, if not defined in the Agreement, in the Pooling
and Servicing Agreement, the Underwriting Agreement.

            "Affiliate" means with respect to any specified Person, any other
Person controlling or controlled by or under common control with such specified
Person.

            "Borrower" means the borrower under the Mortgage Loan.

            "Certificate Purchase Agreement" means the Certificate Purchase
Agreement, dated August 17, 2001, between Depositor and the Initial Purchasers.

            "Certificates" means each class of the Credit Suisse First Boston
Mortgage Securities Corp. Commercial Mortgage Pass-Through Certificates, Series
2001-CP4.

            "Closing Date" means August 28, 2001.

            "Code" means the Internal Revenue Code of 1986, as amended.

            "Crossed Loan" means any Mortgage Loan which is cross-defaulted and
cross-collateralized with any other Mortgage Loan.

            "Cut-off Date" means, the applicable Due Date for each Mortgage Loan
occurring in August 2001.

            "Environmental Report" means the environmental audit report with
respect to each Mortgaged Property delivered to Seller in connection with the
related Mortgage, if any.

            "Exception Report" means exceptions with respect to the
representations and warranties made by the Seller as to the Mortgage Loans in
Section 6(a)(xii) and under the written certificate described in Section
4(b)(iii), which exceptions are set forth in Schedule V attached hereto and made
a part hereof.

            "Initial Purchasers" means Credit Suisse First Boston Corporation
and PNC Capital Markets, Inc.

            "Loan Agreement" means, with respect to any Mortgage Loan, the loan
agreement, if any, between the Originator and the Borrower, pursuant to which
such Mortgage Loan was made.

            "Mortgage Loan Purchase Price" means the amount described in Section
2 of the Agreement.

            "Mortgage Loan Documents" means, collectively, the documents and
instruments pertaining to a Mortgage Loan to be included in either the related
Mortgage File or the related Servicer File.

            "Mortgage File" means, collectively, the documents and instruments
pertaining to a Mortgage Loan required to be included in the related Mortgage
File pursuant to Section 3 (subject to the proviso in Section 1).

            "Mortgage Loans" means the mortgage loans to be sold to Depositor
pursuant to the Agreement, specifically identified in the Mortgage Loan Schedule
to the Agreement.

            "Offered Certificates" means the Class A-1, Class A-2, Class A-3,
Class A-4, Class B, Class C and Class D Certificates.

            "Offering Circular" means the confidential offering circular dated
August 17, 2001, describing certain classes of the Certificates.

            "Originator" means any institution which originated a Mortgage Loan
for a related Borrower.

            "PNC Owner Trust Certificate Purchase Agreement" means, with respect
to the Mortgage Loans listed on Schedule II-B hereto, that certain Owner Trust
Certificate Purchase Agreement, dated as of August 1, 2001, between the Seller,
as purchaser, and Midland Loan Services, Inc. and Anthracite Capital, Inc., as
sellers, relating to the transfer to the Seller of Owner Trust Certificates
representing ownership of an owner trust the assets of which are certain
mortgage loans, the liquidation by the Seller of such owner trust resulting in
the distribution of such mortgage loans to the Seller, and under which Midland
Loan Services, Inc. made certain representations and warranties relating to the
Mortgage Loans listed on Schedule II-B hereto.

            "Pooling and Servicing Agreement" means the Pooling and Servicing
Agreement creating the Trust Fund and the interests therein, dated as of August
1, 2001, among the Servicer, the Special Servicer, Depositor and the Trustee,
including the Mortgage Loan Schedule annexed thereto.

            "Primary Collateral" means with respect to any Crossed Loan, that
portion of the Mortgaged Property designated as directly securing such Crossed
Loan and excluding any Mortgaged Property as to which the related lien may only
be foreclosed upon by exercise of the cross-collaterization provisions of such
Crossed Loan.

            "Prospectus" means the Prospectus, dated March 5, 2001.

            "Prospectus Supplement" means the Prospectus Supplement, dated
August 17, 2001, relating to the Offered Certificates.

            "Servicer File" means, collectively, all documents, records and
copies pertaining to a Mortgage Loan listed on Schedule II-A which are required
to be included in the related Servicer File pursuant to Section 3 (subject to
the proviso in Section 1).

            "Underwriters" means Credit Suisse First Boston Corporation, PNC
Capital Markets, Inc., Lehman Brothers Inc. and Salomon Smith Barney, Inc.

            "Underwriting Agreement" means the Underwriting Agreement, dated
August 17, 2001, between Depositor and the Underwriters.

<PAGE>

                                                                  EXECUTION COPY

                                                                   SCHEDULE II-A

                     MORTGAGE LOAN SCHEDULE FOR COLUMN LOANS

<PAGE>

                                                                  EXECUTION COPY

                                                                   SCHEDULE II-B

                      MORTGAGE LOAN SCHEDULE FOR PNC LOANS

<PAGE>

                                                                  EXECUTION COPY

                                                                    SCHEDULE III

                   MORTGAGE LOANS CONSTITUTING MORTGAGE GROUPS

1.    Somerset Park loan (loan number 7) and Somerset Center & Somerset Place
      loan (loan number 8)

<PAGE>

                                                                  EXECUTION COPY

                                                                     SCHEDULE IV

                         MORTGAGE LOANS WITH LOST NOTES

                                     [NONE]

<PAGE>

                                                                  EXECUTION COPY

                                                                      SCHEDULE V

                             EXCEPTIONS TO SELLER'S
                         REPRESENTATIONS AND WARRANTIES

            Reference is made to the Representations and Warranties contained in
Exhibit A corresponding to the roman numerals listed below:

Exception to Section (v):

            Golf Terrace Apartments Phases I and II - The two satellite/cable TV
easements and agreements remain of record, although Borrower indicates they are
no longer in use and have terminated. Indemnitors indemnify lender against
potential claims by addition to "carve-out" provisions.

Exception to Section (xxv):

            Dauphine Apartments - This $3,500,000 loan was part of the small
balance program (normally less than $3,000,000). As such, no environmental
report was obtained, but an environmental insurance policy was obtained.

Exception to Section (xxix):

            Metro Town Square - With respect to section (c) of such
representation, the groundlease extends with options until December 31, 2025 and
the loan matures September 11, 2014, or a period of just less than eleven years.

Exception to Section (xxxvi):

            Holley Gardens - The borrower is an obligor under a $300,000 loan to
affiliates which is subject to a standstill and subordination agreement. In
addition, the Borrower may incur up to $250,000 of additional affiliate debt
(also subject to a standstill and subordination agreement).

Exceptions to Section (liii):

            Belcrest Realty GT1 - With respect to clause (v) of such
representation, the guarantor and not the Borrower is liable if any act results
in the property becoming an asset in a voluntary bankruptcy or insolvency
proceeding.

            Belcrest Realty GT7 - With respect to clause (v) of such
representation, the guarantor and not the Borrower is liable if any act results
in the property becoming an asset in a voluntary bankruptcy or insolvency
proceeding.

            Holley Gardens - The non-recourse carve-out exceptions do not
include (1) "willful acts of material waste" or (2) any act resulting in the
mortgaged property becoming an asset in a voluntary bankruptcy or insolvency
proceeding.

            Reservoir Corporate Center - The non-recourse carve-out exceptions
do not include (1) "willful acts of material waste" or (2) any act resulting in
the mortgaged property becoming an asset in a voluntary bankruptcy or insolvency
proceeding.

            Greentree Apartments - The non-recourse carve-out exceptions do not
include (1) "willful acts of material waste" or (2) any act resulting in the
mortgaged property becoming an asset in a voluntary bankruptcy or insolvency
proceeding.

Exceptions to Section (liv):

            Tanglewood - With respect to clause (iv) of such representation,
with the passage of the Anticipated Repayment Date, if the loan is not in
default, only 75% of the surplus cash flow (after all costs have been paid) is
applied to amortize the Mortgage Loan.

            Reservoir Corporate Center - With respect to clause (iv) of such
representation, with passage of the Anticipated Repayment Date, all cash flow is
applied (1) first to an operations and maintenance expense account from which
the Lender disburses approved operating expenses; (2) second to the TILC
Reserve; (3) third to the Impound Account (for taxes and insurance); (4) fourth
to the Debt Service Payment Reserve, and (5) fifth to the balance first to
outstanding principal, and then to accrued interest on the note.

<PAGE>

                                                                  EXECUTION COPY

EXHIBIT A

                    REPRESENTATIONS AND WARRANTIES OF SELLER
                          REGARDING THE MORTGAGE LOANS

            (i) Immediately prior to the sale, transfer and assignment to the
Depositor, no Note or Mortgage was subject to any assignment (other than
assignments which show a complete chain of assignment to the Seller),
participation or pledge, and the Seller had good and marketable title to, and
was the sole owner of, the related Mortgage Loan;

            (ii) The Seller has full right and authority to sell, assign and
transfer such Mortgage Loan and the assignment to the Depositor constitutes a
legal, valid and binding assignment of such Mortgage Loan;

            (iii) The Seller is transferring such Mortgage Loan free and clear
of any and all liens, pledges, charges or security interests of any nature
encumbering such Mortgage Loan;

            (iv) Each related Note, Mortgage, assignment of leases (if any) and
other agreement executed by or for the benefit of the related borrower, any
guarantor or their successors or assigns in connection with such Mortgage Loan
is the legal, valid and binding obligation of the related borrower, enforceable
in accordance with its terms, except as such enforcement may be limited by
bankruptcy, insolvency, reorganization, moratorium or other laws affecting the
enforcement of creditors' rights or by general principles of equity (regardless
of whether such enforceability is considered in a proceeding in equity or at
law); and there is no valid defense, counterclaim, or right of rescission
available to the related borrower with respect to such Note, Mortgage,
assignment of leases and other agreements, except as the enforcement thereof may
be limited by bankruptcy, insolvency, reorganization, moratorium or other laws
affecting the enforcement of creditors' rights or by general principles of
equity (regardless of whether such enforceability is considered in a proceeding
in equity or at law);

            (v) Each related assignment of leases creates a valid first priority
collateral assignment of, or a valid first priority lien or security interest
in, certain rights under the related lease or leases, subject only to a license
granted to the related borrower to exercise certain rights and to perform
certain obligations of the lessor under such lease or leases, including the
right to operate the related leased property, except as the enforcement thereof
may be limited by bankruptcy, insolvency, reorganization, moratorium or other
laws affecting the enforcement of creditors' rights or by general principles of
equity (regardless of whether such enforceability is considered in a proceeding
in equity or at law); no person other than the related borrower owns any
interest in any payments due under such lease or leases that is superior to or
of equal priority with the lender's interest therein;

            (vi) Each related assignment of Mortgage from the Seller to the
Depositor and related assignment of the assignment of leases, if any, or
assignment of any other agreement executed by or for the benefit of the related
borrower, any guarantor or their successors or assigns in connection with such
Mortgage Loan from the Seller to the Depositor constitutes the legal, valid and
binding assignment from the Seller to the Depositor, except as the enforcement
thereof may be limited by bankruptcy, insolvency, reorganization, liquidation,
receivership, moratorium or other laws relating to or affecting the enforcement
of creditors' rights or by general principles of equity (regardless of whether
such enforceability is considered in a proceeding in equity or at law);

            (vii) Since origination, and except as set forth in the related
mortgage file, (a) such Mortgage Loan has not been modified, altered, satisfied,
canceled, subordinated or rescinded and (b) each related Mortgaged Property has
not been released from the lien of the related Mortgage in any manner which
materially interferes with the security intended to be provided by such
Mortgage;

            (viii) Each related Mortgage is a valid and enforceable first lien
on the related Mortgaged Property (subject to Permitted Encumbrances (as defined
below)), except as the enforcement thereof may be limited by bankruptcy,
insolvency, reorganization, moratorium or other laws affecting the enforcement
of creditors' rights or by general principles of equity (regardless of whether
such enforceability is considered in a proceeding in equity or at law); and such
Mortgaged Property is free and clear of any mechanics' and materialmen's liens
which are prior to or equal with the lien of the related Mortgage, except those
which are insured against by a lender's title insurance policy (as described
below). A UCC financing statement has been filed and/or recorded (or sent for
filing or recording) in all places necessary to perfect a valid security
interest in the personal property necessary to operate the Mortgaged Property;
any security agreement, chattel mortgage or equivalent document related to and
delivered in connection with the Mortgage Loan establishes and creates a valid
and enforceable lien on property described therein, except as such enforcement
may be limited by bankruptcy, insolvency, reorganization, moratorium or other
laws affecting the enforcement of creditors' rights or by general principles of
equity (regardless of whether such enforceability is considered in a proceeding
in equity or at law);

            (ix) The Seller has not taken any action that would cause the
representations and warranties made by the related borrower in the related
Mortgage Loan Documents not to be true;

            (x) The Seller has no knowledge that the material representations
and warranties made by the related borrower in the related Mortgage Loan
Documents are not true in any material respect;

            (xi) The lien of each related Mortgage is a first priority lien on
the fee or leasehold interest of the related borrower in the principal amount of
such Mortgage Loan or allocated loan amount of the portions of the Mortgaged
Property covered thereby (as set forth in the related Mortgage) after all
advances of principal and is insured by an ALTA lender's title insurance policy
(or a binding commitment therefor), or its equivalent as adopted in the
applicable jurisdiction, insuring the Seller and its successors and assigns as
to such lien, subject only to (a) the lien of current real property taxes,
ground rents, water charges, sewer rents and assessments not yet delinquent or
accruing interest or penalties, (b) covenants, conditions and restrictions,
rights of way, easements and other matters of public record, none of which,
individually or in the aggregate, materially interferes with the current use of
the Mortgaged Property or the security intended to be provided by such Mortgage
or with the borrower's ability to pay its obligations when they become due or
the value of the Mortgaged Property and (c) the exceptions (general and
specific) and exclusions set forth in such policy, none of which, individually
or in the aggregate, materially interferes with the current general use of the
Mortgaged Property or materially interferes with the security intended to be
provided by such Mortgage or with the related borrower's ability to pay its
obligations when they become due or the value of the Mortgaged Property (items
(a), (b) and (c) collectively, "Permitted Encumbrances"); the premium for such
policy was paid in full; such policy (or if it is yet to be issued, the coverage
to be afforded thereby) is issued by a title insurance company licensed to issue
policies in the state in which the related Mortgaged Property is located (unless
such state is Iowa) and is assignable (with the related Mortgage Loan) to the
Depositor and the Trustee without the consent of or any notification to the
insurer, and is in full force and effect upon the consummation of the
transactions contemplated by the Mortgage Loan Purchase Agreement; no claims
have been made under such policy and the Seller has not undertaken any action or
omitted to take any action, and has no knowledge of any such act or omission,
which would impair or diminish the coverage of such policy;

            (xii) The proceeds of such Mortgage Loan have been fully disbursed
and there is no requirement for future advances thereunder, and no future
advances have been made which are not reflected in the related mortgage file;

            (xiii) Except as set forth in a property inspection report or
engineering report prepared in connection with the origination of the Mortgage
Loan, as of the later of the date of origination of such Mortgage Loan or the
most recent inspection of the related Mortgaged Property by the Seller, as
applicable, and to the knowledge of Seller as of the date hereof, each related
Mortgaged Property is free of any material damage that would affect materially
and adversely the value of such Mortgaged Property as security for the Mortgage
Loan or reserves have been established to cover the costs to remediate such
damage and, as of the closing date for each Mortgage Loan and, to the Seller's
knowledge, as of the date hereof, there is no proceeding pending for the total
or partial condemnation of such Mortgaged Property that would have a material
adverse effect on the value of the Mortgaged Property;

            (xiv) The Seller has inspected or caused to be inspected each
related Mortgaged Property within the past twelve months, or the originator of
the Mortgage Loan inspected or caused to be inspected each related Mortgage
Property within three months of origination of the Mortgage Loan;

            (xv) No Mortgage Loan has a shared appreciation feature, any other
contingent interest feature or a negative amortization feature other than the
ARD Loans which may have negative amortization from and after the Anticipated
Repayment Date;

            (xvi) Each Mortgage Loan is a whole loan and contains no equity
participation by Seller;

            (xvii) The Mortgage Rate (exclusive of any default interest, late
charges, or prepayment premiums) of such Mortgage Loan complied as of the date
of origination with, or was exempt from, applicable state or federal laws,
regulations and other requirements pertaining to usury. Except to the extent any
noncompliance did not materially and adversely affect the value of the related
Mortgaged Property, the security provided by the Mortgage or the related
borrower's operations at the related Mortgaged Property, any and all other
requirements of any federal, state or local laws, including, without limitation,
truth-in-lending, real estate settlement procedures, equal credit opportunity or
disclosure laws, applicable to such Mortgage Loan have been complied with as of
the date of origination of such Mortgage Loan;

            (xviii) Neither the Seller nor to the Seller's knowledge, any
originator, committed any fraudulent acts during the origination process of any
Mortgage Loan and the origination, servicing and collection of each Mortgage
Loan is in all respects legal, proper and prudent in accordance with customary
commercial mortgage lending standards, and no other person has been granted or
conveyed the right to service the Mortgage Loans or receive any consideration in
connection therewith, except as provided in the Pooling and Servicing Agreement
or any permitted subservicing agreements;

            (xix) All taxes and governmental assessments that became due and
owing prior to the date hereof with respect to each related Mortgaged Property
and that are or may become a lien of priority equal to or higher than the lien
of the related Mortgage have been paid or an escrow of funds has been
established and such escrow (including all escrow payments required to be made
prior to the delinquency of such taxes and assessments) is sufficient to cover
the payment of such taxes and assessments;

            (xx) All escrow deposits and payments required pursuant to each
Mortgage Loan are in the possession, or under the control, of the Seller or its
agent and there are no deficiencies (subject to any applicable grace or cure
periods) in connection therewith and all such escrows and deposits are being
conveyed by the Seller to the Depositor and identified as such with appropriate
detail;

            (xxi) Each related Mortgaged Property is insured by a fire and
extended perils insurance policy, issued by an insurer meeting the requirements
of the Pooling and Servicing Agreement, in an amount not less than the lesser of
the principal amount of the related Mortgage Loan and the replacement cost (with
no deduction for physical depreciation) and not less than the amount necessary
to avoid the operation of any co-insurance provisions with respect to the
related Mortgaged Property; each related Mortgaged Property is also covered by
business interruption or rental loss insurance which covers a period of not less
than 12 months and comprehensive general liability insurance in amounts
generally required by prudent commercial mortgage lenders for similar
properties; all premiums on such insurance policies required to be paid as of
the date hereof have been paid; such insurance policies require prior notice to
the insured of termination or cancellation, and no such notice has been received
by the Seller; such insurance names the lender under the Mortgage Loan and its
successors and assigns as a named or additional insured; each related Mortgage
Loan obligates the related borrower to maintain all such insurance and, at such
borrower's failure to do so, authorizes the lender to maintain such insurance at
the borrower's cost and expense and to seek reimbursement therefor from such
borrower;

            (xxii) There is no monetary default, breach, violation or event of
acceleration existing under the related Mortgage Loan. To the Seller's
knowledge, there is no (a) non-monetary default, breach, violation or event of
acceleration existing under the related Mortgage Loan or (b) event (other than
payments due but not yet delinquent) which, with the passage of time or with
notice and the expiration of any grace or cure period, would and does constitute
a default, breach, violation or event of acceleration, which default, breach,
violation or event of acceleration, in the case of either (a) or (b), materially
and adversely affects the value of the Mortgage Loan or the related Mortgaged
Property; provided, however, that this representation and warranty does not
address or otherwise cover any default, breach, violation or event of
acceleration that specifically pertains to any matter otherwise covered by any
other representation or warranty made by the Seller in any of paragraphs (xiii),
(xix), (xxiii), (xxv), (xxvii), and (xxix) of this Exhibit A-1;

            (xxiii) No Mortgage Loan has been more than 30 days delinquent in
making required payments since origination and as of the Cut-off Date no
Mortgage Loan is 30 or more days delinquent in making required payments;

            (xxiv) (a) Each related Mortgage contains provisions so as to render
the rights and remedies of the holder thereof adequate for the practical
realization against the Mortgaged Property of the principal benefits of the
security, including realization by judicial or, if applicable, non-judicial
foreclosure, and (b) there is no exemption available to the borrower which would
interfere with such right to foreclose, except, in the case of either (a) or
(b), as the enforcement of the Mortgage may be limited by bankruptcy,
insolvency, reorganization, moratorium, redemption or other laws affecting the
enforcement of creditors' rights or by general principles of equity (regardless
of whether such enforceability is considered in a proceeding in equity or at
law). To the Seller's knowledge, no borrower is a debtor in a state or federal
bankruptcy or insolvency proceeding;

            (xxv) At origination, each borrower represented and warranted in all
material respects that to its knowledge, except as set forth in certain
environmental reports, it has not used, caused or permitted to exist and will
not use, cause or permit to exist on the related Mortgaged Property any
hazardous materials in any manner which violates federal, state or local laws,
ordinances, regulations, orders, directives or policies governing the use,
storage, treatment, transportation, manufacture, refinement, handling,
production or disposal of hazardous materials or other environmental laws; the
related borrower or an affiliate thereof agreed to indemnify, defend and hold
the mortgagee and its successors and assigns harmless from and against losses,
liabilities, damages, injuries, penalties, fines, expenses, and claims of any
kind whatsoever (including attorneys' fees and costs) paid, incurred or suffered
by, or asserted against, any such party resulting from a breach of the foregoing
representations, warranties or covenants given by the borrower in connection
with such Mortgage Loan. A Phase I environmental report and with respect to
certain Mortgage Loans, a Phase II environmental report, was conducted by a
reputable environmental engineer in connection with such Mortgage Loan, which
report did not indicate any material non-compliance with applicable
environmental laws or material existence of hazardous materials or, if any
material non-compliance or material existence of hazardous materials was
indicated in any such report, then at least one of the following statements is
true: (A) funds reasonably estimated to be sufficient to cover the cost to cure
any material non-compliance with applicable environmental laws or material
existence of hazardous materials have been escrowed by the related borrower and
held by the related mortgagee; (B) an operations or maintenance plan has been
required to be instituted by the related borrower; (C) the environmental
condition identified in the related environmental report was remediated or
abated in all material respects prior to the date hereof and a no further action
or closure letter was obtained from the applicable governmental regulatory
authority (or the environmental issue affecting the related Mortgaged Property
was otherwise listed by such governmental authority as "closed"); or (D) a
lender's environmental insurance policy was obtained and is a part of the
related mortgage file. Notwithstanding the preceding sentence, with respect to
certain Mortgage Loans with an original principal balance of less than
$3,000,000, no environmental report may have been obtained, but a lender's
secured creditor impairment environmental insurance policy was obtained with
respect to each such Mortgage Loan and is a part of the related mortgage file.
Each of such environmental insurance policies is in full force and effect, the
premiums for such policies have been paid in full and the Trustee is named as an
insured under each of such policies. To the best of the Seller's knowledge, in
reliance on such environmental reports and except as set forth in such
environmental reports, each Mortgaged Property is in material compliance with
all applicable federal, state and local environmental laws, and to the best of
the Seller's knowledge, no notice of violation of such laws has been issued by
any governmental agency or authority, except, in all cases, as indicated in such
environmental reports or other documents previously provided to the Rating
Agencies; and the Seller has not taken any action which would cause the
Mortgaged Property to not be in compliance with all federal, state and local
environmental laws pertaining to environmental hazards;

            (xxvi) (1) Each Mortgage Loan contains provisions for the
acceleration of the payment of the unpaid principal balance of such Mortgage
Loan if, without the consent of the holder of the Mortgage (and the Mortgage
requires the mortgagor to pay all fees and expenses associated with obtaining
such consent), the related Mortgaged Property is directly or indirectly
transferred or sold, and (2) except with respect to transfers of certain
interests in the related Borrower to persons already holding interests in the
Borrower, their family members, affiliated companies and other estate planning
related transfers that satisfy certain criteria specified in the related
Mortgage (which criteria is consistent with the practices of prudent commercial
mortgage lenders), each Mortgage Loan with a Stated Principal Balance of over
$20,000,000 also contains the provisions for the acceleration of the payment of
the unpaid principal balance of such Mortgage Loan if, without the consent of
the holder of the Mortgage, (and the Mortgage requires the mortgagor to pay all
fees and expenses associated with obtaining such consent) a majority interest in
the related Borrower is directly or indirectly transferred or sold;

            (xxvii) All improvements included in the related appraisal are
within the boundaries of the related Mortgaged Property, except for
encroachments onto adjoining parcels for which the Seller has obtained title
insurance against losses arising therefrom or that do not materially and
adversely affect the value of such Mortgaged Property. No improvements on
adjoining parcels encroach onto the related Mortgaged Property except for
encroachments that do not materially and adversely affect the value of such
Mortgaged Property, the security provided by the Mortgage or the related
borrower's operations at the Mortgaged Property;

            (xxviii) The information pertaining to the Mortgage Loans which is
set forth in the mortgage loan schedule attached as an exhibit to this Mortgage
Loan Purchase Agreement is complete and accurate in all material respects as of
the dates of the information set forth therein (or, if not set forth therein, as
of the Cut-Off Date);

            (xxix) With respect to any Mortgage Loan where all or a material
portion of the estate of the related borrower therein is a leasehold estate, and
the related Mortgage does not also encumber the related lessor's fee interest in
such Mortgaged Property, based upon the terms of the ground lease and any
estoppel received from the ground lessor, the Seller represents and warrants
that:

            (A) The ground lease or a memorandum regarding such ground lease has
      been duly recorded. The ground lease permits the interest of the lessee to
      be encumbered by the related Mortgage and does not restrict the use of the
      related Mortgaged Property by such lessee, its successors or assigns in a
      manner that would adversely affect the security provided by the related
      Mortgage. To the Seller's best knowledge, there has been no material
      change in the terms of the ground lease since its recordation, except by
      any written instruments which are included in the related mortgage file;

            (B) The lessor under such ground lease has agreed in a writing
      included in the related mortgage file that the ground lease may not be
      amended, modified, canceled or terminated without the prior written
      consent of the lender and that any such action without such consent is not
      binding on the lender, its successors or assigns;

            (C) The ground lease has an original term (or an original term plus
      one or more optional renewal terms, which, under all circumstances, may be
      exercised, and will be enforceable, by the lender) that extends not less
      than 20 years beyond the stated maturity of the related Mortgage Loan;

            (D) Based on the title insurance policy (or binding commitment
      therefor) obtained by the Seller, the ground lease is not subject to any
      liens or encumbrances superior to, or of equal priority with, the
      Mortgage, subject to Permitted Encumbrances and liens that encumber the
      ground lessor's fee interest;

            (E) The ground lease is assignable to the lender under the leasehold
      estate and its assigns without the consent of the lessor thereunder;

            (F) As of the Closing Date, the ground lease is in full force and
      effect, the Seller has no actual knowledge that any default beyond
      applicable notice and grace periods has occurred, and there is no existing
      condition which, but for the passage of time or giving of notice, would
      result in a default under the terms of the ground lease;

            (G) The ground lease or ancillary agreement between the lessor and
      the lessee requires the lessor to give notice of any default by the lessee
      to the lender;

            (H) A lender is permitted a reasonable opportunity (including, where
      necessary, sufficient time to gain possession of the interest of the
      lessee under the ground lease through legal proceedings, or to take other
      action so long as the lender is proceeding diligently) to cure any default
      under the ground lease which is curable after the receipt of notice of any
      default before the lessor may terminate the ground lease. All rights of
      the lender under the ground lease and the related Mortgage (insofar as it
      relates to the ground lease) may be exercised by or on behalf of the
      lender;

            (I) The ground lease does not impose any restrictions on subletting
      that would be viewed as commercially unreasonable by an institutional
      investor. The lessor is not permitted to disturb the possession, interest
      or quiet enjoyment of any subtenant of the lessee in the relevant portion
      of the Mortgaged Property subject to the ground lease for any reason, or
      in any manner, which would adversely affect the security provided by the
      related Mortgage;

            (J) Under the terms of the ground lease and the related Mortgage,
      any related insurance proceeds or condemnation award (other than in
      respect of a total or substantially total loss or taking) will be applied
      either to the repair or restoration of all or part of the related
      Mortgaged Property, with the lender or a trustee appointed by it having
      the right to hold and disburse such proceeds as repair or restoration
      progresses, or to the payment of the outstanding principal balance of the
      Mortgage Loan, together with any accrued interest, except that in the case
      of condemnation awards, the ground lessor may be entitled to a portion of
      such award;

            (K) Under the terms of the ground lease and the related Mortgage,
      any related insurance proceeds, or condemnation award in respect of a
      total or substantially total loss or taking of the related Mortgaged
      Property will be applied first to the payment of the outstanding principal
      balance of the Mortgage Loan, together with any accrued interest (except
      as provided by applicable law or in cases where a different allocation
      would not be viewed as commercially unreasonable by any institutional
      investor, taking into account the relative duration of the ground lease
      and the related Mortgage and the ratio of the market value of the related
      Mortgaged Property to the outstanding principal balance of such Mortgage
      Loan). Until the principal balance and accrued interest are paid in full,
      neither the lessee nor the lessor under the ground lease will have an
      option to terminate or modify the ground lease without the prior written
      consent of the lender as a result of any casualty or partial condemnation,
      except to provide for an abatement of the rent; and

            (L) Provided that the lender cures any defaults which are
      susceptible to being cured, the lessor has agreed to enter into a new
      lease upon termination of the ground lease for any reason, including
      rejection of the ground lease in a bankruptcy proceeding;

            (xxx) With respect to any Mortgage Loan where all or a material
portion of the estate of the related borrower therein is a leasehold estate, but
the related Mortgage also encumbers the related lessor's fee interest in such
Mortgaged Property: (a) such lien on the related fee interest is evidenced by
the related Mortgage, (b) such Mortgage does not by its terms provide that it
will be subordinated to the lien of any other mortgage or encumbrance upon such
fee interest, (c) upon the occurrence of a default under the terms of such
Mortgage by the related borrower, any right of the related lessor to receive
notice of, and to cure, such default granted to such lessor under any agreement
binding upon the Seller would not be considered commercially unreasonable in any
material respect by prudent commercial mortgage lenders, (d) the related lessor
has agreed in a writing included in the related mortgage file that the related
ground lease may not be amended or modified without the prior written consent of
the lender and that any such action without such consent is not binding on the
lender, its successors or assigns, and (e) the related ground lease is in full
force and effect, and the Seller has no actual knowledge that any default beyond
applicable notice and grace periods has occurred or that there is any existing
condition which, but for the passage of time or giving of notice, would result
in a default under the terms of such ground lease;

            (xxxi) With respect to Mortgage Loans that are cross-collateralized
or cross-defaulted, all other loans that are cross-collateralized by or
cross-defaulted with such Mortgage Loans are being transferred to the Depositor;

            (xxxii) Neither Seller nor any affiliate thereof has any obligation
to make any capital contribution to any borrower under a Mortgage Loan, other
than contributions made on or prior to the date hereof;

            (xxxiii) (1) The Mortgage Loan is directly secured by a Mortgage on
a commercial property or multifamily residential property, and (2) the fair
market value of such real property, as evidenced by an appraisal satisfying the
requirements of FIRREA conducted within 12 months of the origination of the
Mortgage Loan, was at least equal to 80% of the principal amount of the Mortgage
Loan (a) at origination (or if the Mortgage Loan has been modified in a manner
that constituted a deemed exchange under Section 1001 of the Code at a time when
the Mortgage Loan was not in default or default with respect thereto was not
reasonably foreseeable, the date of the last such modification) or (b) at the
date hereof; provided that the fair market value of the real property must first
be reduced by (A) the amount of any lien on the real property interest that is
senior to the Mortgage Loan and (B) a proportionate amount of any lien that is
in parity with the Mortgage Loan (unless such other lien secures a Mortgage Loan
that is cross-collateralized with such Mortgage Loan, in which event the
computation described in (a) and (b) shall be made on an aggregated basis);

            (xxxiv) There are no subordinate mortgages encumbering the related
Mortgaged Property, nor are there any preferred equity interests held by the
Seller or any mezzanine debt related to such Mortgaged Property, except as set
forth in the Prospectus Supplement, this Exhibit A or in the Exception Report to
this Mortgage Loan Purchase Agreement;

            (xxxv) The Mortgage Loan Documents executed in connection with each
Mortgage Loan having an original principal balance in excess of $10,000,000
require that the related borrower be a single-purpose entity (for this purpose,
"single-purpose entity" shall mean an entity, other than an individual, having
organizational documents which provide substantially to the effect that it is
formed or organized solely for the purpose of owning and operating one or more
Mortgaged Properties, is prohibited from engaging in any business unrelated to
such property and the related Mortgage Loan, does not have any assets other than
those related to its interest in the related Mortgaged Property or its
financing, or any indebtedness other than as permitted under the related
Mortgage Loan);

            (xxxvi) Each Mortgage Loan prohibits the related borrower from
mortgaging or otherwise encumbering the Mortgaged Property without the prior
written consent of the mortgagee or the satisfaction of debt service coverage or
similar criteria specified therein and, except in connection with trade debt and
equipment financings in the ordinary course of borrower's business, from
carrying any additional indebtedness, except, in each case, liens contested in
accordance with the terms of the Mortgage Loans;

            (xxxvii) Each borrower covenants in the Mortgage Loan documents that
it shall remain in material compliance with all material licenses, permits and
other legal requirements necessary and required to conduct its business;

            (xxxviii) Each Mortgaged Property (a) is located on or adjacent to a
dedicated road, or has access to an irrevocable easement permitting ingress and
egress, (b) is served by public utilities and services generally available in
the surrounding community or otherwise appropriate for the use in which the
Mortgaged Property is currently being utilized, and (c) constitutes one or more
separate tax parcels or is covered by an endorsement with respect to the matters
described in (a), (b) or (c) under the related title insurance policy (or the
binding commitment therefor);

            (xxxix) Based solely on a flood zone certification or a survey of
the related Mortgaged Property, if any portion of the improvements on the
Mortgaged Property is located in an area identified by the Federal Emergency
Management Agency or the Secretary of Housing and Urban Development as having
special flood hazards categorized as Zone "A" or Zone "V" and flood insurance is
available, the terms of the Mortgage Loan require the borrower to maintain flood
insurance, or at such borrower's failure to do so, authorizes the Lender to
maintain such insurance at the cost and expense of the borrower;

            (xl) To the knowledge of the Seller, with respect to each Mortgage
which is a deed of trust, a trustee, duly qualified under applicable law to
serve as such, currently so serves and is named in the deed of trust or has been
substituted in accordance with applicable law or may be substituted in
accordance with applicable law by the related mortgagee, and except in
connection with a trustee's sale after a default by the related borrower, no
fees are payable to such trustee;

            (xli) RESERVED.

            (xlii) Except as disclosed in the Exception Report to this Mortgage
Loan Purchase Agreement or the Prospectus Supplement, to the knowledge of the
Seller as of the date hereof, there was no pending action, suit or proceeding,
arbitration or governmental investigation against any borrower or Mortgaged
Property, an adverse outcome of which would materially and adversely affect such
borrower's ability to perform under the related Mortgage Loan;

            (xliii) No advance of funds has been made by the Seller to the
related borrower (other than mezzanine debt and the acquisition of preferred
equity interests by the Preferred Interest Holder, as disclosed in the
Prospectus Supplement), and no funds have, to the Seller's knowledge, been
received from any person other than, or on behalf of, the related borrower, for,
or on account of, payments due on the Mortgage Loan;

            (xliv) To the extent required under applicable law, as of the
Cut-off Date or as of the date that such entity held the Note, each holder of
the Note was authorized to transact and do business in the jurisdiction in which
each related Mortgaged Property is located, or the failure to be so authorized
did not materially and adversely affect the enforceability of such Mortgage
Loan;

            (xlv) All collateral for the Mortgage Loans is being transferred as
part of the Mortgage Loans;

            (xlvi) Except as disclosed in the Exception Report to this Mortgage
Loan Purchase Agreement or the Prospectus Supplement with respect to the Crossed
Loans and Multiple Property Loans, no Mortgage Loan requires the lender to
release any portion of the Mortgaged Property from the lien of the related
Mortgage except upon (a) payment in full or defeasance of the related Mortgage
Loan, (b) the satisfaction of certain legal and underwriting requirements, (c)
releases of unimproved out-parcels or (d) releases of portions of the Mortgaged
Property which will not have a material adverse effect on the value of the
collateral for the related Mortgage Loan;

            (xlvii) Except as provided in paragraphs (xxix) (J) and (K) above,
any insurance proceeds in respect of a casualty loss or taking will be applied
either to (a) the repair or restoration of all or part of the related Mortgaged
Property, with, in the case of all Mortgage Loans other than Credit Lease Loans
and with respect to all casualty losses or takings in excess of a specified
percentage of the related loan amount, the lender (or a trustee appointed by it)
having the right to hold and disburse such proceeds as the repair or restoration
progresses (except in any case where a provision entitling another party to hold
and disburse such proceeds would not be viewed as commercially unreasonable by a
prudent commercial mortgage lender) or (b) to the payment of the outstanding
principal balance of such Mortgage Loan together with any accrued interest
thereon;

            (xlviii) Each Form UCC-1 financing statement, if any, filed with
respect to personal property constituting a part of the related Mortgaged
Property and each Form UCC-2 or UCC-3 assignment, if any, of such financing
statement to the Seller was, and each Form UCC-3 assignment, if any, of such
financing statement in blank which the Trustee or its designee is authorized to
complete (but for the insertion of the name of the assignee and any related
filing information which is not yet available to the Seller) is, in suitable
form for filing in the filing office in which such financing statement was
filed;

            (xlix) To the Seller's knowledge, (a) each commercial lease covering
more than 10% (20% in the case of any Mortgage Loan having an original principal
balance less than $2,500,000) of the net leaseable area of the related Mortgaged
Property is in full force and effect and (b) there exists no default under any
such commercial lease either by the lessee thereunder or by the related borrower
that could give rise to the termination of such lease;

            (l) Based upon an opinion of counsel and/or other due diligence
considered reasonable by prudent commercial mortgage lenders, the improvements
located on or forming part of each Mortgaged Property comply with applicable
zoning laws and ordinances, or constitute a legal non-conforming use or
structure or, if any such improvement does not so comply, such non-compliance
does not materially and adversely affect the value of the related Mortgaged
Property. With respect to properties with a Stated Principal Balance of over
$10,000,000, if the related Mortgaged Property does not so comply, to the extent
the Seller is aware of such non-compliance, it has required the related Borrower
to obtain law and ordinance insurance coverage in amounts customarily required
by prudent commercial mortgage lenders;

            (li) Each Mortgage Loan constitutes a "qualified mortgage" within
the meaning of Section 860G(a)(3) of the Code (but without regard to the rule in
Treasury Regulation (as defined herein) Section 1.860G-2(f)(2) that treats a
defective obligation as a qualified mortgage or any substantially similar
successor provision) and all Prepayment Premiums and Yield Maintenance Charges
constitute "customary prepayment penalties" within the meaning of Treasury
Regulation Section 1.860G-1(b)(2);

            (lii) With respect to any Mortgage Loan that pursuant to the
Mortgage Loan Documents can be defeased, (i) the Mortgage Loan cannot be
defeased within two years after the Closing Date, (ii) the borrower can pledge
only United States government securities in an amount sufficient to make all
scheduled payments under the Mortgage Loan when due, (iii) the borrower is
required to provide independent certified public accountant's certification that
the collateral is sufficient to make such payments, (iv) the loan may be
required to be assumed by a single-purpose entity designated by the holder of
the Mortgage Loan, and (v) the borrower is required to provide an opinion of
counsel that the trustee has a perfected security interest in such collateral
prior to any other claim or interest;

            (liii) The Mortgage Loan Documents for each Mortgage Loan provide
that the related borrower thereunder shall be liable to the Seller for any
losses incurred by the Seller due to (i) the misapplication or misappropriation
of rents, insurance proceeds or condemnation awards, (ii) any willful act of
material waste, (iii) any breach of the environmental covenants contained in the
related Mortgage Loan Documents, and (iv) fraud;

            (liv) If such Mortgage Loan is an ARD Loan, it commenced amortizing
on its initial scheduled Due Date and provides that: (i) its Mortgage Rate will
increase by no more than two percentage points in connection with the passage of
its Anticipated Repayment Date and so long as the Mortgage Loan is an asset of
the Trust Fund; (ii) its Anticipated Repayment Date is not less than seven years
following the origination of such Mortgage Loan; (iii) no later than the related
Anticipated Repayment Date, if it has not previously done so, the related
borrower is required to enter into a "lockbox agreement" whereby all revenue
from the related Mortgaged Property shall be deposited directly into a
designated account controlled by the Servicer; and (iv) any cash flow from the
related Mortgaged Property that is applied to amortize such Mortgage Loan
following its Anticipated Repayment Date shall, to the extent such net cash flow
is in excess of the Monthly Payment payable therefrom, be net of budgeted and
discretionary (servicer approved) capital expenditures;

            (lv) Except as disclosed in the Prospectus Supplement, no Mortgage
Loan, and no group of Mortgage Loans made to the same borrower and to borrowers
that are affiliates, accounted for more than 5.0% of the aggregate of the Stated
Principal Balances of all of the Mortgage Loans and the mortgage loans sold to
the Depositor by PNC Bank, National Association ("PNC Bank") pursuant to that
certain Mortgage Loan Purchase Agreement dated as of August 1, 2001 between the
Depositor and PNC Bank, as of the Cut-Off Date; and

            (lvi) The Seller has delivered to the Trustee or a custodian
appointed thereby, with respect to each Mortgage Loan, in accordance with
Section 2 of the Mortgage Loan Purchase Agreement, a complete Mortgage File.

<PAGE>

                                    EXHIBIT B

                             AFFIDAVIT OF LOST NOTE

STATE OF NEW YORK       )
                        )  ss.:
COUNTY OF NEW YORK      )

                        , being duly sworn, deposes and says:

            1. that he is an  authorized  signatory  of  Column  Financial,
Inc. ("Column");

            2. that Column is the owner and holder of a mortgage loan in the
original principal amount of $____ secured by a mortgage (the "Mortgage") on the
premises known as _____________ located in _____________;

            3. (a) that Column , after having conducted a diligent investigation
of its records and files, has been unable to locate the following original note
and believes that said original note has been lost, misfiled, misplaced or
destroyed due to a clerical error:

            a note in the original sum of $_____________ made by _____________,
            to Column Financial, Inc., under date of _____________ (the "Note");

            4. that the Note is now owned and held by Column;

            5. that the Note has not been paid off, satisfied, assigned,
transferred, encumbered, endorsed, pledged, hypothecated, or otherwise disposed
of and that the original Note has been either lost, misfiled, misplaced or
destroyed;

            6. that no other person, firm, corporation or other entity has any
right, title, interest or claim in the Note except Column; and

            7. upon assignment of the Note by Column to Credit Suisse First
Boston Mortgage Securities Corp. (the "Depositor") and subsequent assignment by
the Depositor to the trustee for the benefit of the holders of the Credit Suisse
First Boston Mortgage Securities Corp. Commercial Mortgage Pass-Through
Certificates, Series 2001-CP4 (the "Trustee") (which assignment may, at the
discretion of the Depositor, be made directly by Column to the Trustee) Column
covenants and agrees (a) promptly to deliver to the Trustee the original Note if
it is subsequently found, and (b) to indemnify and hold harmless the Trustee and
its successors and assigns from and against any and all costs, expenses and
monetary losses arising as a result of Column's failure to deliver said original
Note to the Trustee.

                                       COLUMN FINANCIAL, INC.

                                       By:___________________
                                          Name:
                                          Title:

Sworn to before me this
day of August [__], 2001

<PAGE>

                                    EXHIBIT C

                                     FORM OF

                          ASSIGNMENT OF MORTGAGE(S) AND
                 ASSIGNMENT OF ASSIGNMENT OF LESSOR'S INTERESTS
                          IN LEASES, RENTS AND PROFITS

            KNOW ALL MEN BY THESE PRESENTS:

            THAT, as of _____________, 2001, Column Financial, Inc., a Delaware
corporation, whose address is 3414 Peachtree Road, N.E., Suite 1140, Atlanta,
Georgia 30326 ("ASSIGNOR") in consideration of ten and 00/100 ($10.00) dollars
and other good and valuable consideration, paid by Wells Fargo Bank Minnesota,
N.A., as trustee for Credit Suisse First Boston Mortgage Securities Corp.
Commercial Mortgage Pass-Through Certificates, Series 2001-CP4, whose address is
45 Broadway, New York, New York 10001 ("ASSIGNEE"), receipt of which is
acknowledged by ASSIGNOR, hereby sells, assigns, transfers, sets over and
conveys unto the ASSIGNEE certain mortgage(s) and assignments of leases, rents
and profits and other collateral documents as follows:

                See Schedule "A" attached hereto and incorporated
                            herein by this reference.

            TOGETHER with the note(s), debt(s) and claim(s) secured by said
mortgage(s) and the covenants contained in said mortgage(s), together with all
amendments, supplements and modifications thereto and all liens, financing
statements, guaranties and security interests securing the payment of such
notes, including, without limitation, any other documents recorded in the real
property records of the jurisdiction in which the real property covered by the
mortgage(s) is located with respect to such notes, and any other documents,
agreements, instruments or property relating to such loan(s) and all right,
title, interest, claims, demands, causes of action and judgments securing or
relating to such loan(s); TO HAVE AND TO HOLD the same unto the ASSIGNEE and to
the successors, legal representatives and assigns of the ASSIGNEE forever.

            THIS ASSIGNMENT is made without recourse or representation or
warranty of any kind or nature, express or implied except as expressly set forth
in that certain Mortgage Loan Purchase Agreement, dated as of August 1, 2001
between ASSIGNOR and Credit Suisse First Boston Mortgage Securities Corp.

<PAGE>

            IN WITNESS WHEREOF, the ASSIGNOR has duly executed this Assignment
the __ day of ________ 2001.

IN PRESENCE OF:

[corporate seal]

                                       By: ___________________________________
                                           Name:
                                           Title:

<PAGE>

STATE OF                )
                        )  ss.:
COUNTY OF               )

            On this _____________ day of _____________, 2001, before me the
undersigned, a NOTARY PUBLIC OF _____________, personally appeared , as ________
of Column Financial, Inc., a Delaware corporation, who, I am satisfied, was the
maker of the foregoing instrument and who then stated and acknowledged to me
that, as such officer and maker (1) he was authorized to execute the foregoing
instrument on behalf of said company and (2) he executed said instrument as the
act and deed of said company.

            IN TESTIMONY WHEREOF, I have hereunto set my hand and affixed my
official seal at my office in _____________ the day and year last above written.

                                        Signature_______________________________

                                        Print Name______________________________

                                        Residing at_____________________________

                                                   _____________________________

                                                   _____________________________

                                        A NOTARY PUBLIC OF______________________

[AFFIX SEAL]                        My Commission expires on____________________

<PAGE>

                             ASSIGNMENT OF MORTGAGE
                                       AND
                 ASSIGNMENT OF ASSIGNMENT OF LESSOR'S INTERESTS
                          IN LEASES, RENTS AND PROFITS

                             COLUMN FINANCIAL, INC.
                                       TO
                  WELLS FARGO BANK MINNESOTA, N.A.., AS TRUSTEE

                              RECORD AND RETURN TO:EXECUTION COPY

================================================================================

             CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                                   (Depositor)

                                       and

                         PNC BANK, NATIONAL ASSOCIATION
                                    (Seller)

                 -------------------------------------------

                        MORTGAGE LOAN PURCHASE AGREEMENT

                           Dated as of August 1, 2001

                 -------------------------------------------

================================================================================

<PAGE>

                                TABLE OF CONTENTS

                                                                            Page

Section 1.    Transactions on or Prior to the Closing Date..................
Section 2.    Closing Date Actions..........................................
Section 3.    Conveyance of Mortgage Loans..................................
Section 4.    Depositor's Conditions to Closing.............................
Section 5.    Seller's Conditions to Closing................................
Section 6.    Representations and Warranties of Seller......................
Section 7.    Obligations of Seller.........................................
Section 8.    Crossed Loans.................................................
Section 9.    Rating Agency Fees; Costs and Expenses Associated with a
               Defeasance...................................................
Section 10.   Representations and Warranties of Depositor...................
Section 11.   Survival of Certain Representations, Warranties and
               Covenants....................................................
Section 12.   [Reserved]....................................................
Section 13.   Expenses; Recording Costs.....................................
Section 14.   Notices.......................................................
Section 15.   Examination of Mortgage Files.................................
Section 16.   Successors....................................................
Section 17.   Governing Law.................................................
Section 18.   Severability..................................................
Section 19.   Further Assurances............................................
Section 20.   Counterparts..................................................
Section 21.   Treatment as Security Agreement...............................
Section 22.   Recordation of Agreement......................................

Schedule I    Schedule of Transaction Terms
Schedule II   Mortgage Loan Schedule
Schedule III  Mortgage Loans Constituting Mortgage Groups
Schedule IV   Mortgage Loans with Lost Mortgage Notes
Schedule V    Exceptions with Respect to Seller's Representations and Warranties

<PAGE>

Exhibit A     Representations and Warranties of Seller Regarding the Mortgage
              Loans
Exhibit B     Form of Lost Mortgage Note Affidavit
Exhibit C     Form of Assignment of Mortgage(s) and Assignment of Assignment of
              Lessor's Interests in Leases, Rents and Profits

<PAGE>

                        MORTGAGE LOAN PURCHASE AGREEMENT

            This Mortgage Loan Purchase Agreement (this "Agreement"), dated as
of August 1, 2001, is made by and between PNC BANK, NATIONAL ASSOCIATION, a
national banking association ("Seller"), and CREDIT SUISSE FIRST BOSTON MORTGAGE
SECURITIES CORP., a Delaware corporation (the "Depositor").

                                    RECITALS

            I. Capitalized terms used herein without definition have the
meanings ascribed to them in the Schedule of Transaction Terms attached hereto
as Schedule I, which is incorporated herein by this reference, or, if not
defined therein, in the Pooling and Servicing Agreement.

            II. On the Closing Date, and on the terms set forth herein, Seller
has agreed to sell to Depositor and Depositor has agreed to purchase from Seller
the Mortgage Loans identified on the schedule (the "Mortgage Loan Schedule")
annexed hereto as Schedule II. Depositor intends to deposit the Mortgage Loans
and other assets into the Trust Fund created pursuant to the Pooling and
Servicing Agreement and to cause the issuance of the Certificates.

                                    AGREEMENT

            NOW, THEREFORE, on the terms and conditions set forth below and for
good and valuable consideration, the receipt and adequacy of which is hereby
acknowledged, Depositor and Seller agree as follows:

            Section 1. Transactions on or Prior to the Closing Date. On or prior
to the Closing Date, Seller shall have delivered the Mortgage Files with respect
to each of the Mortgage Loans listed in the Mortgage Loan Schedule to Wells
Fargo Bank Minnesota, N.A. as trustee (the "Trustee"), against receipt by Seller
of a trust receipt, pursuant to an arrangement between Seller and the Trustee;
provided, however, that item (p) in the definition of Mortgage File (below)
shall be delivered to the Servicer for inclusion in the Servicer File (defined
below) with a copy delivered to the Trustee for inclusion in the Mortgage File.

            Section 2. Closing Date Actions. The sale of the Mortgage Loans
shall take place on the Closing Date, subject to and simultaneously with the
deposit of the Mortgage Loans into the Trust Fund, the issuance of the
Certificates and the sale of (a) the Offered Certificates by Depositor to the
Underwriters pursuant to the Underwriting Agreement and (b) the Private
Certificates by Depositor to the Initial Purchaser pursuant to the Certificate
Purchase Agreement. The closing shall take place at the offices of Cadwalader,
Wickersham & Taft, 100 Maiden Lane, New York, New York 10038, or such other
location as agreed upon between the parties hereto. On the Closing Date, the
following actions shall take place in sequential order on the terms set forth
herein:

      (i) Seller shall sell to Depositor, and Depositor shall purchase from
Seller, the Mortgage Loans pursuant to this Agreement for the Mortgage Loan
Purchase Price payable in accordance with instructions previously provided to
Depositor by Seller. The Mortgage Loan Purchase Price (as defined herein) shall
be paid by Depositor to Seller or at its direction by wire transfer in
immediately available funds to an account designated by Seller on or prior to
the Closing Date. The "Mortgage Loan Purchase Price" paid by Depositor shall be
equal to $240,565,205.64. In addition, for no consideration other than the
Mortgage Loan Purchase Price, the Seller shall acquire, or cause a nominee to
acquire, Seller's proportionate share of the residual Certificates under the
Pooling and Servicing Agreement.

      (ii) Pursuant to the terms of the Pooling and Servicing Agreement,
Depositor shall sell all of its right, title and interest in and to the Mortgage
Loans to the Trustee for the benefit of the Holders of the Certificates.

      (iii) Depositor shall sell to the Underwriters, and the Underwriters shall
purchase from Depositor, the Offered Certificates pursuant to the Underwriting
Agreement, and Depositor shall sell to the Initial Purchaser, and the Initial
Purchaser shall purchase from Depositor, the Private Certificates pursuant to
the Certificate Purchase Agreement.

      (iv) The Underwriters will offer the Offered Certificates for sale to the
public pursuant to the Prospectus and the Prospectus Supplement and the Initial
Purchaser will privately place certain classes of the Certificates pursuant to
the Offering Circular.

            Section 3. Conveyance of Mortgage Loans. On the Closing Date, Seller
shall sell, convey, assign and transfer on a servicing released basis, without
recourse except as provided herein, to Depositor, free and clear of any liens,
claims or other encumbrances, all of Seller's right, title and interest in, to
and under each of the Mortgage Loans identified on the Mortgage Loan Schedule
and all property of Seller described in Section 21(b) of this Agreement,
including, without limitation, (A) all scheduled payments of interest and
principal due on or with respect to the Mortgage Loans after the Cut-off Date
and (B) all other payments of interest, principal or prepayment premiums
received on or with respect to the Mortgage Loans after the Cut-off Date, other
than any such payments of interest or principal or prepayment premiums that were
due on or prior to the Cut-off Date. Each Mortgage File shall contain the
following documents:

            (a) the original Note, or with respect to those Mortgage Loans
listed in Schedule IV hereto, a "lost note affidavit" substantially in the form
of Exhibit B hereto and a true and complete copy of the Note, bearing, or
accompanied by, all prior and intervening endorsements or assignments showing a
complete chain of endorsement or assignment from the Mortgage Loan Originator
either in blank or to the Seller, and further endorsed (at the direction of the
Depositor given pursuant to the Mortgage Loan Purchase Agreement) by the Seller
on its face or by allonge attached thereto, without recourse, to the order of
the Trustee in the following form: "Pay to the order of Wells Fargo Bank
Minnesota, N.A., as trustee for the registered Holders of Credit Suisse First
Boston Mortgage Securities Corp., Commercial Mortgage Pass-Through Certificates,
Series 2001-CP4, without recourse, representation or warranty, express or
implied";

            (b) a duplicate original Mortgage or a counterpart thereof or, if
such Mortgage has been returned by the related recording office, (A) an
original, (B) a certified copy or (C) a copy thereof from the applicable
recording office and originals or counterparts (or originals or copies of
certified copies from the applicable recording office) of any assignments
thereof showing a complete chain of assignment from the Mortgage Loan Originator
to the Seller, in each case in the form submitted for recording or, if recorded,
with evidence of recording indicated thereon;

            (c) an original Assignment of Mortgage substantially in the form of
Exhibit C hereto, in recordable form, either in blank or from the Seller to
"Wells Fargo Bank Minnesota, N.A., as trustee for the registered Holders of
Credit Suisse First Boston Mortgage Securities Corp., Commercial Mortgage
Pass-Through Certificates, Series 2001-CP4";

            (d) an original, counterpart or copy of any related Assignment of
Leases (if such item is a document separate from the Mortgage) and the
originals, counterparts or copies of any assignments thereof showing a complete
chain of assignment from the Mortgage Loan Originator of the Loan to the Seller,
in each case in the form submitted for recording or, if recorded, with evidence
of recording thereon;

            (e) an original assignment of any related Assignment of Leases (if
such item is a document separate from the Mortgage), substantially in the form
of Exhibit C hereto in recordable form, either in blank or from the Seller to
"Wells Fargo Bank Minnesota, N.A., as trustee for the registered Holders of
Credit Suisse First Boston Mortgage Securities Corp., Commercial Mortgage
Pass-Through Certificates, Series 2001-CP4";

            (f) an original or true and complete copy of any related Security
Agreement (if such item is a document separate from the Mortgage) and the
originals or copies of any assignments thereof showing a complete chain of
assignment from the Mortgage Loan Originator to the Seller;

            (g) an original assignment of any related Security Agreement (if
such item is a document separate from the Mortgage), either in blank or from the
Seller (or the Mortgage Loan Originator) to "Wells Fargo Bank Minnesota, N.A.,
as trustee for the registered Holders of Credit Suisse First Boston Mortgage
Securities Corp., Commercial Mortgage Pass-Through Certificates, Series
2001-CP4," which assignment may be included as part of an omnibus assignment
covering other documents relating to the Mortgage Loan provided that such
omnibus assignment is effective under applicable law;

            (h) originals or copies of all (A) assumption agreements, (B)
modifications, (C) written assurance agreements and (D) substitution agreements,
together with any evidence of recording thereon, or in the form submitted for
recording, in those instances where the terms or provisions of the Mortgage,
Note or any related security document have been modified or the Mortgage Loan
has been assumed;

            (i) the original lender's title insurance policy or a copy thereof
(together with all endorsements or riders that were issued with or subsequent to
the issuance of such policy), or if the policy has not yet been issued, a
binding written commitment (which may be a pro forma or specimen title insurance
policy which has been accepted or approved in writing by the related title
insurance company) or interim binder that is marked as binding and countersigned
by the title company, insuring the priority of the Mortgage as a first lien on
the related Mortgaged Property, relating to such Mortgage Loan;

            (j) the original or a counterpart of any guaranty of the obligations
of the Borrower under the Mortgage Loan;

            (k) certified or other copies of all UCC Financing Statements and
continuation statements which show the filing or recording thereof or copies
thereof in the form submitted for filing or recording sufficient to perfect (and
maintain the perfection of) the security interest held by the Mortgage Loan
Originator (and each assignee prior to the Trustee) in and to the personalty of
the Borrower at the Mortgaged Property, and original UCC assignments in a form
suitable for filing or recording sufficient to transfer such security interest
to the Trustee;

            (l) the original or copy of the power of attorney (with evidence of
recording thereon) granted by the Borrower if the Mortgage, Note or other
document or instrument referred to above was not signed by the Borrower;

            (m) with respect to any debt of a Borrower permitted under the
related Mortgage Loan, an original or copy of a subordination agreement,
standstill agreement or other intercreditor agreement relating to such other
debt, if any, including any mezzanine loan documents or preferred equity
documents;

            (n) if any related Lock-Box Agreement or Cash Collateral Agreement
is separate from the Mortgage or Loan Agreement, a copy thereof; with respect to
the Cash Collateral Accounts and Lock-Box Accounts, if any, a copy of the UCC-1
financing statements, if any, submitted for filing with respect to the Seller's
security interest in the Cash Collateral Accounts and Lock-Box Accounts and all
funds contained therein (and UCC-2 or UCC-3 financing statement assignments
assigning such security interest to the Trustee on behalf of the
Certificateholders);

            (o) an original or counterpart of the Loan Agreement (if separate
from the Mortgage);

            (p) the originals of letters of credit, if any, relating to the
Mortgage Loans, and amendments thereto which entitles the Trust to draw thereon;

            (q) the original environmental indemnity agreement, if any, related
to the Mortgage Loan;

            (r) any related environmental insurance policies;

            (s) the original ground lease, if any, or a certified copy thereof;
and

            (t) any additional documents required to be added to the Mortgage
File pursuant to the Pooling and Servicing Agreement.

            Notwithstanding the foregoing, in the event that, in connection with
any Mortgage Loan, Seller cannot deliver, or cause to be delivered, an original,
counterpart or certified copy of any of the documents required to be delivered
pursuant to clauses (b), (d), (h), (k) (with respect to UCC financing statements
and assignments recorded or filed other than in accordance with the transfer
contemplated by this Agreement), (l) and (n) above with evidence of recording or
filing thereon on the Closing Date, solely because of a delay caused by the
public recording or filing office where such document or instrument has been
delivered for recordation, or filing, the Seller shall deliver, or cause to be
delivered, to the Trustee a duplicate original or true copy of such document
certified by the applicable public recording or filing office, the applicable
title insurance company or the Seller to be a true and complete duplicate
original or copy of the original thereof submitted for recording or filing.

            Notwithstanding the foregoing, in the event that, in connection with
any Mortgage Loan, the Seller cannot deliver, or cause to be delivered, an
original, counterpart or certified copy of any of the documents required to be
delivered pursuant to clauses (b), (d), (h), (k) (with respect to UCC financing
statements and assignments recorded or filed other than in accordance with the
transfer contemplated by this Agreement), (l) and (n) above with evidence of
recording or filing thereon, for any other reason, including without limitation,
that such non-delivered document has been lost, the delivery requirements of
this Agreement shall be deemed to have been satisfied and such non-delivered
document shall be deemed to have been included in the related Mortgage File if a
photocopy of such non-delivered document (with evidence of recording or filing
thereon and certified by the appropriate recording or filing office to be a true
and complete copy of the original thereof as filed or recorded) is delivered to
the Trustee on or before the Closing Date.

            Notwithstanding the foregoing, in the event that Seller cannot
deliver to the Trustee any UCC-2 or UCC-3 assignment with the filing information
of the UCC-1 financing statement being assigned, solely because such UCC-1
financing statement has not been returned by the public filing office where such
UCC-1 financing statement has been delivered for filing, Seller shall deliver or
cause to be delivered to the Trustee a photocopy of such UCC-2 or UCC-3
assignment with the filing information left blank. The Seller, promptly upon
receipt of the applicable filing information of the UCC-1 financing statement
being so assigned, shall deliver or cause to be delivered to the Trustee the
original UCC-2 or UCC-3 assignment with all appropriate filing information set
forth thereon.

            On or prior to the Closing Date, the Seller shall deliver the
Servicer Files with respect to each of the Mortgage Loans to the Servicer under
the Pooling and Servicing Agreement on behalf of the Trustee in trust for the
benefit of the Certificateholders. Each such Servicer File shall contain all
documents and records in the Seller's possession relating to the applicable
Mortgage Loans (including reserve and escrow agreements, cash management
agreements, lockbox agreements, financial statements and any other information
provided by the respective Borrower from time to time, but excluding documents
prepared by the Seller or any of its Affiliates solely for internal
communication) that are not required to be a part of a Mortgage File in
accordance with the definition thereof, together with copies of all instruments
and documents which are required to be a part of the related Mortgage File in
accordance with the definition thereof.

            For purposes of this Section 3, and notwithstanding any contrary
provision hereof or of the definition of "Mortgage File", if there exists with
respect to any group of Crossed Loans only one original or certified copy of any
document or instrument described in the definition of "Mortgage File" which
pertains to all of the Crossed Loans in such group of Crossed Loans, the
inclusion of the original or certified copy of such document or instrument in
the Mortgage File for any of such Crossed Loans and the inclusion of a copy of
such original or certified copy in each of the Mortgage Files for the other
Crossed Loans in such group of Crossed Loans, shall be deemed the inclusion of
such original or certified copy, as the case may be, in the Mortgage File for
each such Crossed Loan.

            The Trustee, as assignee or transferee of Depositor, shall be
entitled to all scheduled principal payments due after the Cut-off Date, all
other payments of principal due and collected after the Cut-off Date, and all
payments of interest on the Mortgage Loans, minus that portion of any such
payment which is allocable to the period on or prior to the Cut-off Date. All
scheduled payments of principal due on or before the Cut-off Date and collected
after the Cut-off Date, together with the accompanying interest payments, shall
belong to Seller.

            Upon the sale of the Mortgage Loans from Seller to Depositor
pursuant hereto, the ownership of each Mortgage Note, the Mortgage and the
contents of the related Mortgage File shall be vested in Depositor and the
ownership of all records and documents with respect to the related Mortgage Loan
prepared by or which come into the possession of Seller as seller of the
Mortgage Loans hereunder, exclusive in each case of documents prepared by Seller
or any of its affiliates solely for internal uses, shall immediately vest in
Depositor. All Monthly Payments, Principal Prepayments and other amounts
received by Seller and not otherwise belonging to Seller pursuant to this
Agreement shall be sent by Seller within three (3) Business Days of Seller's
receipt thereof to the Servicer via wire transfer for deposit by the Servicer
into the Collection Account.

            Section 4. Depositor's Conditions to Closing. The obligations of
Depositor to purchase the Mortgage Loans and pay the Mortgage Loan Purchase
Price at the Closing Date under the terms of this Agreement are subject to the
satisfaction of each of the following conditions at or before the Closing:

            (a) Each of the obligations of the Seller required to be performed
by it on or prior to the Closing Date pursuant to the terms of this Agreement
shall have been duly performed and complied with in all material respects; all
of the representations and warranties of Seller under this Agreement shall be
true and correct in all material respects as of the Closing Date; and no event
shall have occurred with respect to the Seller or any of the Mortgage Loans and
related Mortgage Files which, with notice or the passage of time, would
constitute a material default under this Agreement; and Depositor shall have
received certificates to the foregoing effect signed by authorized officers of
Seller.

            (b) Depositor, or if directed by Depositor, the Trustee or the
Depositor's attorneys, shall have received in escrow, all of the following
closing documents, in such forms as are agreed upon and reasonably acceptable to
the Depositor and the Seller, duly executed by all signatories other than
Depositor, as required pursuant to the respective terms thereof:

            (i) the Mortgage Files and the Servicer Files, which shall have been
      delivered to and held by the Trustee and the Servicer, respectively, on
      behalf of Seller;

            (ii) the Mortgage Loan Schedule;

            (iii) the certificate of the Seller confirming its representations
      and warranties set forth in Section 6 as of the Closing Date;

            (iv) an opinion or opinions of Seller's counsel, dated the Closing
      Date, in form acceptable to the Depositor as to various corporate matters
      and such other matters as shall be reasonably required by the Depositor.

            Such opinion may express its reliance as to factual matters on,
among other things specified in such opinion, the representations and warranties
made herein, and on certificates or other documents furnished by officers of
Seller.

            In rendering the opinions expressed above, such counsel may limit
such opinions to matters governed by the laws of the State of New York and the
United States and shall not be required to express any opinion with respect to
the registration or qualification of the Certificates under any applicable state
or federal securities laws.

            Such counsel shall state that, although such counsel has not
specifically considered the possible applicability to Seller of any other laws,
regulations, judgments, orders or decrees, no facts have been disclosed to such
counsel that cause such counsel to conclude that any other consent, approval or
action is required;

            (v) such other certificates of Seller's officers or others and such
      other documents to evidence fulfillment of the conditions set forth in
      this Agreement as Depositor or its counsel may reasonably request.

            (vi) all other information, documents, certificates, or letters with
      respect to the Mortgage Loans or the Sellers and their Affiliates as are
      reasonably requested by the Depositor in order for the Depositor to
      perform any of it obligations or satisfy any of the conditions on its part
      to be performed or satisfied pursuant to any sale of Mortgage Loans by the
      Depositor as contemplated herein;

            (c) The Seller shall have performed or complied with all other terms
and conditions of this Agreement which it is required to perform or comply with
at or before the Closing and shall have the ability to perform or comply with
all duties, obligations, provisions and terms which it is required to perform or
comply with after the Closing.

            (d) The Seller shall have delivered to the Trustee, on or before the
Closing Date, five limited powers of attorney in favor of the Trustee and
Special Servicer empowering the Trustee and, in the event of the failure or
incapacity of the Trustee, the Special Servicer, to record, at the expense of
the Seller, any Mortgage Loan Documents required to be recorded and any
intervening assignments with evidence of recording thereon that are required to
be included in the Mortgage Files. The Seller shall reasonably cooperate with
the Trustee and the Special Servicer in connection with any additional powers or
revisions thereto that are requested by such parties.

            Section 5. Seller's Conditions to Closing. The obligations of Seller
under this Agreement shall be subject to the satisfaction, on the Closing Date,
of the following conditions:

            (a) Each of the obligations of Depositor required to be performed by
it on or prior to the Closing Date pursuant to the terms of this Agreement shall
have been duly performed and complied with in all material respects; and all of
the representations and warranties of Depositor under this Agreement shall be
true and correct in all material respects as of the Closing Date; and no event
shall have occurred with respect to Depositor which, with notice or the passage
of time, would constitute a material default under this Agreement, and Seller
shall have received certificates to that effect signed by authorized officers of
Depositor.

            (b) Seller shall have received all of the following closing
documents, in such forms as are agreed upon and reasonably acceptable to Seller
and Depositor, duly executed by all signatories other than Seller, as required
pursuant to the respective terms thereof:

                  (A) an officer's certificate of Depositor, dated as of the
            Closing Date, with the resolutions of Depositor authorizing the
            transactions set forth therein, together with copies of the charter,
            by-laws and certificate of good standing dated as of a recent date
            of Depositor;

                  (B) such other certificates of its officers or others, such
            opinions of Depositor's counsel and such other documents required to
            evidence fulfillment of the conditions set forth in this Agreement
            as Seller or its counsel may reasonably request; and

            (c) The Depositor shall have performed or complied with all other
terms and conditions of this Agreement which it is required to perform or comply
with at or before the Closing and shall have the ability to perform or comply
with all duties, obligations, provisions and terms which it is required to
perform or comply with after Closing.

            Section 6. Representations and Warranties of Seller.

            (a) Seller represents and warrants to Depositor as of the date
hereof, as follows:

            (i) Seller is a national banking association duly organized, validly
      existing and in good standing under the laws of the United States of
      America and is in compliance in all material respects with all applicable
      statutes and regulations of regulatory bodies or agencies having
      jurisdiction over it to the extent necessary to insure the enforceability
      of each Mortgage Loan and the assignment thereof to the Depositor as
      herein provided and to perform its duties and obligations under this
      Agreement.

            (ii) Seller has the full power, authority and legal right to hold,
      transfer and covey the Mortgage Loans owned by it and to execute and
      deliver this Agreement (and all agreements and documents executed and
      delivered by Seller in connection herewith) and to perform all
      transactions of Seller contemplated by this Agreement (and all agreements
      and documents executed and delivered by Seller in connection herewith).
      Seller has duly authorized the execution, delivery and performance of this
      Agreement (and all agreements and documents executed and delivered by
      Seller in connection herewith), and has duly executed and delivered this
      Agreement (and all agreements and documents executed and delivered by
      Seller in connection herewith). This Agreement (and each agreement and
      document executed and delivered by Seller in connection herewith),
      assuming due authorization, execution and delivery thereof by each other
      party thereto, constitutes the legal, valid and binding obligation of
      Seller enforceable in accordance with its terms, except as such
      enforcement may be limited by bankruptcy, insolvency, reorganization,
      receivership, moratorium or other laws relating to or affecting the rights
      of creditors generally, by general principles of equity (regardless of
      whether such enforcement is considered in a proceeding in equity or at
      law) and by considerations of public policy.

            (iii) Neither the execution and delivery of this Agreement, nor the
      fulfillment of or compliance with the terms and conditions of this
      Agreement by Seller, will (a) conflict with or result in a breach of any
      of the terms, conditions or provisions of Seller's articles of
      association, as amended, or other organizational documents; (b) conflict
      with, result in a breach of, or constitute a default or result in an
      acceleration under, any agreement or instrument to which Seller is now a
      party or by which it (or any of its properties) is bound if compliance
      therewith is necessary (1) to ensure the enforceability of this Agreement
      or (2) for Seller to perform its duties and obligations under this
      Agreement (or any agreement or document executed and delivered by Seller
      in connection herewith); (c) conflict with or result in a breach of any
      legal restriction if compliance therewith is necessary (1) to ensure the
      enforceability of this Agreement or (2) for Seller to perform its duties
      and obligations under this Agreement (or any agreement or document
      executed and delivered by Seller in connection herewith); (d) result in
      the violation of any law, rule, regulation, order, judgment or decree to
      which Seller or its property is subject if compliance therewith is
      necessary (1) to ensure the enforceability of this Agreement or (2) for
      Seller to perform its duties and obligations under this Agreement (or any
      agreement or document executed and delivered by Seller in connection
      herewith); or (e) result in the creation or imposition of any lien, charge
      or encumbrance that would have a material adverse effect upon Seller's
      ability to perform its duties and obligations under this Agreement (or any
      agreement or document executed and delivered by Seller in connection
      herewith), or materially impair the ability of the Depositor to realize on
      the Mortgage Loans owned by Seller.

            (iv) Seller is solvent and the sale of Mortgage Loans (1) will not
      cause Seller to become insolvent and (2) is not intended by Seller to
      hinder, delay or defraud any of its creditors.

            (v) No consent, approval, authorization or order of, or registration
      or filing with, or notice to, any court or governmental agency or body
      having jurisdiction or regulatory authority over Seller is required for
      (a) Seller's execution and delivery of this Agreement (and each agreement
      and document executed and delivered by Seller in connection herewith), (b)
      Seller's transfer and assignment of the Mortgage Loans owned by it, or (c)
      the consummation by Seller of the transactions contemplated by this
      Agreement (and each agreement and document executed and delivered by
      Seller in connection herewith) or, to the extent so required, such
      consent, approval, authorization, order, registration, filing or notice
      has been obtained, made or given (as applicable), except that Seller may
      not be duly qualified to transact business as a foreign corporation or
      licensed in one or more states if such qualification or licensing is not
      necessary to ensure the enforceability of this Agreement (or any agreement
      or document executed and delivered by Seller in connection herewith).

            (vi) The consideration received by Seller upon the sale of the
      Mortgage Loans owned by it constitutes fair consideration and reasonably
      equivalent value for such Mortgage Loans.

            (vii) Seller does not believe, nor does it have any reason or cause
      to believe, that it cannot perform each and every covenant of Seller
      contained in this Agreement (or any agreement or document executed and
      delivered by Seller in connection herewith).

            (viii) There are no actions, suits proceedings pending or to
      Seller's knowledge threatened in writing against Seller which are
      reasonably likely to draw into question the validity of this Agreement (or
      any agreement or document executed and delivered by Seller in connection
      herewith) or which, either in any one instance or in the aggregate, are
      reasonably likely to materially impair the ability of Seller to perform
      its duties and obligations under this Agreement (or any agreement or
      document executed and delivered by Seller in connection herewith).

            (ix) Seller's performance of its duties and obligations under this
      Agreement (and each agreement or document executed and delivered by Seller
      in connection herewith) is in the ordinary course of business of Seller
      and Seller's transfer, assignment and conveyance of the Mortgage Loans
      owned by it pursuant to this Agreement are not subject to the bulk
      transfer or an similar statutory provisions in effect in any applicable
      jurisdiction.

            (x) Seller has not dealt with any Person that may be entitled, by
      reason of any act or omission of Seller, to any commission or compensation
      in connection with the sale of the Mortgage Loans owned by it to the
      Depositor hereunder except for the reimbursement of expenses as described
      herein or otherwise in connection with the transactions described in
      Section 2 and the commissions or compensation owed to the Underwriters or
      the Initial Purchasers.

            (xi) Seller is not in default or breach of any agreement or
      instrument to which Seller is now a party or by which it (or any of its
      properties) is bound which breach or default would materially and
      adversely affect the ability of Seller to perform its obligations under
      this Agreement.

            (xii) Except as set forth on Schedule V hereto, the representations
      and warranties contained in Exhibit A hereto are true and correct in all
      material respects as of the date hereof.

            Section 7. Obligations of Seller. Each of the representations and
warranties contained in or required to be made by Seller pursuant to Section 6
of this Agreement shall survive the sale of the Mortgage Loans and shall
continue in full force and effect, notwithstanding any restrictive or qualified
endorsement on the Notes and notwithstanding subsequent termination of this
Agreement or the Pooling and Servicing Agreement. The representations and
warranties contained in or required to be made by Seller pursuant to Section 6
of this Agreement shall not be impaired by any review or examination of the
Mortgage Files or other documents evidencing or relating to the Mortgage Loans
or any failure on the part of Depositor to review or examine such documents and
shall inure to the benefit of any initial transferee of the Mortgage Loans from
Depositor including, without limitation, the Trustee for the benefit of the
Holders of the Certificates, notwithstanding (1) any restrictive or qualified
endorsement on any Note, Assignment of Mortgage or reassignment of Assignment of
Leases or (2) any termination of this Agreement prior to the Closing.

            If any Certificateholder, the Servicer, the Special Servicer or the
Trustee discovers or receives notice: of a breach of any of the representations
or warranties made by the Seller with respect to the Mortgage Loans, as of the
date hereof in Section 6(a)(xii) or as of the Closing Date pursuant to Section
4(b)(iii) (a "Breach"); or that (a) any document required to be included in the
Mortgage File related to any Mortgage Loan is not in the Trustee's possession
within the time period required herein or (b) such document has not been
properly executed or is otherwise defective on its face (each, a "Defect" in the
related Mortgage File), such party shall give notice to the Servicer, the
Special Servicer, the Trustee and the Rating Agencies. If the Servicer or the
Special Servicer determines that such Breach or Defect materially and adversely
affects the value of any Mortgage Loan or the interests of the
Certificateholders therein, it shall give prompt written notice of such Breach
or Defect to the Depositor, the Trustee, the Servicer, the Special Servicer and
the Sellers and shall request that the Seller not later than the earlier of 90
days from the receipt by the Seller of such notice or discovery by the Seller of
such Breach or Defect (subject to the second succeeding paragraph, the "Initial
Resolution Period"), (i) cure such Breach or Defect in all material respects;
(ii) repurchase the affected Mortgage Loan at the applicable Purchase Price (as
defined in the Pooling and Servicing Agreement) or (iii) substitute one or more
Qualified Substitute Mortgage Loans (as defined in the Pooling and Servicing
Agreement) for such affected Mortgage Loan (provided that in no event shall any
substitution occur later than the second anniversary of the Closing Date) and
pay the Servicer for deposit into the Collection Account any Substitution
Shortfall Amount (as defined in the Pooling and Servicing Agreement) in
connection therewith; provided, however, that if (i) such material Breach or
material Defect is capable of being cured but not within the Initial Resolution
Period, (ii) such material Breach or material Defect does not cause the related
Mortgage Loan not to be a "qualified mortgage" (within the meaning of Section
860G(a)(3) of the Code) (iii) the Seller has commenced and is diligently
proceeding with the cure of such material Breach or material Defect within the
Initial Resolution Period and (iv) the Seller has delivered to the Rating
Agencies and the Trustee an Officer's Certificate that describes the reasons
that the cure was not effected within the Initial Resolution Period and the
actions that it proposes to take to effect the cure and that states that it
anticipates the cure will be effected within the additional 90-day period, then
the Seller shall have an additional 90 days to cure such material Defect or
material Breach. With respect to any substitution of one or more Qualified
Substitute Mortgage Loans for a Mortgage Loan hereunder, (A) no such
substitution may be made in any calendar month after the Determination Date for
such month; (B) scheduled payments of principal and interest due with respect to
the Qualified Substitute Mortgage Loan(s) after the related date of substitution
shall be part of the Trust Fund; and (C) scheduled payments of principal and
interest due with respect to such Qualified Substitute Mortgage Loan(s) on or
prior to the related date of substitution shall not be part of the Trust Fund,
and the Seller shall be entitled to receive such payments promptly following
receipt by the Servicer or Special Servicer, as applicable, under the Pooling
and Servicing Agreement.

            Any of the following will cause a document in the Mortgage File to
be deemed to have a "Defect" and to be conclusively presumed to materially and
adversely affect the interests of Certificateholders in a Mortgage Loan and to
be deemed to materially and adversely affect the interest of the
Certificateholders in and the value of a Mortgage Loan: (a) the absence from the
Mortgage File of the original signed Note, unless the Mortgage File contains a
signed lost note affidavit and indemnity that appears to be regular on its face;
(b) the absence from the Mortgage File of the original signed Mortgage that
appears to be regular on its face, unless there is included in the Mortgage File
a certified copy of the Mortgage as recorded or as sent for recordation,
together with a certificate stating that the original signed Mortgage was sent
for recordation; (c) the absence from the Mortgage File of the item called for
by paragraph (ix) of the definition of Mortgage File; (d) the absence from the
Mortgage File of any intervening assignments required to create a complete chain
of assignment to the Trustee on behalf of the Trust, unless there is included in
the Mortgage File a certified copy of the intervening assignment and a
certificate stating that the original intervening assignments were sent for
recordation; or (e) the absence from the Mortgage File of any required original
letter of credit.

            Any Defect or Breach which causes any Mortgage Loan not to be a
"qualified mortgage" (within the meaning of Section 860G(a)(3) of the Code)
shall be deemed to materially and adversely affect the interest of
Certificateholders therein and the Initial Resolution Period for the affected
Mortgage Loan shall be 90 days following the earlier of the Seller's receipt of
notice pursuant to this Section 7 or its discovery of such Defect or Breach
(which period shall not be subject to extension).

            If the Seller does not, as required by this Section 7, correct or
cure a material Breach or a material Defect in all material respects within the
applicable Initial Resolution Period (as extended pursuant to this Section 7),
or if such Breach or Defect is not capable of being so corrected or cured with
such period, then the Seller shall purchase or substitute for the affected
Mortgage Loan as provided in this Section 7. If (i) any Mortgage Loan is
required to be repurchased or substituted for as provided above, (ii) such
Mortgage Loan is a Crossed Loan that is a part of a Mortgage Group (as defined
below) and (iii) the applicable Breach or Defect does not constitute a Breach or
Defect, as the case may be, as to any other Crossed Loan in such Mortgage Group
(without regard to this paragraph), then the applicable Breach or Defect, as the
case may be, will be deemed to constitute a Breach or Defect, as the case may
be, as to any other Crossed Loan in the Mortgage Group for purposes of the above
provisions, and the Seller will be required to repurchase or substitute for such
other Crossed Loan(s) in the related Mortgage Group in accordance with the
provisions of this Section 7 unless such other Crossed Loans satisfy the Crossed
Loan Repurchase Criteria (as defined in the Pooling and Servicing Agreement). In
the event that one or more of such other Crossed Loans satisfy the Crossed Loan
Repurchase Criteria, the Seller may elect either to repurchase or substitute for
only the affected Crossed Loan as to which the related Breach or Defect exists
or to repurchase or substitute for all of the Crossed Loans in the related
Mortgage Group. The Seller shall be responsible for the cost of any Appraisal
required to be obtained by the Servicer to determine if the Crossed Loan
Repurchase Criteria have been satisfied, so long as the scope and cost of such
Appraisal has been approved by the Seller (such approval not to be unreasonably
withheld). For purposes of this paragraph, a "Mortgage Group" is any group of
Mortgage Loans identified as a Mortgage Group on Schedule III to this Agreement.

            Notwithstanding the foregoing, if there is a material Breach or
material Defect with respect to one or more Mortgaged Properties (but not all of
the Mortgaged Properties) with respect to a Mortgage Loan, the Seller will not
be obligated to repurchase or substitute for the Mortgage Loan if the affected
Mortgaged Property may be released pursuant to the terms of any partial release
provisions in the related Mortgage Loan Documents and the remaining Mortgaged
Property(ies) satisfy the requirements, if any, set forth in the Mortgage Loan
Documents and the Seller provides an opinion of counsel to the effect that such
partial release would not cause an Adverse REMIC Event (as defined in the
Pooling and Servicing Agreement) to occur and the Seller pays (or causes to be
paid) the applicable release price required under the Mortgage Loan Documents.

            The Purchase Price or Substitution Shortfall Amount for any
repurchased or substituted Mortgage Loan shall be payable to the Depositor or,
subsequent to the assignment of the Mortgage Loans to the Trustee, the Trustee
as its assignee, by wire transfer of immediately available funds to the account
designated by the Depositor or the Trustee, as the case may be, and the
Depositor or the Trustee, as the case may be, upon receipt of such funds, shall
promptly release the related Mortgage File and Servicer File or cause them to be
released, to Seller and shall execute and deliver such instruments of transfer
or assignment as shall be necessary to vest in the Seller the legal and
beneficial ownership of such Mortgage Loan (including any property acquired in
respect thereof or proceeds of any insurance policy with respect thereto) and
the related Mortgage Loan Documents.

            It is understood and agreed that the obligations of the Seller set
forth in this Section 7 to cure, substitute for or repurchase a Mortgage Loan
constitute the sole remedies available to the Depositor and its successors and
assigns respecting any Breach or Defect affecting such Mortgage Loan.

            Section 8. Crossed Loans. With respect to any Crossed Loan conveyed
hereunder, to the extent that the Seller repurchases or substitutes for an
affected Crossed Loan in the manner prescribed above while the Trustee continues
to hold any related Crossed Loans, the Seller and the Depositor (on behalf of
its successors and assigns) agree to forbear from enforcing any remedies against
the other's Primary Collateral, but each is permitted to exercise remedies
against the Primary Collateral securing its respective affected Crossed Loans,
including, with respect to the Trustee, the Primary Collateral securing Mortgage
Loans still held by the Trustee, so long as such exercise does not impair the
ability of the other party to exercise its remedies against its Primary
Collateral. If the exercise of remedies by one party would impair the ability of
the other party to exercise its remedies with respect to the Primary Collateral
securing the Crossed Loans held by such party, then both parties agree to
forbear from exercising such remedies until the Mortgage Loan Documents
evidencing and securing the relevant Mortgage Loans can be modified in a manner
that complies with this Agreement to remove the threat of impairment as a result
of the exercise of remedies. Any reserve or other cash collateral or letters of
credit securing the Crossed Loans shall be allocated between such Mortgage Loans
in accordance with the Mortgage Loan Documents, or otherwise on a pro rata basis
based upon their outstanding Stated Principal Balances. All other terms of the
Mortgage Loans shall remain in full force and effect, without any modification
thereof.

            Section 9. Rating Agency Fees; Costs and Expenses Associated with a
Defeasance. The Seller shall pay all Rating Agency fees associated with an
assumption of a Mortgage Loan to the extent such fees have not been paid by the
related Borrower and such Borrower is not required to pay them under the terms
of the related Mortgage Loan Documents in effect on or before the Closing Date.
The Seller shall pay all reasonable costs and expenses associated with a
defeasance of a Mortgage Loan to the extent such costs and expenses have not
been paid by the related Borrower and such Borrower is not required to pay them
under the terms of the related Mortgage Loan Documents in effect on or before
the Closing Date.

            Section 10. Representations and Warranties of Depositor. Depositor
hereby represents and warrants to Seller as of the date hereof, as follows:

            (a) Depositor is duly organized and is validly existing as a
corporation in good standing under the laws of the State of Delaware, with full
corporate power and authority to own its assets and conduct its business as it
is conducted, and is duly qualified as a foreign corporation in good standing in
all jurisdictions in which the ownership or lease of its property or the conduct
of its business requires such qualification (except where the failure to qualify
would not have a materially adverse effect on the consummation of any
transactions contemplated by this Agreement).

            (b) The execution and delivery by Depositor of this Agreement and
the performance of Depositor's obligations hereunder are within the corporate
power of Depositor and have been duly authorized by Depositor and neither the
execution and delivery by Depositor of this Agreement nor the compliance by
Depositor with the provisions hereof, nor the consummation by Depositor of the
transactions contemplated by this Agreement, will (i) conflict with or result in
a breach of, or constitute a default under, the certificate of incorporation or
by-laws of Depositor or, after giving effect to the consents or taking of the
actions contemplated by clause (ii) of this paragraph (b), any of the provisions
of any law, governmental rule, regulation, judgment, decree or order binding on
Depositor or its properties, or any of the provisions of any material indenture
or mortgage or any other material contract or other instrument to which
Depositor is a party or by which it is bound or result in the creation or
imposition of any lien, charge or encumbrance upon any of its properties
pursuant to the terms of any such indenture, mortgage, contract or other
instrument or (ii) require the consent of or notice to, or any filing with any
person, entity or governmental body, which has not been obtained or made by
Depositor, except where, in any of the instances contemplated by clause (i)
above or this clause (ii), the failure to do so will not have a material and
adverse effect on the consummation of any transactions contemplated by this
Agreement.

            (c) This Agreement has been duly executed and delivered by Depositor
and this Agreement constitutes a legal, valid and binding instrument,
enforceable against Depositor in accordance with its terms, subject, as to the
enforcement of remedies, to applicable bankruptcy, reorganization, insolvency,
moratorium and other laws affecting the rights of creditors generally and to
general principles of equity and the discretion of the court (regardless of
whether enforcement of such remedies is considered in a proceeding in equity or
at law) and, as to rights of indemnification hereunder, subject to limitations
of public policy under applicable securities laws.

            (d) There is no litigation, charge, investigation, action, suit or
proceeding by or before any court, regulatory authority or governmental agency
or body pending or, to the knowledge of Depositor, threatened against Depositor
the outcome of which could be reasonably expected to materially and adversely
affect the consummation of any transactions contemplated by this Agreement.

            Section 11. Survival of Certain Representations, Warranties and
Covenants. The respective representations and warranties set forth in or made
pursuant to this Agreement, and the respective obligations of the parties hereto
under Sections 7 and 11 of this Agreement, will remain in full force and effect,
regardless of any investigation or statement as to the result thereof made by or
on behalf of any party and will survive payment for the various transfers
referred to herein and delivery of the Certificates or termination of this
Agreement.

            Section 12. [Reserved]

            Section 13. Expenses; Recording Costs. Seller agrees to reimburse
the Trustee or its designee all recording and filing fees incurred in connection
with the recording or filing of the Mortgage Loan Documents listed in Section 3
of this Agreement.

            Section 14. Notices. All communications hereunder will be in writing
and effective only upon receipt, and, (a) if sent to Depositor, will be mailed,
delivered or telecopied and confirmed to it at Credit Suisse First Boston
Mortgage Securities Corp., Eleven Madison Avenue, 5th Floor, New York, New York
10010, Attention: Allan J. Baum, Telecopy No.: (212) 325-8162; and (b) if sent
to Seller, will be mailed, delivered or telecopied to it at PNC Bank, National
Association, One PNC Plaza, 19th Floor, 249 Fifth Avenue, Pittsburgh,
Pennsylvania 15222, attention: Kristina K. Williams, Telecopy No.: (412)
705-1645 with a copy to Gretchen Lengel Kelly, Esq., PNC Bank, National
Association, One PNC Plaza, 19th Floor, 249 Fifth Avenue, Pittsburgh,
Pennsylvania 15222, Telecopy No. (412) 762-4334, or in the case of any such
party, to such other address or telecopy number as such party may hereafter
furnish to the other party by like notice.

            Section 15. Examination of Mortgage Files. Upon reasonable notice,
Seller, prior to the Closing Date, will make the Mortgage Files available to
Depositor or its agent for examination during normal business hours at Seller's
offices or such other location as shall otherwise be agreed upon by Depositor
and Seller. The fact that Depositor or its agent has conducted or has failed to
conduct any partial or complete examination of the Mortgage Files shall not
affect the rights of Depositor or the Trustee (for the benefit of the
Certificateholders) to demand cure, repurchase, or other relief as provided
herein.

            Section 16. Successors. This Agreement shall inure to the benefit of
and shall be binding upon Seller and Depositor and their respective successors,
permitted assigns and legal representatives, and nothing expressed in this
Agreement is intended or shall be construed to give any other person any legal
or equitable right, remedy or claim under or in respect of this Agreement, or
any provisions herein contained, this Agreement and all conditions and
provisions hereof being intended to be and being for the sole and exclusive
benefit of such persons and for the benefit of no other person; it being
understood that (a) the indemnities of Seller contained in that certain
Indemnification Agreement dated August 17, 2001 among Seller, Depositor and the
Underwriters, subject to all limitations therein contained, shall also be for
the benefit of the officers and directors of Depositor, the Underwriters and the
Initial Purchaser and any person or persons who control Depositor, the
Underwriters and the Initial Purchaser within the meaning of Section 15 of the
Securities Act or Section 20 of the 1934 Act, and (b) the rights of Depositor
pursuant to this Agreement, subject to all limitations herein contained,
including those set forth in Section 9 of this Agreement, may be assigned to the
Trustee as may be required to effect the purposes of the Pooling and Servicing
Agreement and, upon such assignment, the Trustee shall succeed to such rights of
Depositor hereunder. No owner of a Certificate issued pursuant to the Pooling
and Servicing Agreement shall be deemed a successor because of such ownership.

            Section 17. Governing Law. THIS AGREEMENT SHALL BE GOVERNED AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK APPLICABLE TO
AGREEMENTS TO BE MADE AND PERFORMED ENTIRELY WITHIN SUCH STATE WITHOUT GIVING
EFFECT TO CHOICE OF LAW PRINCIPLES.

            Section 18. Severability. If any provision of this Agreement shall
be prohibited or invalid under applicable law, this Agreement shall be
ineffective only to such extent, without invalidating the remainder of this
Agreement.

            Section 19. Further Assurances. Depositor and Seller agree to
execute and deliver such instruments and take such actions as the other parties
may, from time to time, reasonably request in order to effectuate the purpose
and to carry out the terms of this Agreement.

            Section 20. Counterparts. This Agreement may be executed in
counterparts (and by each of the parties hereto on different counterparts), each
of which when so executed and delivered will be an original, and all of which
together will be deemed to constitute but one and the same instrument.

            Section 21. Treatment as Security Agreement. It is the express
intent of the parties hereto that the conveyance of the Mortgage Loans by Seller
to Depositor as provided in this Agreement be, and be construed as, a sale of
the Mortgage Loans by Seller to Depositor. It is, further, not the intention of
the parties that such conveyance be deemed a pledge of the Mortgage Loans by
Seller to Depositor to secure a debt or other obligation of Seller. However, in
the event that, notwithstanding the intent of the parties, the Mortgage Loans
are held to be property of Seller or if for any reason this Agreement is held or
deemed to create a security interest in the Mortgage Loans:

            (a) this Agreement shall hereby create a security agreement within
the meaning of Articles 8 and 9 of the Uniform Commercial Code in effect in the
applicable state;

            (b) the conveyance provided for in this Agreement shall hereby grant
from Seller to Depositor a security interest in and to all of Seller's right,
title, and interest, whether now owned or hereafter acquired, in and to:

            (i) all accounts, contract rights, general intangibles, chattel
      paper, instruments, documents, money, deposit accounts, certificates of
      deposit, goods, letters of credit, advices of credit and investment
      property consisting of, arising from or relating to any of the property
      described in the Mortgage Loans, including the related Notes, Mortgages
      and title, hazard and primary mortgage insurance policies identified on
      the Mortgage Loan Schedule, including all replacement Mortgage Loans, and
      all distributions with respect thereto payable after the Cut-off Date;

            (ii) all accounts, contract rights, general intangibles, chattel
      paper, instruments, documents, money, deposit accounts, certificates of
      deposit, goods, letters of credit, advices of credit and investment
      property arising from or by virtue of the disposition of, or collections
      with respect to, or insurance proceeds payable with respect to, or claims
      against other persons with respect to, all or any part of the collateral
      described in (i) above (including any accrued discount realized on
      liquidation of any investment purchased at a discount), in each case,
      payable after the Cut-off Date; and

            (iii) all cash and non-cash proceeds of the collateral described in
      (i) and (ii) above payable after the Cut-off Date;

            (c) the possession by Depositor or its assignee of the Notes and
such other goods, letters of credit, advices of credit, instruments, money,
documents, chattel paper or certificated securities shall be deemed to be
possession by the secured party or possession by a purchaser or a person
designated by him or her, for purposes of perfecting the security interest
pursuant to the Uniform Commercial Code (including, without limitation, Sections
9-306, 9-313 and 9-314 thereof) as in force in the relevant jurisdiction; and

            (d) notifications to persons holding such property, and
acknowledgments, receipts, confirmations from persons holding such property,
shall be deemed to be notifications to, or acknowledgments, receipts or
confirmations from, financial intermediaries, bailees or agents of, or persons
holding for (as applicable), Depositor or its assignee for the purpose of
perfecting such security interest under applicable law. The Seller at the
direction of the Depositor or its assignee, shall, to the extent consistent with
this Agreement, take such actions as may be necessary to ensure that, if this
Agreement were deemed to create a security interest in the Mortgage Loans and
the proceeds thereof, such security interest would be a perfected security
interest of first priority under applicable law and will be maintained as such
throughout the term of this Agreement. In connection herewith, Depositor and its
assignee shall have all of the rights and remedies of a secured party and
creditor under the Uniform Commercial Code as in force in the relevant
jurisdiction.

            Section 22. Recordation of Agreement. To the extent permitted by
applicable law, this Agreement is subject to recordation following the Closing
Date in all appropriate public offices for real property records in all the
counties or other comparable jurisdictions in which any or all of the properties
subject to the Mortgages are situated, and in any other appropriate public
recording office or elsewhere, such recordation to be effected by Seller at
Seller's expense at the direction of Depositor accompanied by an Opinion of
Counsel to the effect that such recordation materially and beneficially affects
the interests of Depositor.

                                      * * *

<PAGE>

            IN WITNESS WHEREOF, the parties hereto have caused this Mortgage
Loan Purchase Agreement to be duly executed and delivered as the date first
above written.

                                       PNC BANK, NATIONAL ASSOCIATION,
                                          as Seller

                                       By:____________________________________
                                          Name:
                                          Title:

                                       CREDIT SUISSE FIRST BOSTON MORTGAGE
                                          SECURITIES CORP.,
                                          as Depositor

                                       By:____________________________________
                                          Name:
                                          Title:   Vice President

<PAGE>

                                                                      SCHEDULE I

                          SCHEDULE OF TRANSACTION TERMS

            This Schedule of Transaction Terms is appended to and incorporated
by reference in the Mortgage Loan Purchase Agreement (the "Agreement"), dated as
of August 1, 2001, between PNC Bank, National Association (the "Seller") and
Credit Suisse First Boston Mortgage Securities Corp. (the "Depositor").
Capitalized terms used herein without definition have the meanings given them in
or by reference in the Agreement or, if not defined in the Agreement, in the
Pooling and Servicing Agreement, the Underwriting Agreement.

            "Affiliate" means with respect to any specified Person, any other
Person controlling or controlled by or under common control with such specified
Person.

            "Borrower" means the borrower under the Mortgage Loan.

            "Certificate Purchase Agreement" means the Certificate Purchase
Agreement, dated August 17, 2001, between Depositor and the Initial Purchasers.

            "Certificates" means each class of the Credit Suisse First Boston
Mortgage Securities Corp. Commercial Mortgage Pass-Through Certificates, Series
2001-CP4.

            "Closing Date" means August 28, 2001.

            "Code" means the Internal Revenue Code of 1986, as amended.

            "Crossed Loan" means any Mortgage Loan which is cross-defaulted and
cross-collateralized with any other Mortgage Loan.

            "Cut-off Date" means, the applicable Due Date for each Mortgage Loan
occurring in August 2001.

            "Environmental Report" means the environmental audit report with
respect to each Mortgaged Property delivered to Seller in connection with the
related Mortgage, if any.

            "Exception Report" means exceptions with respect to the
representations and warranties made by the Seller as to the Mortgage Loans in
Section 6(a)(xii) and under the written certificate described in Section
4(b)(iii), which exceptions are set forth in Schedule V attached hereto and made
a part hereof.

            "Initial Purchasers" means Credit Suisse First Boston Corporation
and PNC Capital Markets, Inc.

            "Loan Agreement" means, with respect to any Mortgage Loan, the loan
agreement, if any, between the Originator and the Borrower, pursuant to which
such Mortgage Loan was made.

            "Mortgage Loan Purchase Price" means the amount described in Section
2 of the Agreement.

            "Mortgage Loan Documents" means, collectively, the documents and
instruments pertaining to a Mortgage Loan to be included in either the related
Mortgage File or the related Servicer File.

            "Mortgage File" means, collectively, the documents and instruments
pertaining to a Mortgage Loan required to be included in the related Mortgage
File pursuant to Section 3 (subject to the proviso in Section 1).

            "Mortgage Loans" means the mortgage loans to be sold to Depositor
pursuant to the Agreement, specifically identified in the Mortgage Loan Schedule
to the Agreement.

            "Offered Certificates" means the Class A-1, Class A-2, Class A-3,
Class A-4, Class B, Class C and Class D Certificates.

            "Offering Circular" means the confidential offering circular dated
August 17, 2001, describing certain classes of the Certificates.

            "Originator" means any institution which originated a Mortgage Loan
for a related Borrower.

            "Pooling and Servicing Agreement" means the Pooling and Servicing
Agreement creating the Trust Fund and the interests therein, dated as of August
1, 2001, among the Servicer, the Special Servicer, Depositor and the Trustee,
including the Mortgage Loan Schedule annexed thereto.

            "Primary Collateral" means with respect to any Crossed Loan, that
portion of the Mortgaged Property designated as directly securing such Crossed
Loan and excluding any Mortgaged Property as to which the related lien may only
be foreclosed upon by exercise of the cross-collaterization provisions of such
Crossed Loan.

            "Prospectus" means the Prospectus, dated March 5, 2001.

            "Prospectus Supplement" means the Prospectus Supplement, dated
August 17, 2001, relating to the Offered Certificates.

            "Servicer File" means, collectively, all documents, records and
copies pertaining to a Mortgage Loan which are required to be included in the
related Servicer File pursuant to Section 3 (subject to the proviso in Section
1).

            "Underwriters" means Credit Suisse First Boston Corporation, PNC
Capital Markets, Inc., Lehman Brothers Inc. and Salomon Smith Barney, Inc.

            "Underwriting Agreement" means the Underwriting Agreement, dated
August 17, 2001, between Depositor and the Underwriters.

<PAGE>

                                                                  EXECUTION COPY

                                                                     SCHEDULE II

                             MORTGAGE LOAN SCHEDULE

<PAGE>

                                                                  EXECUTION COPY

                                                                    SCHEDULE III

                   MORTGAGE LOANS CONSTITUTING MORTGAGE GROUPS

                                     [NONE]

<PAGE>

                                                                  EXECUTION COPY

                                                                     SCHEDULE IV

                         MORTGAGE LOANS WITH LOST NOTES

                                     [NONE]

<PAGE>

                                                                  EXECUTION COPY

                                                                      SCHEDULE V

                             EXCEPTIONS TO SELLER'S
                         REPRESENTATIONS AND WARRANTIES

            Reference is made to the Representations and Warranties contained in
Exhibit A corresponding to the roman numerals listed below:

Exception to Section (xxvi):

            Northeast Corporate Center (Pro Supp #10) - This Mortgage Loan does
not provide for acceleration of indebtedness if, without the consent of the
holder of the Mortgage Loan, a majority interest in the related Borrower is
transferred by virtue of an involuntary change in ownership resulting from a
death or physical or mental disability and does not require the mortgagor to pay
the holder's fees and costs associated therewith.

Exceptions to Section (xxx):

            Sharp Rees Stealy Building (Pro Supp #32) - The related lessor has
not agreed in writing that the related ground lease may not be amended or
modified without the prior written consent of the lender and that any such
action without such consent is not binding on the lender, its successors or
assigns.

Exception to Section (xxxiv):

            Hampton Inn (Pro Supp #64) - Subordinated mortgage in favor of
developer of adjoining business park to secure its advances under an agreement
to enforce use and development restrictions, including a right to pay off the
Mortgage Loan upon borrower's default.

Exception to Section (xxxvi):

            Canyon Walk Apartments (Pro Supp #71) - The Borrower can incur debt
to an affiliate of SunAmerica Inc. (the 99% limited partner of the Borrower).,
provided that any such debt would be subordinated to the Mortgage Loan and
subject to the Non-Recourse Indemnification Agreement between the Lender and
SunAmerica Inc., and no such debt may be secured by the Mortgaged Property

<PAGE>

                                                                  EXECUTION COPY

EXHIBIT A

                    REPRESENTATIONS AND WARRANTIES OF SELLER
                          REGARDING THE MORTGAGE LOANS

            (i) Immediately prior to the sale, transfer and assignment to the
Depositor, no Note or Mortgage was subject to any assignment (other than
assignments which show a complete chain of assignment to the Seller),
participation or pledge, and the Seller had good and marketable title to, and
was the sole owner of, the related Mortgage Loan;

            (ii) The Seller has full right and authority to sell, assign and
transfer such Mortgage Loan and the assignment to the Depositor constitutes a
legal, valid and binding assignment of such Mortgage Loan;

            (iii) The Seller is transferring such Mortgage Loan free and clear
of any and all liens, pledges, charges or security interests of any nature
encumbering such Mortgage Loan;

            (iv) Each related Note, Mortgage, assignment of leases (if any) and
other agreement executed by or for the benefit of the related borrower, any
guarantor or their successors or assigns in connection with such Mortgage Loan
is the legal, valid and binding obligation of the related borrower, enforceable
in accordance with its terms, except as such enforcement may be limited by
bankruptcy, insolvency, reorganization, moratorium or other laws affecting the
enforcement of creditors' rights or by general principles of equity (regardless
of whether such enforceability is considered in a proceeding in equity or at
law); and there is no valid defense, counterclaim, or right of rescission
available to the related borrower with respect to such Note, Mortgage,
assignment of leases and other agreements, except as the enforcement thereof may
be limited by bankruptcy, insolvency, reorganization, moratorium or other laws
affecting the enforcement of creditors' rights or by general principles of
equity (regardless of whether such enforceability is considered in a proceeding
in equity or at law);

            (v) Each related assignment of leases creates a valid first priority
collateral assignment of, or a valid first priority lien or security interest
in, certain rights under the related lease or leases, subject only to a license
granted to the related borrower to exercise certain rights and to perform
certain obligations of the lessor under such lease or leases, including the
right to operate the related leased property, except as the enforcement thereof
may be limited by bankruptcy, insolvency, reorganization, moratorium or other
laws affecting the enforcement of creditors' rights or by general principles of
equity (regardless of whether such enforceability is considered in a proceeding
in equity or at law); no person other than the related borrower owns any
interest in any payments due under such lease or leases that is superior to or
of equal priority with the lender's interest therein;

            (vi) Each related assignment of Mortgage from the Seller to the
Depositor and related assignment of the assignment of leases, if any, or
assignment of any other agreement executed by or for the benefit of the related
borrower, any guarantor or their successors or assigns in connection with such
Mortgage Loan from the Seller to the Depositor constitutes the legal, valid and
binding assignment from the Seller to the Depositor, except as the enforcement
thereof may be limited by bankruptcy, insolvency, reorganization, liquidation,
receivership, moratorium or other laws relating to or affecting the enforcement
of creditors' rights or by general principles of equity (regardless of whether
such enforceability is considered in a proceeding in equity or at law);

            (vii) Since origination, and except as set forth in the related
mortgage file, (a) such Mortgage Loan has not been modified, altered, satisfied,
canceled, subordinated or rescinded and (b) each related Mortgaged Property has
not been released from the lien of the related Mortgage in any manner which
materially interferes with the security intended to be provided by such
Mortgage;

            (viii) Each related Mortgage is a valid and enforceable first lien
on the related Mortgaged Property (subject to Permitted Encumbrances (as defined
below)), except as the enforcement thereof may be limited by bankruptcy,
insolvency, reorganization, moratorium or other laws affecting the enforcement
of creditors' rights or by general principles of equity (regardless of whether
such enforceability is considered in a proceeding in equity or at law); and such
Mortgaged Property is free and clear of any mechanics' and materialmen's liens
which are prior to or equal with the lien of the related Mortgage, except those
which are insured against by a lender's title insurance policy (as described
below). A UCC financing statement has been filed and/or recorded (or sent for
filing or recording) in all places necessary to perfect a valid security
interest in the personal property necessary to operate the Mortgaged Property;
any security agreement, chattel mortgage or equivalent document related to and
delivered in connection with the Mortgage Loan establishes and creates a valid
and enforceable lien on property described therein, except as such enforcement
may be limited by bankruptcy, insolvency, reorganization, moratorium or other
laws affecting the enforcement of creditors' rights or by general principles of
equity (regardless of whether such enforceability is considered in a proceeding
in equity or at law);

            (ix) The Seller has not taken any action that would cause the
representations and warranties made by the related borrower in the related
Mortgage Loan Documents not to be true;

            (x) The Seller has no knowledge that the material representations
and warranties made by the related borrower in the related Mortgage Loan
Documents are not true in any material respect;

            (xi) The lien of each related Mortgage is a first priority lien on
the fee or leasehold interest of the related borrower in the principal amount of
such Mortgage Loan or allocated loan amount of the portions of the Mortgaged
Property covered thereby (as set forth in the related Mortgage) after all
advances of principal and is insured by an ALTA lender's title insurance policy
(or a binding commitment therefor), or its equivalent as adopted in the
applicable jurisdiction, insuring the Seller and its successors and assigns as
to such lien, subject only to (a) the lien of current real property taxes,
ground rents, water charges, sewer rents and assessments not yet delinquent or
accruing interest or penalties, (b) covenants, conditions and restrictions,
rights of way, easements and other matters of public record, none of which,
individually or in the aggregate, materially interferes with the current use of
the Mortgaged Property or the security intended to be provided by such Mortgage
or with the borrower's ability to pay its obligations when they become due or
the value of the Mortgaged Property and (c) the exceptions (general and
specific) and exclusions set forth in such policy, none of which, individually
or in the aggregate, materially interferes with the current general use of the
Mortgaged Property or materially interferes with the security intended to be
provided by such Mortgage or with the related borrower's ability to pay its
obligations when they become due or the value of the Mortgaged Property (items
(a), (b) and (c) collectively, "Permitted Encumbrances"); the premium for such
policy was paid in full; such policy (or if it is yet to be issued, the coverage
to be afforded thereby) is issued by a title insurance company licensed to issue
policies in the state in which the related Mortgaged Property is located (unless
such state is Iowa) and is assignable (with the related Mortgage Loan) to the
Depositor and the Trustee without the consent of or any notification to the
insurer, and is in full force and effect upon the consummation of the
transactions contemplated by the Mortgage Loan Purchase Agreement; no claims
have been made under such policy and the Seller has not undertaken any action or
omitted to take any action, and has no knowledge of any such act or omission,
which would impair or diminish the coverage of such policy;

            (xii) The proceeds of such Mortgage Loan have been fully disbursed
and there is no requirement for future advances thereunder, and no future
advances have been made which are not reflected in the related mortgage file;

            (xiii) Except as set forth in a property inspection report or
engineering report prepared in connection with the origination of the Mortgage
Loan, as of the later of the date of origination of such Mortgage Loan or the
most recent inspection of the related Mortgaged Property by the Seller, as
applicable, and to the knowledge of Seller as of the date hereof, each related
Mortgaged Property is free of any material damage that would affect materially
and adversely the value of such Mortgaged Property as security for the Mortgage
Loan or reserves have been established to cover the costs to remediate such
damage and, as of the closing date for each Mortgage Loan and, to the Seller's
knowledge, as of the date hereof, there is no proceeding pending for the total
or partial condemnation of such Mortgaged Property that would have a material
adverse effect on the value of the Mortgaged Property;

            (xiv) The Seller has inspected or caused to be inspected each
related Mortgaged Property within the past twelve months, or the originator of
the Mortgage Loan inspected or caused to be inspected each related Mortgage
Property within three months of origination of the Mortgage Loan;

            (xv) No Mortgage Loan has a shared appreciation feature, any other
contingent interest feature or a negative amortization feature other than the
ARD Loans which may have negative amortization from and after the Anticipated
Repayment Date;

            (xvi) Each Mortgage Loan is a whole loan and contains no equity
participation by Seller;

            (xvii) The Mortgage Rate (exclusive of any default interest, late
charges, or prepayment premiums) of such Mortgage Loan complied as of the date
of origination with, or was exempt from, applicable state or federal laws,
regulations and other requirements pertaining to usury. Except to the extent any
noncompliance did not materially and adversely affect the value of the related
Mortgaged Property, the security provided by the Mortgage or the related
borrower's operations at the related Mortgaged Property, any and all other
requirements of any federal, state or local laws, including, without limitation,
truth-in-lending, real estate settlement procedures, equal credit opportunity or
disclosure laws, applicable to such Mortgage Loan have been complied with as of
the date of origination of such Mortgage Loan;

            (xviii) Neither the Seller nor to the Seller's knowledge, any
originator, committed any fraudulent acts during the origination process of any
Mortgage Loan and the origination, servicing and collection of each Mortgage
Loan is in all respects legal, proper and prudent in accordance with customary
commercial mortgage lending standards, and no other person has been granted or
conveyed the right to service the Mortgage Loans or receive any consideration in
connection therewith, except as provided in the Pooling and Servicing Agreement
or any permitted subservicing agreements;

            (xix) All taxes and governmental assessments that became due and
owing prior to the date hereof with respect to each related Mortgaged Property
and that are or may become a lien of priority equal to or higher than the lien
of the related Mortgage have been paid or an escrow of funds has been
established and such escrow (including all escrow payments required to be made
prior to the delinquency of such taxes and assessments) is sufficient to cover
the payment of such taxes and assessments;

            (xx) All escrow deposits and payments required pursuant to each
Mortgage Loan are in the possession, or under the control, of the Seller or its
agent and there are no deficiencies (subject to any applicable grace or cure
periods) in connection therewith and all such escrows and deposits are being
conveyed by the Seller to the Depositor and identified as such with appropriate
detail;

            (xxi) Each related Mortgaged Property is insured by a fire and
extended perils insurance policy, issued by an insurer meeting the requirements
of the Pooling and Servicing Agreement, in an amount not less than the lesser of
the principal amount of the related Mortgage Loan and the replacement cost (with
no deduction for physical depreciation) and not less than the amount necessary
to avoid the operation of any co-insurance provisions with respect to the
related Mortgaged Property; each related Mortgaged Property is also covered by
business interruption or rental loss insurance which covers a period of not less
than 12 months and comprehensive general liability insurance in amounts
generally required by prudent commercial mortgage lenders for similar
properties; all premiums on such insurance policies required to be paid as of
the date hereof have been paid; such insurance policies require prior notice to
the insured of termination or cancellation, and no such notice has been received
by the Seller; such insurance names the lender under the Mortgage Loan and its
successors and assigns as a named or additional insured; each related Mortgage
Loan obligates the related borrower to maintain all such insurance and, at such
borrower's failure to do so, authorizes the lender to maintain such insurance at
the borrower's cost and expense and to seek reimbursement therefor from such
borrower;

            (xxii) There is no monetary default, breach, violation or event of
acceleration existing under the related Mortgage Loan. To the Seller's
knowledge, there is no (a) non-monetary default, breach, violation or event of
acceleration existing under the related Mortgage Loan or (b) event (other than
payments due but not yet delinquent) which, with the passage of time or with
notice and the expiration of any grace or cure period, would and does constitute
a default, breach, violation or event of acceleration, which default, breach,
violation or event of acceleration, in the case of either (a) or (b), materially
and adversely affects the value of the Mortgage Loan or the related Mortgaged
Property; provided, however, that this representation and warranty does not
address or otherwise cover any default, breach, violation or event of
acceleration that specifically pertains to any matter otherwise covered by any
other representation or warranty made by the Seller in any of paragraphs (xiii),
(xix), (xxiii), (xxv), (xxvii), and (xxix) of this Exhibit A-1;

            (xxiii) No Mortgage Loan has been more than 30 days delinquent in
making required payments since origination and as of the Cut-off Date no
Mortgage Loan is 30 or more days delinquent in making required payments;

            (xxiv) (a) Each related Mortgage contains provisions so as to render
the rights and remedies of the holder thereof adequate for the practical
realization against the Mortgaged Property of the principal benefits of the
security, including realization by judicial or, if applicable, non-judicial
foreclosure, and (b) there is no exemption available to the borrower which would
interfere with such right to foreclose, except, in the case of either (a) or
(b), as the enforcement of the Mortgage may be limited by bankruptcy,
insolvency, reorganization, moratorium, redemption or other laws affecting the
enforcement of creditors' rights or by general principles of equity (regardless
of whether such enforceability is considered in a proceeding in equity or at
law). To the Seller's knowledge, no borrower is a debtor in a state or federal
bankruptcy or insolvency proceeding;

            (xxv) At origination, each borrower represented and warranted in all
material respects that to its knowledge, except as set forth in certain
environmental reports, it has not used, caused or permitted to exist and will
not use, cause or permit to exist on the related Mortgaged Property any
hazardous materials in any manner which violates federal, state or local laws,
ordinances, regulations, orders, directives or policies governing the use,
storage, treatment, transportation, manufacture, refinement, handling,
production or disposal of hazardous materials or other environmental laws; the
related borrower or an affiliate thereof agreed to indemnify, defend and hold
the mortgagee and its successors and assigns harmless from and against losses,
liabilities, damages, injuries, penalties, fines, expenses, and claims of any
kind whatsoever (including attorneys' fees and costs) paid, incurred or suffered
by, or asserted against, any such party resulting from a breach of the foregoing
representations, warranties or covenants given by the borrower in connection
with such Mortgage Loan. A Phase I environmental report and with respect to
certain Mortgage Loans, a Phase II environmental report, was conducted by a
reputable environmental engineer in connection with such Mortgage Loan, which
report did not indicate any material non-compliance with applicable
environmental laws or material existence of hazardous materials or, if any
material non-compliance or material existence of hazardous materials was
indicated in any such report, then at least one of the following statements is
true: (A) funds reasonably estimated to be sufficient to cover the cost to cure
any material non-compliance with applicable environmental laws or material
existence of hazardous materials have been escrowed by the related borrower and
held by the related mortgagee; (B) an operations or maintenance plan has been
required to be instituted by the related borrower; (C) the environmental
condition identified in the related environmental report was remediated or
abated in all material respects prior to the date hereof and a no further action
or closure letter was obtained from the applicable governmental regulatory
authority (or the environmental issue affecting the related Mortgaged Property
was otherwise listed by such governmental authority as "closed"); or (D) a
lender's environmental insurance policy was obtained and is a part of the
related mortgage file. Notwithstanding the preceding sentence, with respect to
certain Mortgage Loans with an original principal balance of less than
$3,000,000, no environmental report may have been obtained, but a lender's
secured creditor impairment environmental insurance policy was obtained with
respect to each such Mortgage Loan and is a part of the related mortgage file.
Each of such environmental insurance policies is in full force and effect, the
premiums for such policies have been paid in full and the Trustee is named as an
insured under each of such policies. To the best of the Seller's knowledge, in
reliance on such environmental reports and except as set forth in such
environmental reports, each Mortgaged Property is in material compliance with
all applicable federal, state and local environmental laws, and to the best of
the Seller's knowledge, no notice of violation of such laws has been issued by
any governmental agency or authority, except, in all cases, as indicated in such
environmental reports or other documents previously provided to the Rating
Agencies; and the Seller has not taken any action which would cause the
Mortgaged Property to not be in compliance with all federal, state and local
environmental laws pertaining to environmental hazards;

            (xxvi) (1) Each Mortgage Loan contains provisions for the
acceleration of the payment of the unpaid principal balance of such Mortgage
Loan if, without the consent of the holder of the Mortgage (and the Mortgage
requires the mortgagor to pay all fees and expenses associated with obtaining
such consent), the related Mortgaged Property is directly or indirectly
transferred or sold, and (2) except with respect to transfers of certain
interests in the related Borrower to persons already holding interests in the
Borrower, their family members, affiliated companies and other estate planning
related transfers that satisfy certain criteria specified in the related
Mortgage (which criteria is consistent with the practices of prudent commercial
mortgage lenders), each Mortgage Loan with a Stated Principal Balance of over
$20,000,000 also contains the provisions for the acceleration of the payment of
the unpaid principal balance of such Mortgage Loan if, without the consent of
the holder of the Mortgage, (and the Mortgage requires the mortgagor to pay all
fees and expenses associated with obtaining such consent) a majority interest in
the related Borrower is directly or indirectly transferred or sold;

            (xxvii) All improvements included in the related appraisal are
within the boundaries of the related Mortgaged Property, except for
encroachments onto adjoining parcels for which the Seller has obtained title
insurance against losses arising therefrom or that do not materially and
adversely affect the value of such Mortgaged Property. No improvements on
adjoining parcels encroach onto the related Mortgaged Property except for
encroachments that do not materially and adversely affect the value of such
Mortgaged Property, the security provided by the Mortgage or the related
borrower's operations at the Mortgaged Property;

            (xxviii) The information pertaining to the Mortgage Loans which is
set forth in the mortgage loan schedule attached as an exhibit to this Mortgage
Loan Purchase Agreement is complete and accurate in all material respects as of
the dates of the information set forth therein (or, if not set forth therein, as
of the Cut-Off Date);

            (xxix) With respect to any Mortgage Loan where all or a material
portion of the estate of the related borrower therein is a leasehold estate, and
the related Mortgage does not also encumber the related lessor's fee interest in
such Mortgaged Property, based upon the terms of the ground lease and any
estoppel received from the ground lessor, the Seller represents and warrants
that:

            (A) The ground lease or a memorandum regarding such ground lease has
      been duly recorded. The ground lease permits the interest of the lessee to
      be encumbered by the related Mortgage and does not restrict the use of the
      related Mortgaged Property by such lessee, its successors or assigns in a
      manner that would adversely affect the security provided by the related
      Mortgage. To the Seller's best knowledge, there has been no material
      change in the terms of the ground lease since its recordation, except by
      any written instruments which are included in the related mortgage file;

            (B) The lessor under such ground lease has agreed in a writing
      included in the related mortgage file that the ground lease may not be
      amended, modified, canceled or terminated without the prior written
      consent of the lender and that any such action without such consent is not
      binding on the lender, its successors or assigns;

            (C) The ground lease has an original term (or an original term plus
      one or more optional renewal terms, which, under all circumstances, may be
      exercised, and will be enforceable, by the lender) that extends not less
      than 20 years beyond the stated maturity of the related Mortgage Loan;

            (D) Based on the title insurance policy (or binding commitment
      therefor) obtained by the Seller, the ground lease is not subject to any
      liens or encumbrances superior to, or of equal priority with, the
      Mortgage, subject to Permitted Encumbrances and liens that encumber the
      ground lessor's fee interest;

            (E) The ground lease is assignable to the lender under the leasehold
      estate and its assigns without the consent of the lessor thereunder;

            (F) As of the Closing Date, the ground lease is in full force and
      effect, the Seller has no actual knowledge that any default beyond
      applicable notice and grace periods has occurred, and there is no existing
      condition which, but for the passage of time or giving of notice, would
      result in a default under the terms of the ground lease;

            (G) The ground lease or ancillary agreement between the lessor and
      the lessee requires the lessor to give notice of any default by the lessee
      to the lender;

            (H) A lender is permitted a reasonable opportunity (including, where
      necessary, sufficient time to gain possession of the interest of the
      lessee under the ground lease through legal proceedings, or to take other
      action so long as the lender is proceeding diligently) to cure any default
      under the ground lease which is curable after the receipt of notice of any
      default before the lessor may terminate the ground lease. All rights of
      the lender under the ground lease and the related Mortgage (insofar as it
      relates to the ground lease) may be exercised by or on behalf of the
      lender;

            (I) The ground lease does not impose any restrictions on subletting
      that would be viewed as commercially unreasonable by an institutional
      investor. The lessor is not permitted to disturb the possession, interest
      or quiet enjoyment of any subtenant of the lessee in the relevant portion
      of the Mortgaged Property subject to the ground lease for any reason, or
      in any manner, which would adversely affect the security provided by the
      related Mortgage;

            (J) Under the terms of the ground lease and the related Mortgage,
      any related insurance proceeds or condemnation award (other than in
      respect of a total or substantially total loss or taking) will be applied
      either to the repair or restoration of all or part of the related
      Mortgaged Property, with the lender or a trustee appointed by it having
      the right to hold and disburse such proceeds as repair or restoration
      progresses, or to the payment of the outstanding principal balance of the
      Mortgage Loan, together with any accrued interest, except that in the case
      of condemnation awards, the ground lessor may be entitled to a portion of
      such award;

            (K) Under the terms of the ground lease and the related Mortgage,
      any related insurance proceeds, or condemnation award in respect of a
      total or substantially total loss or taking of the related Mortgaged
      Property will be applied first to the payment of the outstanding principal
      balance of the Mortgage Loan, together with any accrued interest (except
      as provided by applicable law or in cases where a different allocation
      would not be viewed as commercially unreasonable by any institutional
      investor, taking into account the relative duration of the ground lease
      and the related Mortgage and the ratio of the market value of the related
      Mortgaged Property to the outstanding principal balance of such Mortgage
      Loan). Until the principal balance and accrued interest are paid in full,
      neither the lessee nor the lessor under the ground lease will have an
      option to terminate or modify the ground lease without the prior written
      consent of the lender as a result of any casualty or partial condemnation,
      except to provide for an abatement of the rent; and

            (L) Provided that the lender cures any defaults which are
      susceptible to being cured, the lessor has agreed to enter into a new
      lease upon termination of the ground lease for any reason, including
      rejection of the ground lease in a bankruptcy proceeding;

            (xxx) With respect to any Mortgage Loan where all or a material
portion of the estate of the related borrower therein is a leasehold estate, but
the related Mortgage also encumbers the related lessor's fee interest in such
Mortgaged Property: (a) such lien on the related fee interest is evidenced by
the related Mortgage, (b) such Mortgage does not by its terms provide that it
will be subordinated to the lien of any other mortgage or encumbrance upon such
fee interest, (c) upon the occurrence of a default under the terms of such
Mortgage by the related borrower, any right of the related lessor to receive
notice of, and to cure, such default granted to such lessor under any agreement
binding upon the Seller would not be considered commercially unreasonable in any
material respect by prudent commercial mortgage lenders, (d) the related lessor
has agreed in a writing included in the related mortgage file that the related
ground lease may not be amended or modified without the prior written consent of
the lender and that any such action without such consent is not binding on the
lender, its successors or assigns, and (e) the related ground lease is in full
force and effect, and the Seller has no actual knowledge that any default beyond
applicable notice and grace periods has occurred or that there is any existing
condition which, but for the passage of time or giving of notice, would result
in a default under the terms of such ground lease;

            (xxxi) With respect to Mortgage Loans that are cross-collateralized
or cross-defaulted, all other loans that are cross-collateralized by or
cross-defaulted with such Mortgage Loans are being transferred to the Depositor;

            (xxxii) Neither Seller nor any affiliate thereof has any obligation
to make any capital contribution to any borrower under a Mortgage Loan, other
than contributions made on or prior to the date hereof;

            (xxxiii) (1) The Mortgage Loan is directly secured by a Mortgage on
a commercial property or multifamily residential property, and (2) the fair
market value of such real property, as evidenced by an appraisal satisfying the
requirements of FIRREA conducted within 12 months of the origination of the
Mortgage Loan, was at least equal to 80% of the principal amount of the Mortgage
Loan (a) at origination (or if the Mortgage Loan has been modified in a manner
that constituted a deemed exchange under Section 1001 of the Code at a time when
the Mortgage Loan was not in default or default with respect thereto was not
reasonably foreseeable, the date of the last such modification) or (b) at the
date hereof; provided that the fair market value of the real property must first
be reduced by (A) the amount of any lien on the real property interest that is
senior to the Mortgage Loan and (B) a proportionate amount of any lien that is
in parity with the Mortgage Loan (unless such other lien secures a Mortgage Loan
that is cross-collateralized with such Mortgage Loan, in which event the
computation described in (a) and (b) shall be made on an aggregated basis);

            (xxxiv) There are no subordinate mortgages encumbering the related
Mortgaged Property, nor are there any preferred equity interests held by the
Seller or any mezzanine debt related to such Mortgaged Property, except as set
forth in the Prospectus Supplement, this Exhibit A or in the Exception Report to
this Mortgage Loan Purchase Agreement;

            (xxxv) The Mortgage Loan Documents executed in connection with each
Mortgage Loan having an original principal balance in excess of $10,000,000
require that the related borrower be a single-purpose entity (for this purpose,
"single-purpose entity" shall mean an entity, other than an individual, having
organizational documents which provide substantially to the effect that it is
formed or organized solely for the purpose of owning and operating one or more
Mortgaged Properties, is prohibited from engaging in any business unrelated to
such property and the related Mortgage Loan, does not have any assets other than
those related to its interest in the related Mortgaged Property or its
financing, or any indebtedness other than as permitted under the related
Mortgage Loan);

            (xxxvi) Each Mortgage Loan prohibits the related borrower from
mortgaging or otherwise encumbering the Mortgaged Property without the prior
written consent of the mortgagee or the satisfaction of debt service coverage or
similar criteria specified therein and, except in connection with trade debt and
equipment financings in the ordinary course of borrower's business, from
carrying any additional indebtedness, except, in each case, liens contested in
accordance with the terms of the Mortgage Loans;

            (xxxvii) Each borrower covenants in the Mortgage Loan documents that
it shall remain in material compliance with all material licenses, permits and
other legal requirements necessary and required to conduct its business;

            (xxxviii) Each Mortgaged Property (a) is located on or adjacent to a
dedicated road, or has access to an irrevocable easement permitting ingress and
egress, (b) is served by public utilities and services generally available in
the surrounding community or otherwise appropriate for the use in which the
Mortgaged Property is currently being utilized, and (c) constitutes one or more
separate tax parcels or is covered by an endorsement with respect to the matters
described in (a), (b) or (c) under the related title insurance policy (or the
binding commitment therefor);

            (xxxix) Based solely on a flood zone certification or a survey of
the related Mortgaged Property, if any portion of the improvements on the
Mortgaged Property is located in an area identified by the Federal Emergency
Management Agency or the Secretary of Housing and Urban Development as having
special flood hazards categorized as Zone "A" or Zone "V" and flood insurance is
available, the terms of the Mortgage Loan require the borrower to maintain flood
insurance, or at such borrower's failure to do so, authorizes the Lender to
maintain such insurance at the cost and expense of the borrower;

            (xl) To the knowledge of the Seller, with respect to each Mortgage
which is a deed of trust, a trustee, duly qualified under applicable law to
serve as such, currently so serves and is named in the deed of trust or has been
substituted in accordance with applicable law or may be substituted in
accordance with applicable law by the related mortgagee, and except in
connection with a trustee's sale after a default by the related borrower, no
fees are payable to such trustee;

            (xli) RESERVED.

            (xlii) Except as disclosed in the Exception Report to this Mortgage
Loan Purchase Agreement or the Prospectus Supplement, to the knowledge of the
Seller as of the date hereof, there was no pending action, suit or proceeding,
arbitration or governmental investigation against any borrower or Mortgaged
Property, an adverse outcome of which would materially and adversely affect such
borrower's ability to perform under the related Mortgage Loan;

            (xliii) No advance of funds has been made by the Seller to the
related borrower (other than mezzanine debt and the acquisition of preferred
equity interests by the Preferred Interest Holder, as disclosed in the
Prospectus Supplement), and no funds have, to the Seller's knowledge, been
received from any person other than, or on behalf of, the related borrower, for,
or on account of, payments due on the Mortgage Loan;

            (xliv) To the extent required under applicable law, as of the
Cut-off Date or as of the date that such entity held the Note, each holder of
the Note was authorized to transact and do business in the jurisdiction in which
each related Mortgaged Property is located, or the failure to be so authorized
did not materially and adversely affect the enforceability of such Mortgage
Loan;

            (xlv) All collateral for the Mortgage Loans is being transferred as
part of the Mortgage Loans;

            (xlvi) Except as disclosed in the Exception Report to this Mortgage
Loan Purchase Agreement or the Prospectus Supplement with respect to the Crossed
Loans and Multiple Property Loans, no Mortgage Loan requires the lender to
release any portion of the Mortgaged Property from the lien of the related
Mortgage except upon (a) payment in full or defeasance of the related Mortgage
Loan, (b) the satisfaction of certain legal and underwriting requirements, (c)
releases of unimproved out-parcels or (d) releases of portions of the Mortgaged
Property which will not have a material adverse effect on the value of the
collateral for the related Mortgage Loan;

            (xlvii) Except as provided in paragraphs (xxix) (J) and (K) above,
any insurance proceeds in respect of a casualty loss or taking will be applied
either to (a) the repair or restoration of all or part of the related Mortgaged
Property, with, in the case of all Mortgage Loans other than Credit Lease Loans
and with respect to all casualty losses or takings in excess of a specified
percentage of the related loan amount, the lender (or a trustee appointed by it)
having the right to hold and disburse such proceeds as the repair or restoration
progresses (except in any case where a provision entitling another party to hold
and disburse such proceeds would not be viewed as commercially unreasonable by a
prudent commercial mortgage lender) or (b) to the payment of the outstanding
principal balance of such Mortgage Loan together with any accrued interest
thereon;

            (xlviii) Each Form UCC-1 financing statement, if any, filed with
respect to personal property constituting a part of the related Mortgaged
Property and each Form UCC-2 or UCC-3 assignment, if any, of such financing
statement to the Seller was, and each Form UCC-3 assignment, if any, of such
financing statement in blank which the Trustee or its designee is authorized to
complete (but for the insertion of the name of the assignee and any related
filing information which is not yet available to the Seller) is, in suitable
form for filing in the filing office in which such financing statement was
filed;

            (xlix) To the Seller's knowledge, (a) each commercial lease covering
more than 10% (20% in the case of any Mortgage Loan having an original principal
balance less than $2,500,000) of the net leaseable area of the related Mortgaged
Property is in full force and effect and (b) there exists no default under any
such commercial lease either by the lessee thereunder or by the related borrower
that could give rise to the termination of such lease;

            (l) Based upon an opinion of counsel and/or other due diligence
considered reasonable by prudent commercial mortgage lenders, the improvements
located on or forming part of each Mortgaged Property comply with applicable
zoning laws and ordinances, or constitute a legal non-conforming use or
structure or, if any such improvement does not so comply, such non-compliance
does not materially and adversely affect the value of the related Mortgaged
Property. With respect to properties with a Stated Principal Balance of over
$10,000,000, if the related Mortgaged Property does not so comply, to the extent
the Seller is aware of such non-compliance, it has required the related Borrower
to obtain law and ordinance insurance coverage in amounts customarily required
by prudent commercial mortgage lenders;

            (li) Each Mortgage Loan constitutes a "qualified mortgage" within
the meaning of Section 860G(a)(3) of the Code (but without regard to the rule in
Treasury Regulation (as defined herein) Section 1.860G-2(f)(2) that treats a
defective obligation as a qualified mortgage or any substantially similar
successor provision) and all Prepayment Premiums and Yield Maintenance Charges
constitute "customary prepayment penalties" within the meaning of Treasury
Regulation Section 1.860G-1(b)(2);

            (lii) With respect to any Mortgage Loan that pursuant to the
Mortgage Loan Documents can be defeased, (i) the Mortgage Loan cannot be
defeased within two years after the Closing Date, (ii) the borrower can pledge
only United States government securities in an amount sufficient to make all
scheduled payments under the Mortgage Loan when due, (iii) the borrower is
required to provide independent certified public accountant's certification that
the collateral is sufficient to make such payments, (iv) the loan may be
required to be assumed by a single-purpose entity designated by the holder of
the Mortgage Loan, and (v) the borrower is required to provide an opinion of
counsel that the trustee has a perfected security interest in such collateral
prior to any other claim or interest;

            (liii) The Mortgage Loan Documents for each Mortgage Loan provide
that the related borrower thereunder shall be liable to the Seller for any
losses incurred by the Seller due to (i) the misapplication or misappropriation
of rents, insurance proceeds or condemnation awards, (ii) any willful act of
material waste, (iii) any breach of the environmental covenants contained in the
related Mortgage Loan Documents, and (iv) fraud;

            (liv) If such Mortgage Loan is an ARD Loan, it commenced amortizing
on its initial scheduled Due Date and provides that: (i) its Mortgage Rate will
increase by no more than two percentage points in connection with the passage of
its Anticipated Repayment Date and so long as the Mortgage Loan is an asset of
the Trust Fund; (ii) its Anticipated Repayment Date is not less than seven years
following the origination of such Mortgage Loan; (iii) no later than the related
Anticipated Repayment Date, if it has not previously done so, the related
borrower is required to enter into a "lockbox agreement" whereby all revenue
from the related Mortgaged Property shall be deposited directly into a
designated account controlled by the Servicer; and (iv) any cash flow from the
related Mortgaged Property that is applied to amortize such Mortgage Loan
following its Anticipated Repayment Date shall, to the extent such net cash flow
is in excess of the Monthly Payment payable therefrom, be net of budgeted and
discretionary (servicer approved) capital expenditures; and

            (lv) Except as disclosed in the Prospectus Supplement, no Mortgage
Loan, and no group of Mortgage Loans made to the same borrower and to borrowers
that are affiliates, accounted for more than 5.0% of the aggregate of the Stated
Principal Balances of all of the Mortgage Loans and the mortgage loans sold to
the Depositor by Column Financial, Inc. ("Column") pursuant to that certain
Mortgage Loan Purchase Agreement dated as of August 1, 2001 between the
Depositor and Column, as of the Cut-Off Date.

<PAGE>

                                    EXHIBIT B

                             AFFIDAVIT OF LOST NOTE

STATE OF NEW YORK       )
                        )  ss.:
COUNTY OF NEW YORK      )

                        , being duly sworn, deposes and says:

            1. that he is an authorized signatory of PNC Bank, National
Association ("PNC");

            2. that PNC is the owner and holder of a mortgage loan in the
original principal amount of $____________ secured by a mortgage (the
"Mortgage") on the premises known as ____________ located in ____________;

            3. (a) that PNC , after having conducted a diligent investigation of
its records and files, has been unable to locate the following original note and
believes that said original note has been lost, misfiled, misplaced or destroyed
due to a clerical error:

            a note in the original sum of $____________ made by ____________, to
            PNC Bank, National Association, under date of ____________ (the
            "Note");

            4. that the Note is now owned and held by PNC;

            5. that the Note has not been paid off, satisfied, assigned,
transferred, encumbered, endorsed, pledged, hypothecated, or otherwise disposed
of and that the original Note has been either lost, misfiled, misplaced or
destroyed;

            6. that no other person, firm, corporation or other entity has any
right, title, interest or claim in the Note except PNC; and

            7. upon assignment of the Note by PNC to Credit Suisse First Boston
Mortgage Securities Corp. (the "Depositor") and subsequent assignment by the
Depositor to the trustee for the benefit of the holders of the Credit Suisse
First Boston Mortgage Securities Corp. Commercial Mortgage Pass-Through
Certificates, Series 2001-CP4 (the "Trustee") (which assignment may, at the
discretion of the Depositor, be made directly by PNC to the Trustee) PNC
covenants and agrees (a) promptly to deliver to the Trustee the original Note if
it is subsequently found, and (b) to indemnify and hold harmless the Trustee and
its successors and assigns from and against any and all costs, expenses and
monetary losses arising as a result of PNC's failure to deliver said original
Note to the Trustee.

                                       PNC BANK, NATIONAL ASSOCIATION

                                       By:______________________________________
                                          Name:
                                          Title:

Sworn to before me this
day of August [__], 2001

<PAGE>

                                    EXHIBIT C

                                     FORM OF
                          ASSIGNMENT OF MORTGAGE(S) AND
                 ASSIGNMENT OF ASSIGNMENT OF LESSOR'S INTERESTS
                          IN LEASES, RENTS AND PROFITS

            KNOW ALL MEN BY THESE PRESENTS:

            THAT, as of ____________, 2001, PNC Bank, National Association, a
national banking association, whose address is [______________________________]
("ASSIGNOR") in consideration of ten and 00/100 ($10.00) dollars and other good
and valuable consideration, paid by Wells Fargo Bank Minnesota, N.A., as trustee
for Credit Suisse First Boston Mortgage Securities Corp. Commercial Mortgage
Pass-Through Certificates, Series 2001-CP4, whose address is 45 Broadway, New
York, New York 10001 ("ASSIGNEE"), receipt of which is acknowledged by ASSIGNOR,
hereby sells, assigns, transfers, sets over and conveys unto the ASSIGNEE
certain mortgage(s) and assignments of leases, rents and profits and other
collateral documents as follows:

                See Schedule "A" attached hereto and incorporated
                            herein by this reference.

            TOGETHER with the note(s), debt(s) and claim(s) secured by said
mortgage(s) and the covenants contained in said mortgage(s), together with all
amendments, supplements and modifications thereto and all liens, financing
statements, guaranties and security interests securing the payment of such
notes, including, without limitation, any other documents recorded in the real
property records of the jurisdiction in which the real property covered by the
mortgage(s) is located with respect to such notes, and any other documents,
agreements, instruments or property relating to such loan(s) and all right,
title, interest, claims, demands, causes of action and judgments securing or
relating to such loan(s); TO HAVE AND TO HOLD the same unto the ASSIGNEE and to
the successors, legal representatives and assigns of the ASSIGNEE forever.

            THIS ASSIGNMENT is made without recourse or representation or
warranty of any kind or nature, express or implied except as expressly set forth
in that certain Mortgage Loan Purchase Agreement, dated as of August 1, 2001
between ASSIGNOR and Credit Suisse First Boston Mortgage Securities Corp.

<PAGE>

            IN WITNESS WHEREOF, the ASSIGNOR has duly executed this Assignment
the __ day of ________ 2001.

IN PRESENCE OF:

[corporate seal]

                                       By:____________________________________
                                          Name:
                                          Title:

<PAGE>

STATE OF                )
                        )  ss.:
COUNTY OF               )

            On this ____ day of ____________, 2001, before me personally
appeared ______________________________________ to me known, who being by me
duly sworn, did say that he/she is the ________________________ Vice President
of _____________________, a ________________ corporation, that the seal affixed
to the foregoing instrument is the corporate seal of said corporation, that said
instrument was signed and sealed on behalf of said corporation by authority of
its Board of Directors, and acknowledged said instrument to be the free act and
deed of said corporation.

            IN WITNESS WHEREOF, I have hereunto set my hand and affixed my
notarial seal the day and year last above written.

                                        Signature_______________________________

                                        Print Name______________________________

                                  Notary Public in and for said County and State

[AFFIX SEAL]                        My Commission expires on____________________

<PAGE>

                             ASSIGNMENT OF MORTGAGE
                                       AND
                 ASSIGNMENT OF ASSIGNMENT OF LESSOR'S INTERESTS
                          IN LEASES, RENTS AND PROFITS

                         PNC BANK, NATIONAL ASSOCIATION
                                       TO
                  WELLS FARGO BANK MINNESOTA, N.A.., AS TRUSTEE

                              RECORD AND RETURN TO:

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