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                                                                  Exhibit 10.18

                                CONTRACT OF SALE

                                 by and between

                            BEST PROPERTY FUND, L.P.,
                                    as Seller

                                       and

                      PRAECIS PHARMACEUTICALS INCORPORATED,
                                  as Purchaser

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




                                    Property:

                                830 Winter Street

                             Waltham, Massachusetts

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                                TABLE OF CONTENTS

                                                                        PAGE

Property..................................................................1

Purchase Price............................................................1

Condition of Property; Title..............................................3

Time and Place of Closing.................................................4

Conditions to Closing.....................................................4

Seller's Representations and Agreements..................................12

Purchaser's Representation and Agreements................................20

Apportionments...........................................................22

Closing Matters..........................................................24

Title Examination........................................................24

Risk of Loss.............................................................26

Brokerage................................................................28

Remedies.................................................................28

Notices .................................................................29

Foreign Investment In Real Property Tax Act..............................31

Choice of Law............................................................31

Exhibit A - LEGAL DESCRIPTION OF LAND....................................39

Exhibit B - SELLER'S WORK................................................40

EXHIBIT B - PUNCH LIST ITEMS.............................................47

Exhibit C - PERMITTED TITLE EXCEPTIONS...................................48

                                        i


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Exhibit D - CONTRACTS AND AGREEMENTS.....................................49

Exhibit E - LIST OF PERMITS..............................................50

                                       ii


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                                CONTRACT OF SALE

         AGREEMENT, made on this 14th day of January, 2000, by and between BEST
PROPERTY FUND, L.P., a Delaware limited partnership, ("SELLER") and PRAECIS
PHARMACEUTICALS INCORPORATED, a Delaware corporation, ("PURCHASER").

                              W I T N E S S E T H:

         In consideration of the mutual covenants and provisions herein
contained, including without limitation Purchaser's payment to Seller of TWO
HUNDRED FIFTY THOUSAND AND 00/100 DOLLARS ($250,000.00) in the event Purchaser
terminates this Agreement pursuant to SECTION 5(c), and other good and valuable
consideration, the receipt and sufficiency of which hereby are acknowledged, the
parties hereby covenant and agree as follows:

         1. PROPERTY. Seller hereby agrees to sell and Purchaser agrees to
purchase, upon the terms and conditions set forth in this Agreement, the
property ("PROPERTY") consisting of (a) those certain plots, pieces or parcels
of land located in Waltham, Massachusetts, having a street address at 830 Winter
Street, and all more particularly described in EXHIBIT A hereto ("LAND"), (b)
all buildings and all other structures, facilities or improvements presently
located or hereafter located in or on the Land ("IMPROVEMENTS"), (c) all
fixtures, machinery, systems, equipment, warranties, guaranties, indemnities,
claims against third parties relating to the Land or Improvements, licenses,
permits, approvals, documents, plans, specifications, drawings, items of
personal property owned by Seller attached or appurtenant to, located on and
used in connection with the ownership, use, operation or maintenance of the Land
or the Improvements (collectively, the "PERSONAL PROPERTY"), and (d) all strips,
gores, easements, privileges, licenses, rights and appurtenances relating to any
of the foregoing.

         2. PURCHASE PRICE. (a) The purchase price for the Property is FORTY-ONE
MILLION FIVE HUNDRED THOUSAND 00/100 DOLLARS ($41,500,000.00) ("PURCHASE
PRICE").

         (b)      The Purchase Price shall be payable as follows:

                  (i) Upon the execution of this Agreement, ONE MILLION TWO
         HUNDRED FIFTY THOUSAND AND 00/100 DOLLARS ($1,250,000.00)

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         ("INITIAL DOWNPAYMENT"), by Purchaser's check, evidencing good funds,
         subject to collection, payable to the order of "Brown, Rudnick, Freed &
         Gesmer, P.C., as escrow agent" ("ESCROW AGENT") or by wire transfer of
         immediately available federal funds to an account or accounts to be
         designated in writing by Escrow Agent.

                  (ii) Unless on or before April 6, 2000, Purchaser has
         delivered to Seller a copy of a Financing Commitment (hereinafter
         defined), then on April 7, 2000, Purchaser shall deliver to Escrow
         Agent SEVEN HUNDRED FIFTY THOUSAND AND 00/100 DOLLARS ($750,000.00)
         ("ADDITIONAL DOWNPAYMENT") by Purchaser's check, evidencing good funds,
         subject to collection, payable to the order of Escrow Agent, or by wire
         transfer of immediately available federal funds to an account or
         accounts to be designated in writing by Escrow Agent following the
         written request of Purchaser. Notwithstanding the foregoing, Seller and
         Purchaser agree and acknowledge that Purchaser's purchase of the
         Property is not subject to, or conditioned upon, Purchaser obtaining
         financing for such purchase, including, without limitation, Purchaser
         obtaining a Financing Commitment or the ultimate funding of a Financing
         Commitment. Seller and Purchaser further agree and acknowledge that the
         provisions of this Agreement related to the Financing Commitment are
         made a part of this Agreement so as to enable Seller to evaluate
         Purchaser's ability to consummate the purchase of the Property.

                           For purposes of this Agreement, the term "FINANCING
         COMMITMENT" shall mean a bona fide commitment from an institutional
         third party lender, which is unaffiliated with Purchaser, to finance
         not less than seventy percent (70.0%) of the Purchase Price, on
         prevailing commercial terms, which, together with replacements or
         extensions thereof, shall remain in effect until the Closing
         (hereinafter defined).

                  (iii) If Purchaser terminates this Agreement pursuant to
         SECTION 5(c), then $250,000.00 of the Initial Downpayment shall be paid
         to Seller and the remainder of the Initial Downpayment, together with
         all accrued interest thereon, shall be paid to Purchaser. If Purchaser
         does not terminate this Agreement pursuant to SECTION 5(c) and the
         Closing (hereinafter defined) occurs, then the Initial Downpayment,
         together with the Additional Downpayment, if applicable, and all
         accrued interest thereon (the "INTEREST"), shall be paid by Escrow
         Agent to Seller. The Initial Downpayment, the Additional Downpayment,
         if applicable, and the Interest shall be credited against the Purchase
         Price. If Purchaser does not terminate this Agreement pursuant to
         SECTION 5(c) but the Closing does not occur, then the Initial

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         Downpayment, together with the Additional Downpayment, if applicable,
         and the Interest shall be paid by Escrow Agent in accordance with the
         terms of SECTION 13 of this Agreement. Escrow Agent shall have no
         liability in connection with the Initial Downpayment, the Additional
         Downpayment or the Interest, except for its own gross negligence or
         willful misconduct. The Initial Downpayment and the Additional
         Downpayment, if applicable, are referred to herein collectively as the
         "DOWNPAYMENT." The Downpayment shall be invested by Escrow Agent in a
         money market fund.

                  (iv) At the Closing, an amount, subject to adjustment pursuant
         to the terms of this Agreement, equal to the difference between the
         Purchase Price and the total of the amount of the Downpayment received
         by Escrow Agent plus the Interest shall be paid by good, unendorsed
         cashier's or official bank check payable to the order of Seller (or
         Seller's designee or designees) or by wire transfer of immediately
         available federal funds to an account or accounts to be designated in
         writing by Seller at or prior to the Closing.

         (c) Escrow and title insurance costs, fees and expenses shall be paid
in accordance with SECTION 9 (a) hereof.

         3. CONDITION OF PROPERTY; TITLE. (a) Subject to the terms of this
Agreement, Purchaser agrees to purchase the Property on the Closing Date (as
hereinafter defined) in its then "AS IS" condition; Seller acknowledging that
Seller is required to achieve Final Completion (as defined in EXHIBIT B) of the
Seller's Work (hereinafter defined) in accordance with the terms of EXHIBIT B.
Purchaser further agrees that from and after the Closing Seller shall not be
liable for any latent or patent defects in the Property. Except as set forth in
this Agreement, Seller has not made any repre sentations as to the physical
condition or any other matter or thing affecting or related to the Property,
and, except as set forth in EXHIBIT B hereto, Seller shall have no obligation to
improve the Property.

         (b) Purchaser shall accept title to the Property subject to the matters
set forth on EXHIBIT C hereto and any matter arising out of any action taken by
Purchaser or its agents (collectively, the "PERMITTED TITLE EXCEPTIONS"). If
Seller shall so request, Purchaser will allow Seller to pay from the balance of
the Purchase Price as much thereof as may be necessary to satisfy any lien(s) or
encumbrance(s) which Seller is obligated or elects to cure hereunder and will
provide Seller at the Closing with separate certified and/or official bank
checks or effect such additional wire transfers, payable as directed in writing
by Seller, for such purposes.

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         (c) The parties acknowledge that Seller will be constructing certain
improvements ("SELLER'S WORK") at the Property in accordance with EXHIBIT B.
Seller shall use commercially diligent efforts to complete the construction of
the Seller's Work and deliver the Property on or before September 1, 2000
("TARGET COMPLETION DATE"). If, despite such commercially diligent efforts,
Seller has been unable to complete such Seller's Work and deliver the Property
on or before the Target Completion Date, Purchaser's remedies for such failure
shall be as set forth in EXHIBIT B.

         (d) If prior to the Closing, Purchaser delivers to Seller an
environmental report from a Licensed Site Professional concluding that there is
a reasonable likelihood that the environmental condition of the Property is
adversely different than it was on the date of this Agreement, then Seller
either shall remediate such condition, and deliver reasonable evidence thereof
to Purchaser, or deliver to Purchaser reasonably acceptable evidence that the
environmental condition of Property is not adversely different than it was on
the date of this Agreement.

         4. TIME AND PLACE OF CLOSING. (a) The closing of the transactions
contemplated hereby ("CLOSING") shall take place at 10:00 a.m. on the fifteenth
(15th) Business Day (hereinafter defined) after Seller notifies Purchaser
("CLOSING NOTICE") of the Final Completion of Seller's Work or on such other
date as may be permitted by the terms of this Agreement ("CLOSING DATE"). If the
Final Completion of the Seller's Work does not occur by December 31, 2000 (as
such date shall be extended by the number of days that Final Completion of the
Seller's Work was delayed because of Purchaser Initiated Change Orders), then
Purchaser may terminate this Agreement by written notice to Seller, given no
later than five (5) Business Days after such date, whereupon the Downpayment,
plus the Interest, shall be paid to Purchaser. As used herein, the term
"BUSINESS DAY" shall mean any day other than a Saturday, Sunday or national
holiday. The Closing shall take place at the offices of Brown, Rudnick, Freed &
Gesmer, One Financial Center, 18th Floor, Boston, Massachusetts 02111, or at
such time and place to which Seller and Purchaser may mutually agree.

         5. CONDITIONS TO CLOSING. (a) PURCHASER'S CONDITIONS. Purchaser's
obligation to pay the Purchase Price, to accept title to the Property and
otherwise to consummate the transactions contemplated hereby shall be subject
to the satisfaction of the following conditions precedent on and as of the
Closing Date:

                  (i) Seller shall deliver to Purchaser on or before the Closing
Date the following documents ("SELLER'S CLOSING DOCUMENTS"):

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                           (1)      a quitclaim deed ("DEED") conveying Seller's
                                    fee simple interest in the Land and the
                                    Improvements to Purchaser (which fee simple
                                    interest shall be the same fee simple
                                    interest Seller had in the Land and the
                                    Improvements on January 3, 2000, subject to
                                    the Permitted Title Exceptions) in proper
                                    statutory form for recording, duly executed
                                    and acknowledged by Seller;

                           (2)      a bill of sale, conveying Seller's right,
                                    title and interest in the Personal Property
                                    to Purchaser, free of any liens and
                                    encumbrances, in form and substance
                                    reasonably acceptable to Seller and
                                    Purchaser ("BILL OF SALE"), duly executed
                                    and acknowledged by Seller;

                           (3)      an assignment by Seller and assumption by
                                    Purchaser, in form and substance reasonably
                                    acceptable to Seller and Purchaser ("GENERAL
                                    ASSIGNMENT"), duly executed and acknowledged
                                    by Seller and by Purchaser, of all of
                                    Seller's (or Bren Schreiber Properties,
                                    Inc.'s or Seller's agent's) obligations,
                                    right, title and interest in, to and under:

                                    (A)      the contracts and agreements and
                                             the amendments, modifications and
                                             supplements thereto set forth on
                                             EXHIBIT D attached hereto
                                             (collectively, "CONTRACTS");

                                    (B)      the Permits (as defined in SECTION
                                             5(a)(i)(5) hereof);

                                    (C)      (x) all guaranties and warranties
                                             arising under the Construction
                                             Contract (as defined in EXHIBIT B)
                                             as it exists on the date hereof;
                                             (y) all guaranties and warranties
                                             arising under the Design Contract
                                             (as defined in EXHIBIT B) as it
                                             exists on the date hereof and (z)
                                             all other guaranties and
                                             warranties then in effect with
                                             respect to the Improvements and the
                                             Personal Property (collectively,
                                             the "GUARANTIES"); and

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                                    (D)      All existing claims and recourse of
                                             any nature whatsoever benefiting
                                             Seller and arising under the
                                             Contracts and/or the Guaranties.

                                    Notwithstanding the foregoing, with respect
                                    to that certain Mutual Covenants agreement
                                    dated March 25, 1999 between Seller and
                                    Polaroid Corporation, filed with the South
                                    Registry District of Middlesex County as
                                    Document No. 1101667 ("MUTUAL COVENANTS"),
                                    which is one of the Contracts, the General
                                    Assignment shall provide: (v) that at the
                                    Closing, Purchaser shall deliver to Polaroid
                                    bonds with respect to the water pipeline and
                                    traffic signalization matters described in
                                    the Mutual Covenants (which bonds shall be
                                    in the amount equal to the remaining
                                    obligations of Seller with respect to such
                                    matters, which shall not exceed $150,000 as
                                    to each such matter) in replacement of the
                                    bonds which were delivered under the Mutual
                                    Covenants by Seller (or otherwise make
                                    arrangements, reasonably acceptable to
                                    Seller, for the release of such bonds), (w)
                                    that Seller and Purchaser shall cooperate to
                                    obtain the release by Polaroid Corporation
                                    of the bonds which were so delivered by
                                    Seller, (x) that Purchaser shall assume all
                                    obligations of Seller set forth in the
                                    Mutual Covenants with respect to traffic
                                    signalization under the Mutual Covenants,
                                    (y) that if Seller has expended any funds
                                    which were credited or are creditable
                                    against Seller's obligations with respect to
                                    traffic signalization under the Mutual
                                    Covenants, then at the Closing, Purchaser
                                    shall reimburse Seller for the amounts so
                                    expended by Seller, and (z) that if as of
                                    the Closing, Seller has not satisfied its
                                    obligations under the Mutual Covenants with
                                    respect to the water pipeline, as evidenced
                                    by an acknowledgement of satisfaction
                                    executed by Polaroid Corporation, or its
                                    successors), Purchaser will assume such
                                    obligations but Seller will pay to
                                    Purchaser, at the Closing, an amount equal
                                    to the difference between $150,000.00 and
                                    the amount of any funds expended by Seller
                                    which were credited or are creditable
                                    against Seller's obligations with respect to
                                    said water pipeline;

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                           (4)      to the extent the same are in Seller's
                                    possession, original, fully executed copies
                                    of the Contracts, and originals, certified
                                    by Seller, as correct and complete, of the
                                    Construction Contract and the Design
                                    Contract;

                           (5)      Original mechanical, electrical and plumbing
                                    plans and specifications (together with
                                    as-built plans therefor prepared by the
                                    subcontractors performing such work),
                                    surveys, fire underwriter certificates for
                                    the Property, and other certificates,
                                    licenses and permits for the Property
                                    (including all amendments, modifications,
                                    supplements and extensions thereof)
                                    ("PERMITS"), except to the extent the same
                                    are required to be, and are, affixed at the
                                    Property;

                           (6)      Originals of all Guaranties (other than
                                    those guaranties and warranties set forth in
                                    the Construction Contract or the Design
                                    Contract which are otherwise assigned to
                                    Purchaser) and a full copy of the Record
                                    Drawings (as defined in EXHIBIT B) certified
                                    by Architect (as defined in EXHIBIT B) to be
                                    correct and complete;

                           (7)      a certificate of Seller dated as of the
                                    Closing Date, to the effect that (A) this
                                    Agreement and Seller's Closing Documents
                                    executed by Seller have been duly
                                    authorized, executed and delivered by Seller
                                    pursuant to all necessary resolutions or
                                    consents of the general partner of Seller
                                    and that said resolutions or consents remain
                                    in full force and effect, (B) appearing on
                                    said certificate is the signature of persons
                                    authorized to act on behalf of Seller's
                                    general partner who have executed this
                                    Agreement and who will execute all
                                    agreements to be delivered by Seller
                                    hereunder; (C) the executing persons acting
                                    on behalf of Seller's general partner are
                                    fully authorized to act on behalf of
                                    Seller's general partner and that such
                                    general partner is fully authorized to act
                                    on behalf of Seller and (D) Seller's
                                    representations set forth in this Agreement
                                    remain true as of the Closing, or if not
                                    true, the specific manner in which they are
                                    not true;

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                           (8)      a letter by Seller to the other parties to
                                    the Contracts, the Construction Contract and
                                    the Design Contract informing them of the
                                    change in ownership of the Property;

                           (9)      an affidavit, duly executed and acknowledged
                                    by Seller, in the standard form required by
                                    the Title Company (as hereinafter defined),
                                    relative to mechanics liens and parties in
                                    possession;

                           (10)     Certificates for the benefit of Seller and
                                    Purchaser from the Architect and the
                                    contractor under the Construction Contract
                                    stating that all sums due under said
                                    agreements have been paid in full by Seller
                                    and that Seller has completely performed its
                                    obligations thereunder; and

                           (11)     Such certificates of legal existence and
                                    corporate good standing and affidavits of
                                    Seller, Seller's general partner and
                                    Schreiber Developments, LLC as the Title
                                    Company reasonably may request; provided
                                    that such certificates do not materially
                                    increase Seller's liability under this
                                    Agreement.

                  (ii) Subject to SECTION 6(e) hereof, the representations and
         warranties of Seller contained in this Agreement shall be true and
         complete in all material respects at and as of the Closing Date as if
         such representations and warranties were made at and as of the Closing
         Date and Seller shall have performed and complied with, in all material
         respects, all covenants, agreements, conditions, terms and provisions
         of this Agreement required to be performed or complied with by Seller
         prior to or at the Closing, in each case subject only to exceptions
         permitted by this Agreement.

                  (iii) Seller shall have Finally Completed Seller's Work.

                  (iv) The environmental condition of the Property shall not be
         adversely different than it is in on the date of this Agreement,
         subject to Seller's right to remediate pursuant to SECTION 3(d).

                                        8

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         (b) SELLER'S CONDITIONS. Seller's obligation to deliver title to the
Property and otherwise to consummate the transactions contemplated hereby shall
be subject to compliance by Purchaser with the following conditions precedent on
and as of the Closing Date:

                  (i) Purchaser shall deliver to Seller on the Closing Date the
         balance of the Purchase Price due pursuant to SECTION 2(b) hereof and
         such other amounts as are due Seller hereunder, subject to adjustment
         of such amount pursuant to SECTION 8 hereof;

                  (ii) Purchaser shall deliver to Seller on the Closing Date the
         following, each of which shall be in form and substance reasonably
         satisfactory to Seller ("PURCHASER'S CLOSING DOCUMENTS"):

                           (1)      a certificate of Purchaser, dated the
                                    Closing Date, to the effect that (A) this
                                    Agreement and Purchaser's Closing Documents
                                    executed by Purchaser have been duly
                                    authorized, executed and delivered by
                                    Purchaser pursuant to all necessary
                                    resolutions or consents of the Board of
                                    Directors of Purchaser, and that said
                                    resolutions and consents remain in full
                                    force and effect, (B) appearing on said
                                    certificate is the true signature of the
                                    officer or officers of Purchaser who have
                                    executed this Agreement and who will execute
                                    all agreements and instruments to be
                                    delivered by Purchaser hereunder, (C) the
                                    executing officer or officers of Purchaser
                                    are fully authorized to act on behalf of
                                    Purchaser and (D) Purchaser's
                                    representations set forth in this Agreement
                                    remain true as of the Closing, or if not
                                    true, the specific manner in which they are
                                    not true;

                           (2)      duly executed and acknowledged counterparts
                                    of the General Assignment described in
                                    SECTION 5(a)(i)(3) hereof; and

                           (3)      sufficient funds to the Title Company to
                                    satisfy all amounts payable by Purchaser
                                    under SECTION 9(a)(i) hereof;

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                  (iii) Purchaser shall, at the reasonable request of Seller,
         from time to time after April 7, 2000, furnish to Seller updated
         financial information regarding Purchaser.

                  (iv) The representations and warranties of Purchaser contained
         in this Agreement shall be true and complete in all material respects
         at and as of the Closing Date as if such representations and warranties
         were made at and as of the Closing Date and Purchaser shall have
         performed and complied with, in all material respects, all covenants,
         agreements, conditions, terms and provisions of this Agreement required
         to be performed or complied with by Purchaser prior to or at the
         Closing, in each case subject only to exceptions permitted by this
         Agreement.

         (c) DUE DILIGENCE PERIOD. (i) Purchaser has commenced its due diligence
review ("DUE DILIGENCE REVIEW"), which shall include, without limitation, the
matters listed in (1), (2) and (3) of this SECTION 5(c)(i), on the date of this
Agreement. Purchaser shall complete the Due Diligence Review no later than
February 7, 2000 (the "DUE DILIGENCE PERIOD"). During the Due Diligence Period,
Seller shall:

                  (1)      cooperate in providing Purchaser and its
                           representatives, agents and designees with access to
                           the Property at reasonable times, upon reasonable
                           prior notice and, to conduct, at Purchaser's sole
                           cost and expense, such physical, economic,
                           environmental, pest control and other investigations
                           and such other tests and studies as Purchaser may
                           elect to perform with respect to the Property;
                           provided, however, that Purchaser shall not conduct
                           any so-called "Phase II" environmental investigation
                           at the Property without the prior written consent of
                           Seller, which consent may be granted, withheld or
                           conditionally granted, in Seller's sole discretion;

                  (2)      deliver to Purchaser correct and complete copies of
                           all contracts affecting the Property in Seller's
                           possession or control; and

                  (3)      deliver to Purchaser correct and complete copies of
                           the following written materials pertaining to the
                           Property, to the extent the same are in Seller's
                           possession or control and to the extent Seller has
                           not provided such materials to Purchaser prior to the
                           date of this Agreement:

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                           (A)      a survey and existing title report with
                                    respect to the Property;

                           (B)      copies of the tax bills for the Property;

                           (C)      all existing drawings, plans and
                                    specifications and contracts relating to
                                    Seller's Work;

                           (D)      all existing building permits relating to
                                    the Property; and

                           (E)      any other existing written contracts that
                                    would be binding on Purchaser following the
                                    Closing.

                  (ii) If Purchaser is unsatisfied, in Purchaser's sole and
         absolute discretion, with the results of the Due Diligence Review or
         any other matter regarding the Property, Purchaser may terminate this
         Agreement by so notifying Seller on or before the last day of the Due
         Diligence Period. If Purchaser so notifies Seller, this Agreement shall
         terminate and $1,000,000.00 of the Downpayment, plus the Interest,
         shall be returned to Purchaser, and the remainder of the Downpayment,
         $250,000.00, shall be released to Seller in consideration for Seller
         entering into this Agreement. In the event that Purchaser does not so
         notify Seller, this Agreement shall continue in full force and effect.

                  (iii) Intentionally omitted.

                  (iv) Purchaser shall repair and/or replace any property
         damaged at the Property to the same condition and quality as existed
         prior to such damage if such damage is caused by or arises out of or in
         connection with the Due Diligence Review. Purchaser shall indemnify
         Seller against any liability and damages, including, without
         limitation, any damage, death or injury to any person or property which
         occurs as a result of the negligence or misconduct of Purchaser or its
         agents in connection with the Due Diligence Review; provided, however,
         that Purchaser shall have no liability resulting from the mere
         discovery of existing conditions at or affecting the Property.

                  (v) Purchaser acknowledges and agrees that if as a result of
         the Due Diligence Review, Purchaser or its agents have actual knowledge
         of any matter or state of facts inconsistent with the Information
         (hereinafter defined) or the representations and warranties of Seller
         set forth in this Agreement

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         then the Information and the representations and warranties of Seller
         set forth in this Agreement shall be deemed modified to conform to the
         matters and state of facts actually known by Purchaser or its agents as
         a result of the Due Diligence Review.

                  (vi) The information and data (collectively, "INFORMATION")
         which has been or will be made available to Purchaser with respect to
         the Property in connection with the Due Diligence Review is
         confidential and shall be governed by the terms of that certain
         Confidentiality Agreement dated as of December 23, 1999 between Seller
         and Purchaser ("CONFIDENTIALITY AGREEMENT"). In the event that this
         Agreement is terminated pursuant to the provisions of this SECTION
         5(c), all written Information shall be returned promptly to Seller.

                  (vii) The provisions of SECTIONS 5(c)(iv) AND 5(c)(vi) shall
         survive the Closing or earlier termination of this Agreement, as the
         case may be.

         (d) CONDITIONS GENERALLY. The foregoing conditions are for the benefit
only of the party for whom they are specified to be conditions precedent and
such party may, in its sole discretion, waive any or all of such conditions and
close title under this Agreement without any increase in, abatement of or credit
against the Purchase Price.

         6.  SELLER'S REPRESENTATIONS AND AGREEMENTS

         (a) REPRESENTATIONS. Seller represents and warrants to Purchaser as
follows (for purposes of this SECTION 6(a), Seller's knowledge shall be deemed
to be the actual knowledge of David S. Hall, without any independent
investigation):

                  (i)      AS TO SELLER'S ORGANIZATION, POWER AND AUTHORITY.

                           (1)      Seller is a limited partnership that has
                                    been duly organized and is validly existing
                                    under the laws of the State of Delaware and
                                    as of the Closing shall be duly qualified
                                    to do business in the Commonwealth of
                                    Massachusetts;

                           (2)      Seller has full power and right to enter
                                    into and perform its obligations under this
                                    Agreement and the other agreements
                                    contemplated herein to be executed and

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                                    performed by it, including, without being
                                    limited to, conveying the Property as herein
                                    provided;

                           (3)      Neither Seller nor any general partner in
                                    Seller is in the hands of a receiver, nor is
                                    an application for a receiver pending, nor
                                    has Seller or any general partner in Seller
                                    made an assignment for the benefit of
                                    creditors, nor has Seller or any general
                                    partner in Seller filed, or had filed
                                    against it, any petition in bankruptcy;

                           (4)      The execution and delivery of this Agreement
                                    and the consummation of the transactions
                                    contemplated hereby on the part of Seller
                                    (A) have been duly authorized by all
                                    necessary partnership acts on the part of
                                    Seller and any general partner in Seller,
                                    and (B) do not and will not (v) require any
                                    governmental or other consent, (w) violate
                                    or conflict with any judgment, decree or
                                    order of any court applicable to or
                                    affecting Seller or any general partner in
                                    Seller, (x) violate or conflict with any law
                                    or governmental regulation applicable to
                                    Seller or any general partner in Seller, (y)
                                    violate or conflict with the organizational
                                    documents of Seller or any general partner
                                    in Seller and (z) do not and will not result
                                    in the breach of, or constitute a default
                                    under, any agreement, contract, indenture or
                                    other instrument or other obligation to
                                    which Seller is a party or is otherwise
                                    bound. Upon the assumption that this
                                    Agreement constitutes the legal, valid and
                                    binding obligation of Purchaser, this
                                    Agreement constitutes the legal, valid and
                                    binding obligation of Seller;

                           (5)      Seller is not a "foreign person", as defined
                                    in Section 1445 of the United States
                                    Internal Revenue Code of 1986, as amended,
                                    and the regulations issued thereunder
                                    ("CODE"); and

                           (6)      There are no actions, suits or proceedings
                                    (including, but not limited to bankruptcy)
                                    pending or, to the knowledge of Seller,
                                    threatened, against Seller or, to Seller's
                                    knowledge, affecting Seller which if
                                    determined adversely to Seller, would
                                    adversely affect the

                                       13

<PAGE>



                                    Property or Seller's ability to perform its
                                    obligations hereunder.

                  (ii)     AS TO THE PROPERTY.

                           (1)      Prior to the date of this Agreement, Seller
                                    has not received written notice of any
                                    pending or threatened condemnation of all or
                                    any part of the Property;

                           (2)      Except as set forth in the Permitted Title
                                    Exceptions, there are no occupancy rights,
                                    leases or tenancies presently affecting the
                                    Property;

                           (3)      (A) The Contracts are all of the material
                                    service, maintenance, supply and management
                                    contracts and agreements presently
                                    affecting the Property to which Seller is a
                                    party and which will be binding on Purchaser
                                    or the Property following the Closing and
                                    there are no other contracts which will be
                                    binding on Purchaser or the Property
                                    following the Closing; (B) Seller has
                                    heretofore delivered to Purchaser true and
                                    complete copies of each of the Contracts;
                                    and (C) the Contracts have not been modified
                                    or amended, except as indicated on EXHIBIT
                                    D hereto;

                           (4)      Seller's obligation to Polaroid Corporation
                                    and any other parties under the Mutual
                                    Covenants with respect to the water pipeline
                                    described therein shall not exceed
                                    $150,000.00 in the aggregate and with
                                    respect to traffic signalization described
                                    therein shall not exceed $150,000 in the
                                    aggregate;

                           (5)      Seller has no knowledge of any legal action
                                    commenced or threatened against Seller or
                                    Seller's interest in the Property which
                                    could materially and adversely affect the
                                    Property;

                           (6)      Seller has not received any written notice
                                    of any violation of any zoning, building,
                                    subdivision, land sales, securities, land
                                    use, ecology or environmental protection
                                    laws, ordinances, rules and regulations of
                                    govern-

                                       14

<PAGE>

                                    ment authorities including those of any and
                                    all regulatory agencies and administrative
                                    officials having or asserting jurisdiction
                                    over the Property or any portion of the
                                    Property, pertaining to the Property or any
                                    portion of the Property which has not been
                                    complied with, nor does Seller have any
                                    knowledge of any violation thereof. Seller
                                    has received no written notice prior to the
                                    date of this Agreement from any governmental
                                    authority of, nor has any knowledge of, any
                                    proposed or pending proceeding to change or
                                    redefine the zoning classification of all or
                                    any portion of the Property;

                           (7)      Seller has not received any written notice
                                    from any insurance company insuring the
                                    Property of any defects or inadequacies in
                                    the Property or any part thereof which would
                                    materially adversely affect the insurability
                                    of the Property or the premiums for the
                                    insurance thereof;

                           (8)      Seller has not received any written notice
                                    prior to the date of this Agreement from any
                                    governmental agency or official to the
                                    effect that any condemnation proceeding is
                                    contemplated in connection with the
                                    Property;

                           (9)      Intentionally omitted;

                           (10)     Except as set forth in the Permitted Title
                                    Exceptions, Seller has not granted, nor does
                                    Seller have knowledge of, any option
                                    agreements or rights of first refusal with
                                    respect to the purchase, lease or occupancy
                                    of the Property or any rights in favor of
                                    third persons to purchase or otherwise
                                    acquire the Property or any interest in the
                                    Property;

                           (11)     Seller has delivered to Purchaser true and
                                    complete copies of all Contracts (including
                                    all amendments or supplements thereto) and,
                                    to the best of Seller's knowledge, all
                                    other contracts and agreements which affect
                                    the use or operation of the Property. Seller
                                    has not received any written notice of any
                                    default under any Contract that has not been
                                    cured or waived;

                                       15

<PAGE>



                           (12)     There are no employment contracts entered
                                    into by Seller which will be binding after
                                    Closing on Purchaser as owner of the
                                    Property. Seller has no employees with
                                    respect to whom Purchaser shall bear any
                                    responsibility or continued employment
                                    after Closing or for payment of wages,
                                    benefits or the like which accrue prior to
                                    Closing;

                           (13)     As of the Closing, all contractors,
                                    subcontractors, suppliers, architects,
                                    engineers and others who have performed
                                    services, labor or supplied material during
                                    the period of Seller's ownership of the
                                    Property shall have been paid in full, and
                                    all liens arising therefrom (or claims which
                                    with the passage of time or notice or both,
                                    could mature into liens) shall have been
                                    bonded over or satisfied and released;

                           (14)     Except for the Permits, Seller has not
                                    entered into any unrecorded commitments or
                                    agreements with any governmental agencies
                                    or authorities affecting the Property;

                           (15)     To Seller's knowledge, as of the date of
                                    this Agreement, no abatement proceedings are
                                    pending with reference to any real estate
                                    taxes assessed against the Property and
                                    Seller shall not institute any such
                                    proceeding without Purchaser's prior written
                                    consent. As of the date of this Agreement,
                                    there are no betterment assessments or other
                                    special assessments presently pending or, to
                                    Seller's knowledge, proposed by any
                                    governmental authority with respect to any
                                    portion of the Property; and

                           (16)     EXHIBIT E lists all licenses, permits,
                                    authorizations, consents and approvals from
                                    any governmental authorities received by
                                    Seller in connection with the Property as of
                                    the date of this Agreement, which EXHIBIT E
                                    shall be updated at the Closing.

         (b) MISCELLANEOUS AGREEMENTS. Seller, during the term of this
Agreement, (i) will not, without Purchaser's consent, which consent Purchaser
agrees not to

                                       16

<PAGE>



unreasonably withhold or delay unless the same shall materially affect
Purchaser's rights or interests, extend or otherwise modify any Contract, (ii)
will not lease or sublease any of the Property, and (iii) will not commit to,
enter into or make any brokerage agreement related to the Property without
Purchaser's consent.

         (c) ACCESS. Purchaser or Purchaser's representative may attend all job
meetings for Seller's Work. Purchaser may, upon reasonable notice, inspect all
of Seller's records regarding Seller's Work. Seller shall, during normal
business hours upon reasonable prior notice, allow Purchaser or its
representatives access to the Property, so long as Purchaser and Purchaser's
representatives do not unreasonably interfere with the operation of the Property
or the construction activities being performed at the Property; PROVIDED,
HOWEVER, that Purchaser will indemnify Seller against any liability or damages
in connection with or arising out of any negligent or improper act of Purchaser
or its representatives as a result of their access or inspection of the
Property. Said indemnification provisions shall survive the Closing or earlier
termination of this Agreement, as the case may be.

         (d) SURVIVAL. The only representations, warranties and agreements of
Seller hereunder that shall survive the Closing are those specifically stated
herein to survive. The representations and warranties of Seller contained in
SECTION 6(A) shall survive the Closing for a period of one (1) year.

         (e) CERTAIN LIMITATIONS ON SELLER'S REPRESENTATIONS AND WARRANTIES. The
representations and warranties of Seller set forth in SECTION 6(a) are subject
to the following express limitations:

                  (i) Seller does not represent or warrant that the parties,
         other than Seller, to the Contracts, will not be in default under their
         respective Contracts.

         (f) NO OTHER REPRESENTATIONS OR WARRANTIES. Purchaser represents,
warrants and agrees that (i) as of the expiration of the Due Diligence Period
Purchaser shall have examined the Property and be familiar with the physical
condition thereof and shall have conducted such investigation of the affairs of
the Property as Purchaser has considered appropriate, (ii) neither Seller nor
any of the employees, agents or attorneys of Seller have made any verbal or
written representations, warranties, promises or guaranties whatsoever to
Purchaser, whether express or implied, and, in particular, that no such
representations, warranties, promises or guaranties have been made with respect
to the physical condition or operation of the Property, the actual or projected
revenue and expenses of the Property, the zoning and other laws, regulations and
rules applicable to the Property or the compliance of

                                       17

<PAGE>



the Property therewith, the quantity, quality or condition of the articles of
personal property and fixtures included in the transactions contemplated hereby,
the use or occupancy of the Property or any part thereof or any other matter or
thing affecting or related to the Property or the transactions contemplated
hereby, except as, and solely to the extent, herein specifically set forth, and
(iii) Purchaser has not relied upon any such representations, warranties,
promises or guaranties (other than those expressly set forth in this Agreement)
or upon any statements made in any informational brochure with respect to the
Property and has entered into this Agreement knowing that it must rely solely on
its own independent investigation, inspection, analysis, appraisal, examination
and evaluation of the facts and circumstances. `

TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, AND EXCEPT FOR SELLER'S
REPRESENTATIONS AND WARRANTIES IN SECTION 6(a), OR CONTAINED IN ANY OF TITLE
CLOSING DOCUMENTS REQUIRED TO BE DELIVERED BY SELLER AT THE CLOSING PURSUANT TO
THIS AGREEMENT (COLLECTIVELY, "SELLER'S WARRANTIES"), THIS SALE IS MADE AND WILL
BE MADE WITHOUT REPRESENTATION OR WARRANTY OF ANY KIND (WHETHER EXPRESS,
IMPLIED, OR, TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, STATUTORY) BY
SELLER. AS A MATERIAL PART OF THE CONSIDERATION OF THIS AGREEMENT, BUT WITHOUT
LIMITING SELLER'S OBLIGATION TO ACHIEVE FINAL COMPLETION OF THE SELLER'S WORK IN
ACCORDANCE WITH EXHIBIT B OR THE SATISFACTION OF THE PURCHASER'S CONDITIONS SET
FORTH IN SECTION 5(a) OR SELLER'S OBLIGATIONS UNDER SECTION 10, PURCHASER AGREES
TO ACCEPT THE PROPERTY ON AN "AS IS" AND "WHERE IS" BASIS, WITH ALL FAULTS, AND
WITHOUT ANY REPRESENTATION OR WARRANTY BY SELLER OR ANYONE ACTING OR CLAIMING
TO ACT BY, THROUGH OR UNDER OR ON SELLER'S BEHALF, ALL OF WHICH SELLER HEREBY
DISCLAIMS, EXCEPT FOR SELLER'S WARRANTIES. EXCEPT FOR SELLER'S WARRANTIES, NO
WARRANTY OR REPRESENTATION IS MADE BY SELLER AS TO FITNESS FOR ANY PARTICULAR
PURPOSE, MERCHANTABILITY, DESIGN, QUALITY, CONDITION, OPERATION OR INCOME,
COMPLIANCE WITH DRAWINGS OR SPECIFICATIONS, ABSENCE OF DEFECTS, ABSENCE OF
HAZARDOUS OR TOXIC SUBSTANCES, ABSENCE OF FAULTS, FLOODING OR COMPLIANCE WITH
LAWS AND REGULATIONS INCLUDING, WITHOUT LIMITATION, THOSE RELATING TO HEALTH,
SAFETY AND THE ENVIRONMENT (INCLUDING, WITHOUT LIMITATION, THE AMERICANS WITH
DISABILITY ACT AND COMPARABLE STATE LAWS). PURCHASER ACKNOWLEDGES THAT PURCHASER
HAS ENTERED INTO THIS AGREEMENT WITH THE INTENTION OF MAKING AND RELYING

                                       18

<PAGE>



UPON ITS OWN INVESTIGATION OF THE PHYSICAL, ENVIRONMENTAL, ECONOMIC USE,
COMPLIANCE AND LEGAL CONDITION OF THE PROPERTY, SELLER'S WARRANTIES AND THE
COVENANTS TO BE PERFORMED BY SELLER PRIOR TO THE CLOSING AS EXPRESSLY SET FORTH
IN THIS AGREEMENT, AND THAT PURCHASER IS NOT NOW RELYING, AND WILL NOT LATER
RELY, UPON ANY REPRESENTATIONS AND WARRANTIES MADE BY SELLER OR ANYONE ACTING OR
CLAIMING TO ACT, BY, THROUGH OR UNDER OR ON SELLER'S BEHALF CONCERNING THE
PROPERTY, EXCEPT FOR SELLER'S WARRANTIES AND THE CLOSING DOCUMENTS REQUIRED TO
BE DELIVERED BY SELLER AT THE CLOSING PURSUANT TO THIS AGREEMENT. ADDITIONALLY,
PURCHASER AND SELLER HEREBY AGREE THAT EXCEPT FOR SELLER'S WARRANTIES, THE
COVENANTS TO BE PERFORMED BY SELLER PRIOR TO THE CLOSING AS EXPRESSLY SET FORTH
IN THIS AGREEMENT, THE SATISFACTION OF THE PURCHASER'S CONDITIONS TO THE CLOSING
SET FORTH IN SECTION 5(a), (1) PURCHASER IS TAKING THE PROPERTY "AS IS" WITH ALL
LATENT AND PATENT DEFECTS AND THERE IS NO WARRANTY BY SELLER THAT THE PROPERTY
IS FIT FOR A PARTICULAR PURPOSE, (2) PURCHASER IS SOLELY RELYING UPON ITS
EXAMINATION OF THE PROPERTY, AND (3) PURCHASER TAKES THE PROPERTY UNDER THIS
AGREEMENT UNDER THE EXPRESS UNDERSTANDING THAT THERE ARE NO EXPRESS OR IMPLIED
WARRANTIES BY SELLER OR ANYONE ACTING OR CLAIMING TO ACT BY, THROUGH OR UNDER OR
ON SELLER'S BEHALF. FOR PURPOSES OF THIS PARAGRAPH, THE CONSTRUCTION, DESIGN AND
ENGINEERING PROFESSIONALS PERFORMING THE SELLER'S WORK SHALL NOT BE DEEMED TO BE
ACTING OR CLAIMING TO ACT BY, THROUGH OR UNDER OR ON SELLER'S BEHALF

WITH RESPECT TO THE FOLLOWING, PURCHASER FURTHER ACKNOWLEDGES AND AGREES THAT,
EXCEPT AS SET FORTH IN THE SELLER WARRANTIES, SELLER SHALL NOT HAVE ANY
LIABILITY, OBLIGATION OR RESPONSIBILITY OF ANY KIND AND THAT SELLER HAS MADE NO
REPRESENTATIONS OR WARRANTIES OF ANY KIND.

A.       THE CONTENT OR ACCURACY OF ANY REPORT, STUDY, OPINION OR CONCLUSION OF
         ANY SOILS, TOXIC, ENVIRONMENTAL OR OTHER ENGINEER OR OTHER PERSON OR
         ENTITY WHO HAS EXAMINED THE PROPERTY OR ANY ASPECT THEREOF;

                                       19

<PAGE>



B.       THE CONTENT OR ACCURACY OF ANY OF THE ITEMS (INCLUDING, WITHOUT
         LIMITATION, THE PROPERTY INFORMATION) DELIVERED TO PURCHASER PURSUANT
         TO PURCHASER'S REVIEW OF THE CONDITION OF THE PROPERTY; OR

C.       THE CONTENT OR ACCURACY OF ANY PROJECTION, FINANCIAL OR MARKETING
         ANALYSIS OR OTHER INFORMATION GIVEN TO PURCHASER BY SELLER OR REVIEWED
         BY PURCHASER WITH RESPECT TO THE PROPERTY.

D.       PURCHASER HAS RECEIVED THE ADVICE OF SOPHISTICATED REAL ESTATE
         PROFESSIONALS IN CONNECTION WITH THE TRANSACTION CONTEMPLATED BY THIS
         AGREEMENT AND IS, OR AS OF THE CLOSING, WILL BE, FAMILIAR WITH THE
         PROPERTY AND ITS SUITABILITY FOR PURCHASER'S INTENDED USE. THE
         PROVISIONS OF THIS SECTION 6(f) SHALL SURVIVE INDEFINITELY ANY CLOSING
         OR TERMINATION OF THIS AGREEMENT AND SHALL NOT BE MERGED INTO THE
         DOCUMENTS EXECUTED AT THE CLOSING.

         7.  PURCHASER'S REPRESENTATION AND AGREEMENTS.

         (a) REPRESENTATIONS. Purchaser represents, warrants and covenants with
Seller as follows:

                  (i) Purchaser is a corporation that has been duly organized
         and is validly existing under the laws of Delaware and is duly
         qualified to do business in the Commonwealth of Massachusetts;

                  (ii) Purchaser has full power and right to enter into and
         perform its obligations under this Agreement and the other agreements
         contemplated herein to be executed and performed by it;

                  (iii) Purchaser is not in the hands of a receiver, nor is
         application for a receiver pending, nor has Purchaser made an
         assignment for the benefit of creditors, nor has Purchaser filed, or
         had filed against it, any petition in bankruptcy; and

                  (iv) The execution and delivery of this Agreement and the
         consummation of the transactions contemplated hereby on the part of
         Purchaser (1) have been duly authorized by all necessary corporate acts
         on the part of

                                       20

<PAGE>



         Purchaser, and (2) do not and will not (A) require any governmental or
         other consent, (B) violate or conflict with any judgment, decree or
         order of any court applicable to or affecting Purchaser, (C) violate or
         conflict with any law or governmental regulation applicable to
         Purchaser, (D) violate or conflict with the organization documents of
         Purchaser and (E) do not and will not result in the breach of, or
         constitute a default under, any agreement, contract, indenture or other
         instrument or other obligation to which Purchaser is a party or is
         otherwise bound. Upon the assumption that this Agreement constitutes
         the legal, valid and binding obligation of Seller, this Agreement
         constitutes the legal, valid and binding obligation of Purchaser.

         (b) MISCELLANEOUS AGREEMENTS. In the event the Closing does not occur
and this Agreement is terminated, Purchaser shall promptly return to Seller all
copies of Information without retaining any copy thereof or extract therefrom.

         (c) ERISA. Purchaser is not purchasing any of the Property with "plan
assets" of an Employee Benefit Plan subject to Title 1 of the Employee
Retirement Income Security Act of 1974 (as amended from time to time, the "ACT,"
and together with any regulation, rule or judicial or administrative case, order
or pronouncement arising under or connected with the Act, "ERISA") or of a plan
subject to Section 4975 of the Code. Purchaser shall take all actions reasonably
requested by Seller for the purpose of ensuring, to Seller's satisfaction, that
the transactions contemplated herein will comply with ERISA and not result in an
imposition of an excise tax under Section 4975 of the Code; such actions shall
include, without limitation, the making of such further representations and
warranties as Seller's counsel reasonably deems necessary to ensure that neither
this Agreement not any of the transactions contemplated herein will violate
ERISA or result in the imposition of an excise tax under Section 4975 of the
Code.

         (d) SURVIVAL. The representations, warranties and covenants set forth
in SECTION 7, as applicable at the Closing Date, shall survive the Closing for a
period of one (1) year.

         8. APPORTIONMENTS. (a) The following items shall be apportioned at the
Closing as of the midnight on the day immediately preceding the Closing Date:

                  (i) Real estate taxes, assessments, other than special
         assessments made against the Property, based on the rates and assessed
         valuation applicable in the fiscal year for which assessed;

                  (ii) Water rates and charges;

                                       21

<PAGE>



                  (iii) Sewer and vault taxes and rents;

                  (iv) Annual license, permit and inspection fees except for
         those relating to construction of the Improvements, which shall be
         Seller's obligation in their entirety;

                  (v)  Intentionally omitted;

                  (vi) All charges and payments for water and sewer services
         supplied to the Property, provided, however, that if there is not meter
         or if the current bill for any of such utilities has not been issued
         prior to the Closing Date, the charges therefor shall be adjusted at
         the Closing on the basis of the charges for the prior period for which
         bills were issued and shall be further adjusted when the bills for the
         current period are issued; and

                  (vii) Amounts paid or outstanding for the water pipeline and
         traffic signalization under the Mutual Covenants in accordance with
         SECTION 5(a)(i)(3).

If any of the foregoing cannot be apportioned at the Closing because of the
unavailability of the amounts which are to be apportioned, such items shall be
apportioned as soon as practicable after the Closing Date.

         (b) The amount of any unpaid real property taxes and assessments, water
rates and charges and sewer taxes and rents which Seller is obligated to pay and
discharge may, at the option of Seller, be credited to Purchaser out of the cash
balance of the Purchase Price, provided that official bills therefor, indicating
the interest and penalties, if any, thereon, are furnished by Seller at the
Closing.

         (c) If any refunds of real property taxes or assessments, water rates
and charges or sewer taxes and rents shall be made after the Closing, the same
shall be held in trust by Seller or Purchaser, as the case may be, and shall
first be applied to the unreimbursed costs incurred in obtaining the same, then
paid to any tenant at the Property who is entitled to the same and the balance,
if any, shall be paid to Seller (for the period prior to the Closing Date) and
to Purchaser (for the period commencing with the Closing Date).

         (d) If at the Closing Date the Property or any part thereof shall be or
shall have been affected by any general assessment or assessments or real
property taxes which are or may become payable in installments of which any
installment is then a charge or lien and has become payable, Seller shall pay or
cause to be paid the

                                       22

<PAGE>



unpaid installments of such assessments due prior to the Closing Date and
Purchaser shall pay or cause to be paid all installments which are due on or
after the Closing Date. The current installments shall be apportioned at the
Closing. Any special assessment made against the Property prior to the Closing
shall be paid by Seller prior to the Closing whether or not the payments
therefor are due and payable prior to the Closing.

         (e) If, on the Closing Date, there are any Purchaser Initiated Change
Orders (as defined in EXHIBIT B) which have not been fully paid for by
Purchaser, then the additional costs due to such Purchaser Initiated Change
Orders shall be paid by Purchaser at the Closing.

         (f) In the event the apportionments hereinabove provided which are to
be made at the Closing result in a credit balance (i) to Purchaser, such sum
shall be paid at the Closing, by giving Purchaser a credit against the balance
of the Purchase Price in the amount of such credit balance or (ii) to Seller,
Purchaser shall pay the amount thereof to Seller at the Closing by wire transfer
of immediately available funds to the account or accounts designated by Seller
in writing for the balance of the Purchase Price.

         (g) Seller shall be responsible for the payment of amounts due pursuant
to clause (ii) of the last paragraph of Section 2.3 of the Reciprocal Easement
Agreement dated as of March 25, 1999 between Seller and Polaroid Corporation,
filed with the South Registry District of Middlesex County as Document No.
1101666, and all other amounts due under the Contracts prior to the Closing
Date. Purchaser shall be responsible for all other amounts which arise under the
Contracts which are not due until on or after the Closing Date.

         (h) No insurance policies of Seller are to be transferred to Purchaser,
and no apportionment of the premiums therefor shall be made. Purchaser
acknowledges that it shall be responsible for securing its own insurance for the
Property as of the Closing Date.

         (i) The obligations of the parties hereto under this SECTION 8 shall
survive the Closing.

         9. CLOSING MATTERS The following items shall be provided for at the
Closing:

         (a)      PAYMENT OF RECORDING, TITLE AND OTHER FEES.

                                       23

<PAGE>



                           (i) RECORDING FEES. Seller shall pay the fee for
                  documentary deed stamps due in connection with the
                  consummation of the transactions contemplated by this
                  Agreement. Purchaser shall pay at the Closing all state, city,
                  county, municipal and other governmental recording fees in
                  connection with the conveyance of the Property.

                           (ii) TITLE FEES. Purchaser shall pay all charges and
                  fees and premiums of the Title Company in connection with the
                  examination of title. Purchaser shall pay all premiums of the
                  Title Company in connection with the title insurance policy,
                  if any, to be obtained by Purchaser.

                           (iii) OTHER CHARGES. Other charges, if any, shall be
                  paid in the manner in which purchasers and sellers of real
                  property in Middlesex County, Massachusetts customarily divide
                  such charges.

         (b) UTILITY DEPOSITS. Seller shall be entitled to any deposits made by
Seller with utility companies servicing the Property, and, if the same are not
refundable to Seller without replacement by Purchaser, Purchaser shall either:
(i) deliver the requisite replacement deposit to the utility company on or prior
to the Closing Date or (ii) pay to Seller at the Closing the amount of such
deposit, against reasonable evidence of such deposit and a good and sufficient
transfer by Seller to Purchaser of all interest of Seller in the deposit.

         (c) SURVIVAL. The obligations of Seller and Purchaser under this
SECTION 9 shall survive the Closing.

         10. TITLE EXAMINATION. (a) Purchaser shall obtain from a title company
licensed to do business in the Commonwealth of Massachusetts ("TITLE COMPANY") a
commitment for a title insurance policy and, in connection therewith, shall
cause title to the Property to be searched and examined by the Title Company,
and shall request that the Title Company deliver directly to Seller's counsel
copies of the Title Company's report, the tax and departmental searches and the
survey reading and any updates or continuations thereof and any supplements
thereto. No later than February 7, 2000, Purchaser shall deliver to Seller a
written statement setting forth any liens or encumbrances affecting, or other
defects in or objections to, title to the Property disclosed by such materials
other than Permitted Title Exceptions ("ADDITIONAL EXCEPTIONS"). The failure by
Purchaser to deliver any statement required by the immediately preceding
sentence within the time period specified therefor, or to include any matter in
any such statement which was delivered by Purchaser within the time period
specified therefor, shall constitute a waiver by Purchaser of any and

                                       24

<PAGE>



all Additional Exceptions which may be, or should have been, disclosed by the
materials to be covered by such statement and such Additional Exceptions shall
be deemed Permitted Title Exceptions as if fully set forth in EXHIBIT C hereto.
Notwithstanding any of the foregoing to the contrary, (i) Seller shall be
required to discharge prior to the Closing (or deliver at the Closing
instruments sufficient, upon filing with the Land Court, to discharge such
matters from title to the Property)_ all title encumbrances evidencing monetary
indebtedness of Seller, including without limitation a mortgage, assignment of
leases and rents and uniform commercial code financing statements from Seller in
favor of Pacific Life Insurance Company ("FINANCIAL ENCUMBRANCES"), and (ii)
Seller shall exercise reasonable efforts to discharge prior to the Closing all
other title encumbrances which do not constitute Permitted Title Exceptions,
provided however that with respect to the discharge of matters referenced in
this clause (ii), Seller's "reasonable efforts" shall not be deemed to require
Seller to bring any legal action or proceeding or otherwise incur expenses in
excess of $250,000. All such matters described in clauses (i) and (ii) of the
preceding sentence which first became record title matters after January 2,
2000, also shall constitute "ADDITIONAL EXCEPTIONS."

         (b) Seller shall be entitled to reasonable adjournments of the Closing
during which Seller shall attempt to remove Additional Exceptions in accordance
with SECTION 10(a). If for any reason, despite Seller's efforts consistent with
the preceding sentence, Seller is unable, despite the exercise of reasonable
efforts, to remove any Additional Exception (other than Financial Encumbrances
or Additional Exceptions voluntarily entered into by Seller in violation of this
Agreement, which Seller shall remove), as of the Closing Date, as such date may
be adjourned pursuant to this SECTION 10(b), Seller shall so notify Purchaser.
If such notice is given by Seller, Purchaser shall elect (i) to terminate this
Agreement by giving notice to Seller, in which event the provisions of SECTION
13(b) shall apply or (ii) to perform all of Purchaser's obligations hereunder
and accept title to the Property subject to such uncured Additional Exceptions
without any abatement of the Purchase Price or liability on the part of Seller.
Purchaser shall make its election between clauses (i) and (ii) of the
immediately preceding sentence by written notice to Seller given not later than
5:00 P.M. on the fifth Business Day after the giving of the notice by Seller of
its inability or unwillingness to remove such Additional Exceptions. If
Purchaser shall fail or refuse to give such written notice as aforesaid, it
shall be deemed to have elected clause (ii) above and the Closing shall take
place on the Closing Date.

         (c) At Purchaser's reasonable request, Seller agrees to exercise
reasonable efforts (which shall not require the expenditure of any funds other
than minimal legal or consultants' fees) during the pendency of this Agreement
to obtain (i) from Polaroid Corporation and MMS Winter Street, L.L.C. an
acknowledgement or

                                       25

<PAGE>



release to the effect that there are no ongoing obligations on the part of
Seller (or, following the Closing, Purchaser) with respect to the Polaroid
Utility Easement, Polaroid Driveway Easement and Common Drainage Easement
encumbering Lots 8 and 10 as shown on the "Survey of Lot 9 in Waltham,
Massachusetts" prepared by Martinage Engineering Associates, Inc. for Bren
Schreiber Properties, Inc. dated March 11, 1999 and (ii) certificates from the
other parties to the contracts regarding any outstanding obligation of Seller.

         11. RISK OF LOSS. (a) If a part of the Property is destroyed or damaged
by fire or other casualty, Seller shall promptly notify Purchaser of such fact.
Seller shall have the right to terminate this Agreement by giving notice to
Purchaser not later than ten (10) days after the giving of Seller's notice if,
despite Seller's best efforts, Seller's existing mortgagee refuses to release
casualty proceeds in accordance with the terms of its mortgage encumbering the
Property and the part of the Property damaged or destroyed has a value, as
reasonably determined by Seller, in excess of One Million and 00/100 Dollars
($1,000,000.00). Seller also shall have the right to terminate this Agreement if
such casualty occurs after Seller delivers the Closing Notice but prior to the
Closing Date by giving notice to Purchaser not later than ten (10) days after
the giving of Seller's notice if the part of the Property damaged or destroyed
has a value, as reasonably determined by Seller, in excess of Seven Million Five
Hundred Thousand and 00/100 Dollars ($7,500,000.00). Purchaser shall have the
right to terminate this Agreement if such casualty occurs after Seller delivers
the Closing Notice but prior to the Closing Date by giving notice to Seller not
later than ten (10) days after the giving of Seller's notice if the part of the
Property damaged or destroyed has a value, as reasonably determined by Seller,
in excess of Five Hundred Thousand and 00/00 Dollars ($500,000.00). If either
party elects to terminate this Agreement as aforesaid, this Agreement shall
terminate and be of no further force and effect and neither party shall have any
liability to the other hereunder, except that Seller shall be obligated to
return to Purchaser the Downpayment. If neither Seller nor Purchaser elects to
terminate this Agreement as aforesaid, or if there is damage to or destruction
of an "immaterial part" (i.e., anything other than a material part) of the
Property by fire or other casualty, then the sale of the Property shall be
consummated as herein provided at the Purchase Price (without abatement) and
Seller shall assign to Purchaser (without recourse) at the Closing the rights of
Seller to the proceeds, if any, under Seller's insurance policies covering the
Property with respect to such damage or destruction, and Purchaser shall be
entitled to receive and keep any moneys received from such insurance policies.
Seller shall cause the Property to be insured until the Closing with insurance
at not less than the limits at which the Property currently is insured, as
evidenced by insurance certificates or binders previously delivered to
Purchaser.

                                       26

<PAGE>



         (b) If all or any significant portion of the Property is taken by
eminent domain (or is the subject of a pending taking which has not yet been
consummated), Seller shall notify Purchaser of such fact promptly after
obtaining knowledge thereof and either Purchaser or Seller shall have the right
to terminate this Agreement by giving notice to the other not later than ten
(10) days after the giving of Seller's notice. For the purposes hereof, a
"significant portion" of the Property shall mean such a portion of the Property
as shall negatively impact the value of the Property by an amount, as reasonably
determined by Seller, in excess of Five Hundred Thousand and 00/00 Dollars
($500,000.00), or otherwise negatively affects zoning, parking or access. If
either party elects to terminate this Agreement as aforesaid, this Agreement
shall terminate and be of no further force and effect and neither party shall
have any liability to the other hereunder, except that Seller shall be obligated
to return to Purchaser the Downpayment. If neither Seller nor Purchaser elects
to terminate this Agreement as aforesaid, or if an "insignificant portion"
(I.E., anything other than a significant portion) of the Property is taken by
eminent domain (or becomes the subject of a pending taking), then the sale of
the Property shall be consummated as herein provided at the Purchase Price
(without abatement) and Seller shall assign to Purchaser (without recourse) at
the Closing all of Seller's right, title and interest in and to all awards, if
any, for the taking, and Purchaser shall be entitled to receive and keep all
awards for the taking of the Property or such portions thereof.

         (c) The parties' obligations, if any, under this SECTION 11 shall
survive the Closing.

         12. BROKERAGE. Each of Purchaser and Seller represents and warrants to
the other that it has not hired, retained or dealt with any broker, consultant,
intermediary or finder in connection with the negotiation, execution or delivery
of this Agreement or the consummation of the transactions contemplated hereby to
whom a commission is or will be owed other than Grubb & Ellis and McCall & Almy,
Inc. Seller and Purchaser each covenant and agree to indemnify the other against
liability arising out of any breach or inaccuracy of the aforesaid
representation or warranty. Seller shall be solely responsible for the brokerage
commission due to Grubb & Ellis and for $800,000.00 of the brokerage commission
due to McCall & Almy, Inc. in connection with the transactions contemplated by
this Agreement, but only if, as and when the Deed is delivered to Purchaser and
recorded and the full Purchase Price is paid to Seller. Purchaser shall be
responsible for any other brokerage commission due to McCall & Almy, Inc. in
connection with the transactions contemplated by this Agreement. The provisions
of this SECTION 12 shall survive the Closing.

         13. REMEDIES. (a) The parties hereto agree that in the event Purchaser
defaults in its obligation to deliver the Purchase Price at the Closing or
otherwise

                                       27

<PAGE>



perform its obligations at the Closing, Seller may terminate this Agreement by
written notice to Purchaser and receive Two Million and 00/100 Dollars
($2,000,000.00) (plus any Interest on the Downpayment) as liquidated damages,
and Purchaser thereafter shall not have any further liability or obligation to
Seller at law or in equity. The Downpayment (plus any Interest on the
Downpayment) shall be released to Seller to satisfy (if Purchaser delivered the
Additional Downpayment) or partially to satisfy (if Purchaser did not deliver
the Additional Downpayment) the liquidated damages to be paid to Seller. If
Purchaser did not deliver the Additional Downpayment, then upon such termination
of this Agreement, Purchaser immediately shall deliver to Seller the amount of
Seven Hundred Fifty Thousand and 00/100 Dollars ($750,000.00), which, together
with the Initial Downpayment and any interest accrued on the Initial
Downpayment, shall be paid to Seller as liquidated damages. Purchaser's
obligation to deliver such liquidated damages to Seller, including without
limitation such $750,000.00, shall survive the termination of this Agreement.
Seller and Purchaser agree and acknowledge that Seller's actual damages in the
event of default by Purchaser would be extremely difficult or impossible to
ascertain and that the amount of liquidated damages provided herein is
reasonable in light of anticipated loss caused by such a default and the
difficulties of proof of loss.

         (b) In the event that on the Closing Date, Seller shall be unable,
despite the exercise of commercially diligent efforts, to perform its
obligations or to satisfy any condition applicable to Seller hereunder in
accordance with the provisions of this Agreement or to cause the title to the
Property to comply with this Agreement and this Agreement shall be terminated in
accordance with its terms as a result thereof, the sole liability of Seller
shall be to return the Downpayment, together with the Interest, to Purchaser,
and upon such return, this Agreement shall be deemed terminated and Seller shall
not have any further liability or obligations to Purchaser hereunder nor shall
Purchaser have any further liability or obligation to Seller hereunder, except
for such liabilities or obligations as are specifically stated to survive the
termination of this Agreement.

         (c) In the event that Seller willfully defaults in its obligation to
transfer the Property in accordance with this Agreement, Purchaser shall be
entitled to such remedies against Seller as are available at law or in equity,
including the rights to damages and specific performance of this Agreement.

         14. NOTICES. All notices and other communications required or permitted
hereby shall be in writing and shall be deemed to have been duly and
sufficiently given if personally delivered with proof of delivery thereof (any
notice or communication so delivered being deemed to have been received at the
time so delivered), or

                                       28

<PAGE>



sent by United States registered or certified mail, postage prepaid, at a post
office regularly maintained by the United States Postal Service (any notice or
communication so sent being deemed to have been received two (2) Business Days
after mailing in the United States), or by electronic facsimile transfer (any
notice or communication so sent being deemed to have been received at the time
indicated on the sender's receipt of transfer) addressed to the respective
parties as follows:

         (a)  if to Seller:

                  Best Property Fund, L.P.
                  c/o Bren Schreiber Properties, Inc.
                  125 Summer Street, Suite 1640
                  Boston, Massachusetts 02110
                  Attention:  David S. Hall
                  Fax:  (617) 345-9200

                  with a copy to:

                  Edward S. Hershfield, Esq.
                  Brown, Rudnick, Freed & Gesmer, P.C.
                  One Financial Center
                  Boston, Massachusetts 02111

                  Fax: (617) 856-8201

         (b)      if to Purchaser:

                  Praecis Pharmaceuticals Incorporated
                  One Hampshire Street
                  Cambridge, Massachusetts 02139
                  Attention: Kevin F. McLaughlin, Chief Financial Officer
                  Fax: (617) 494-8414

                  with a copy to:

                  Michael H. Glazer, Esquire
                  Goodwin, Proctor & Hoar LLP
                  Exchange Place
                  Boston, Massachusetts 02109-2881
                  Fax:  (617) 227-8591

                  and with a copy to:

                                       29

<PAGE>



                  Mary L. Lentz
                  McCall & Almay, Inc.
                  One Post Office Square
                  Boston, Massachusetts 02109
                  Fax:  (617) 542-4499

Either party may, by notice given as aforesaid, change the person or persons
and/or address or addresses, or designate an additional person or persons or an
additional address or addresses, for its notices, PROVIDED, HOWEVER, that notice
of change of address or addresses shall only be effective upon receipt. All
notices from Seller to Purchaser or from Purchaser to Seller pursuant to this
Agreement will be effective if executed by their respective attorneys (including
facsimile transfer).

         15. FOREIGN INVESTMENT IN REAL PROPERTY TAX ACT. At the Closing, Seller
shall deliver to Purchaser an affidavit in the form required by Section 1445 at
the Code, to the effect that Seller is not a "foreign person" as defined in
Section 1445 of the Code.

         16. CHOICE OF LAW. The interpretation, enforcement and performance of
this Agreement shall be governed by the laws of the Commonwealth of
Massachusetts applicable to agreements made and to be performed wholly within
such Commonwealth.

         17. MISCELLANEOUS. (a) ENTIRE AGREEMENT; EXHIBITS. The Confidentiality
Agreement and this Agreement, together with the exhibits hereto, constitutes the
entire agreement of the parties hereto regarding the subject matter of this
Agreement and all other prior or contemporaneous agreements, understandings,
representations and statements, oral or written, hereby are merged herein. All
exhibits attached hereto are hereby incorporated herein and made a part hereof
by reference as fully as though set forth herein. Without limiting the
generality of the foregoing, that certain Letter of Intent dated December 23,
1999 between Seller and Purchaser is of no further force and effect, it having
been superceded by the terms of this Agreement.

         (b) AMENDMENTS. This Agreement may not be modified, amended, altered,
supplemented or cancelled except pursuant to the terms hereof or an instrument
in writing signed by the parties hereto.

         (c) ACCEPTANCE OF THE DEED. The acceptance of the Deed to the Property
by Purchaser shall be deemed an acknowledgment by Purchaser that Seller has
fully complied with all of its obligations hereunder and that Seller is
discharged therefrom and that Seller shall have no further obligation or
liability with respect to any of the

                                       30

<PAGE>



agreements made by Seller in this Agreement, except for those provisions of this
Agreement which expressly provide that any obligations of Seller shall survive
the Closing.

         (d) INDEMNIFICATION GENERALLY. Wherever it is provided in this
Agreement or in any agreement or document delivered pursuant hereto that a party
shall indemnify another party hereunder against liability or damages, such
phrase and words of similar import shall mean that the indemnifying party hereby
agrees to and does indemnify, defend and hold harmless the indemnified party and
such party's direct and indirect shareholders, partners and/or members and their
respective past, present and future officers, directors, employees and agents
from and against any and all costs, claims, demands, suits, judgments,
interests, damages, losses, liabilities and expenses (including without
limitation reasonable attorneys' fees and disbursements) to which they or any of
them may become subject or which may be incurred by or asserted against any or
all of them attributable to, arising out of or in connection with the matters
provided for in such provision. The provisions of this SECTION 17(d) shall
survive the Closing or earlier termination of this Agreement.

         (e) BINDING EFFECT. This Agreement does not constitute an offer to sell
or purchase and shall not bind Seller or Purchaser unless and until Seller and
Purchaser elect to be bound hereby by executing and delivering to one another an
executed original counterpart hereof and Seller receives the Initial Downpayment
in accordance with the terms of this Agreement and such funds have cleared.

         (f) PARTIAL INVALIDITY. If any term or provision of this Agreement or
the application thereof to any persons or circumstances shall, to any extent, be
invalid or unenforceable, the remainder of this Agreement or the application of
such term or provision to persons or circumstances other than those as to which
it is held invalid or unenforceable shall not be affected thereby, and each term
and provision of this Agreement shall be valid and enforceable to the fullest
extent permitted by law.

         (g) RECORDATION OF AGREEMENT. Neither Seller nor Purchaser may record
this Agreement or any notice of this Agreement. To the extent that any such
filing is made by Purchaser in violation of this Agreement, Purchaser shall
indemnify Seller against any damages incurred by Seller in connection therewith.
The provisions of this SECTION 17(g) shall survive the termination of this
Agreement.

         (h) FURTHER ASSURANCES. The parties mutually agree to execute and
deliver to each other, at the Closing, such other and further documents as may
be reasonably required by counsel for the parties to carry into effect the
purposes and intents of this Agreement, provided such documents are customarily
delivered in real estate

                                       31

<PAGE>



transactions in Massachusetts and do not impose any material obligations upon
any party hereunder which are inconsistent with the terms of this Agreement.

         (i) NONIMPUTATION. Neither party to this Agreement nor any other
corporation or entity referred to herein shall have imputed to it the knowledge
of any agent, officer, servant or employee thereof unless and until such agent,
officer, servant or employee has actual knowledge of the relevant event, notice,
condition, occurrence, fact or situation or has reasonable cause to know, or
should reasonably be aware thereof and then only if such event, notice,
condition, occurrence, fact or situation is related to matters as to which such
agent, officer, servant or employee is entrusted and with which has authority to
deal.

         (j) PREVAILING PARTY COSTS. In the event any dispute between the
parties hereto results in litigation, the prevailing party shall be reimbursed
and indemnified by the party not prevailing in such dispute for all costs and
expenses reasonably incurred by the prevailing party in enforcing or
establishing its rights hereunder, including without limitation court costs and
reasonable attorneys' fees and disbursements. The prevailing party shall be
determined by the court based upon an assessment of which party's major
arguments or positions taken in the proceedings could fairly be said to have
prevailed over the other party's major arguments or positions on major disputed
issues. The provisions of this SECTION 17(j) shall survive the Closing or
earlier termination of this Agreement.

         (k) HEADINGS; SECTION AND EXHIBIT REFERENCES. The section headings used
herein are for reference purposes only and do not control or affect the meaning
or interpretation of any term or provision hereof and shall not be deemed in any
manner to modify, explain, qualify or restate any of the provisions of this
Agreement. All references in this Agreement to sections and exhibits are to the
sections hereof and the exhibits attached hereto, respectively.

         (l) COUNTERPARTS. This Agreement may be executed in any number of
counterparts with the same effect as if all parties hereto had executed the same
document. All such counterparts shall be construed together and shall constitute
one instrument.

         (m) ASSIGNMENT. Neither party hereto may assign its respective rights
and obligations hereunder, in whole or in part, without the prior written
consent of the other party hereto. Any assignment without such prior written
consent shall be deemed null and void. Subject to and without limiting the
preceding two sentences, this Agreement shall bind and inure to the benefit of
the respective heirs, executors, administrators, personal representatives,
successors and assigns of the parties hereto.

                                       32

<PAGE>



Notwithstanding the foregoing, immediately prior to the Closing, Purchaser may
assign its rights under this Agreement, following written notice to Seller, to
any affiliated entity or to an entity with which Purchaser shall perform a
sale/leaseback transaction, a synthetic lease transaction or another similar
transaction provided that any such assignment shall not result in a violation of
ERISA.

         (n) NO WAIVER. The failure of any party hereto to enforce at any time
any of the provisions of this Agreement shall in no way be construed as a waiver
of any of such provisions, or the right of any party thereafter to enforce each
and every such provision. No waiver of any breach of this Agreement shall be
held to be a waiver of any other or subsequent breach.

         (o) NO OTHER PARTIES. The representations, warranties and agreements of
the parties contained herein are intended solely for the benefit of the parties
to whom such representation, warranties or agreements are made, shall confer no
rights hereunder, whether legal or equitable, in any other party, and no other
party shall be entitled to rely thereon.

         (p) CONSTRUCTION. This Agreement shall not be construed more strictly
against one party than against the other, merely by virtue of the fact that it
may have been drafted or prepared by counsel for one of the parties, it being
recognized that both Seller and Purchaser have contributed substantially and
materially to the preparation of this Agreement.

         (q) DUE AUTHORIZATION. Each party represents and warrants that the
individual and/or entity executing this Agreement on behalf of such party has
the capacity set forth on the signature pages hereof with full power and
authority to bind the party on whose behalf such individual and/or entity is
executing this Agreement to the terms hereof.

         (r) TIME OF THE ESSENCE. Time is of the essence in the performance of
and compliance with each of the provisions and conditions of this Agreement.

         (s) NO PARTNERSHIP. Notwithstanding anything to the contrary contained
herein, this Agreement shall not be deemed or construed to make the parties
hereto partners or joint venturers, or to render either party liable for any
debts or obligations of the other, it being the intention of the parties merely
to create the relationship of seller and purchaser with respect to the Property
to be conveyed as contemplated hereby.

         (t) CONFIDENTIALITY. Without limiting the provisions of the
Confidential-

                                       33

<PAGE>

ity Agreement, each of Seller and Purchaser agrees that it shall keep the
contents of this Agreement and the transactions contemplated hereby confidential
until February 7, 2000. Notwithstanding the foregoing, Seller and Purchaser may
disclose the contents of this Agreement and the transactions contemplated hereby
to their respective agents, representatives, employees, consultants and legal
counsel, and Purchaser also may disclose the contents of this Agreement and the
transactions contemplated hereby to (i) potential lenders, (ii) potential
parties who may participate in the ownership of the Property with Purchaser,
and (iii) potential parties who may participate in a lease, sale/leaseback or
sublease transaction of the Property with Purchaser.

         (u) RELEASE. By proceeding with this transaction following the
expiration of the Due Diligence Period and Closing the transaction, Purchaser
shall be deemed to have made its own independent investigation of the Property,
the Information and the presence of Hazardous Materials (hereinafter defined) on
the Property as Purchaser deems appropriate. Accordingly, subject to Seller's
Warranties, the covenants to be performed by Seller prior to the Closing as
expressly set forth in this Agreement and the satisfaction of Purchaser's
conditions to the Closing set forth in SECTION 5(a), Purchaser, on behalf of
itself and all of its officers, directors, shareholders, employees,
representatives and affiliated entities (collectively, the "RELEASORS") as of
the Closing, shall be deemed to, and shall have expressly waived and
relinquished any and all rights and remedies Releasors may now or hereafter have
against Seller, its successors and assigns, partners, shareholders, officer
and/or directors (the "SELLER PARTIES"), whether known or unknown, which may
arise from or be related to (i) the physical condition, quality, quantity and
state of repair of the Property and the prior management and operation of the
Property, (ii) the Information, (iii) the Property's compliance or lack of
compliance with any federal, state or local laws or regulations, and (iv) any
past, present or future presence or existence of Hazardous Materials on, under
or about the Property or with respect to any past, present or future violation
of any rules, regulations or laws, now or hereafter enacted, regulating or
governing the use, handling, storage or disposal of Hazardous Materials,
including, without limitation, (i) any and all rights and remedies Releasors may
now or hereafter have under the Comprehensive Environmental Response
Compensation and Liability Act of 1980 ("CERCLA"), the Superfund Amendments and
Reauthorization Act of 1986, the Resource Conservation and Recovery Act, the
Toxic Substance Control Act, Massachusetts General Laws, Chapter 21C and
Massachusetts General Laws, Chapter 21E, all as amended, and any similar state,
local or federal environmental law, rule or regulation, and (ii) any and all
claims, whether known or unknown, now or hereafter existing, with respect to the
Property under Section 107 of CERCLA (42 U.S.C.A. Section 9607). As used herein,
the teRM "HAZARDOUS MATERIAl(s)" includes, without limitation, any hazardous or
toxic materials substances or wastes, such as (1)

                                       34

<PAGE>



any materials, substances or wastes which are toxic, ignitable, corrosive or
reactive and which are regulated by any state or local governmental authority,
or any agency of the United States government, (2) any other material,
substance, or waste which is defined or regulated as a hazardous material,
extremely hazardous material, hazardous waste or toxic substance pursuant to
any laws, rules, regulations or orders of the United States government, or any
state or local governmental body, (3) asbestos, (4) petroleum and petroleum
based products, (5) formaldehyde, (6) polychlorinated biphenyls (PCBs), and (7)
freon and other chlorofluorocarbons. The provisions of this SECTION 17(u) shall
survive the Closing.

                  (v) Section 1031 Exchange. Seller may consummate the sale of
the Property as part of a so-called like kind exchange (the "EXCHANGE") pursuant
to Section 1031 of the Code, provided that any such exchange transaction, and
the related documentation, shall: (i) be at the sole cost and expense of Seller,
(ii) not require Purchaser to execute any contract, make any commitment, or
incur any obligations, contingent or otherwise, to third parties, (iii) not
cause Purchaser to be liable or potentially liable for any environmental
conditions affecting property other than the Property, (iv) not delay the
closing of the transaction contemplated by this Agreement, (v) not include
Purchaser's acquiring title to any property other than the Property or otherwise
becoming involved in a transaction with third party, and (vi) not otherwise be
contrary to or inconsistent with the terms of this Agreement. Notwithstanding
anything to the contrary contained herein, Purchaser is not to incur any, and
Seller shall reimburse, indemnify and hold Purchaser harmless from, any and all
costs, expenses and liabilities incurred solely from Purchaser's accommodation
of such tax deferred exchange, including, without limitation, reasonable
attorneys' fees, and any title or escrow fees or expenses. The obligations of
Seller and Purchaser under this SECTION 17(v) shall survive the Closing and
shall not be merged therein.

                  (w) WAIVER OF JURY TRIAL. To the extent permitted by
applicable law, the parties hereby waive any right to trial by jury in any legal
proceeding arising out of or relating to this Agreement or the transactions
contemplated hereby.

                  (x) NO PERSONAL LIABILITY. Notwithstanding anything stated to
the contrary herein, Seller's liability under this Agreement shall be limited to
Seller's interest in the Property and the proceeds therefrom and neither Seller,
Seller's asset manager, nor Seller's partners, nor any member, director,
employee, or agent of any of the foregoing shall have any personal liability
hereunder. The provisions of this SECTION 17(x) shall survive the Closing or
earlier termination of this Agreement.

                                       35

<PAGE>



                  (y) REPORTING. Seller shall satisfy any reporting requirements
arising under Section 6405 of the Code. The provisions of this Section 17(y)
shall survive the Closing.

                          [SEE SIGNATURES ON NEXT PAGE]

                                       36

<PAGE>



                  IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be executed under seal as of the day and year first above written.

                                   SELLER:

                                   BEST PROPERTY FUND, L.P., a Delaware
                                   limited partnership

                                   By: BBS INVESTORS II, a Delaware general
                                       partnership, its general partner

                                   By: SCHREIBER DEVELOPMENTS, LLC,
                                       a California limited liability company, a
                                       general partner

                                       By: /s/ Charles J. Schreiber, Jr.
                                           ------------------------------
                                           Charles J. Schreiber, Jr.,
                                           Manager

                                       PURCHASER:

                                       PRAECIS PHARMACEUTICALS IN
                                       CORPORATED

                                       By: /s/ Malcolm L. Gefter
                                           ------------------------------
                                           Name:
                                           Title:

                                       37

<PAGE>



         Escrow Agent hereby acknowledges receipt of the Initial Downpayment,
subject to collection, and agrees to serve as escrow agent in accordance with
the provisions of this Agreement.

                                            OWN RUDNICK FREED & GESMER, P.C.

                                            By:  /s/ Edward S. Hershfield
                                                 ----------------------------
                                                 Edward S. Hershfield, Member

                                       38

<PAGE>



                      EXHIBIT A - LEGAL DESCRIPTION OF LAND



                                       39


<PAGE>

                                    EXHIBIT A


A certain parcel of land off Winter Street, in Waltham, Middlesex County,
Massachusetts, shown as Lot 9 on Land Court Plan No. 30618E, a copy of a portion
of which is filed with the Middlesex South Registry District of the Land Court
with Certificate of Title No. 214324 in Registration Book 1201, Page 174.

Together with the benefit of rights reserved in Easement dated July 14, 1997,
filed as Document No. 1036276, and recorded in Book 27478, Page 136; as affected
by Utility Easement from owners of Lots 2 and 3 on Land Court Plan #30618C and
Lots 2, 3, B and C on Plan #669 of 1997, to Boston Edison Company and New
England Telephone and Telegraph Company, d/b/a Bell Atlantic, dated August 27,
1998, filed as Document No. 1078157; as further affected by Reciprocal Access
and Utility Easement dated March 25, 1999, filed as Document No. 1101665 and
recorded March 26, 1999, as Instrument No. 503.

Together with the benefit of grant and reservation recited in Reciprocal Access
and Utility Easement with the owner of Lots 5 and 6 on Land Court Plan No.
30618D dated March 31, 1998, filed as Document No. 1061070, and recorded in Book
28405, Page 421, affecting areas shown as "Reserved Easement Area" on a plan
entitled "Easement Plan of Land in Waltham, Massachusetts," dated March 30,
1998, recorded therewith; as affected by First Amendment to Reciprocal Access
and Utility Easement and to Reciprocal Easement Agreement dated September 10,
1998, filed as Document No. 1079645, and recorded in Book 29108, Page 346; as
further affected by Reciprocal Access and Utility Easement dated March 25, 1999,
filed as Document No. 1101665 and recorded March 26, 1999, as Instrument No.
503, and by Reciprocal Easement Agreement dated March 25, 1999, filed as
Document No. 1101666.

Together with the benefit of Reciprocal Easement Agreement with the owner of
Lots 5 and 6 on Land Court Plan No. 30618D dated March 31, 1998, filed as
Document No. 1061071, and recorded in Book 28405, Page 443, affecting areas
shown on a plan entitled "Easement Plan of Land in Waltham, Massachusetts,"
dated March 30, 1998, recorded therewith; as affected by First Amendment to
Reciprocal Access and Utility Easement and to Reciprocal Easement Agreement
dated September 10, 1998, filed as Document No. 1079645, and recorded in Book
29108, Page 346; as further affected by Reciprocal Easement Agreement dated
March 25, 1999, filed as Document No. 1101666.

Together with the benefit of Reciprocal Easement Agreement with the owner of Lot
8 on Land Court Plan No. 30618E dated March 10, 1999, filed as Document
No. 1099963.

Together with the benefit of Reciprocal Access and Utility Easement Agreement
with the owner of Lot 8 on Land Court Plan No. 30618E dated March 10, 1999,
filed as Document No. 1099964, and recorded March 10, 1999, as Instrument No.
1121; as further affected by Reciprocal Access


                                       40

<PAGE>


                                EXHIBIT A (CONT.)

and Utility Easement dated March 25, 1999, filed as Document No. 1101665 and
recorded March 26, 1999, as Instrument No. 503.

Together with the benefit of Reciprocal Access and Utility Easement dated March
25, 1999, filed as Document No. 1101665 and recorded March 26, 1999, as
Instrument No. 503.

Together with the benefit of Reciprocal Easement Agreement dated March 25, 1999,
filed as Document No. 1101666.

Together with the benefit of Mutual Covenants agreement dated March 25, 1999,
filed as Document No. 1101667.

Together with the benefit of Landscape License Agreement dated March 25, 1999,
filed as Document No. 1101668.


                                       41


<PAGE>


                            EXHIBIT B - SELLER'S WORK

I.       DEFINITIONS

         The following terms shall have the meanings specified in this Section
when used in this EXHIBIT B (the meanings specified are applicable to both the
singular and plural):

         APPLICABLE LAWS" shall mean all applicable federal, state and local
laws, codes, ordinances, rules, regulations, standards or orders of any public
authority having jurisdiction over the Property, including building, health,
labor, safety, licensing, environmental or zoning laws, codes, ordinances,
rules, regulations, standards or orders of any such public authority.

         ARCHITECT" shall mean Jung/Brannen Associates, Inc., who shall be
responsible for the design of the Seller's Work on behalf of Seller, pursuant
to the Design Contract (as hereinafter defined).

         "CONSTRUCTION CONTRACT" shall mean the construction contract dated as
of April 13, 1999 by and between Seller or its affiliates or agents and the
Contractor for the construction of the Seller's Work, as such construction
contract may be amended from time to time; provided, however, that no such
amendment shall affect Contractor's warranties set forth therein.

         "CONTRACTOR" shall mean John Moriarty & Associates, Inc., the general
contractor who will be responsible for constructing the Seller's Work on behalf
of Seller pursuant to the Construction Contract.

         "DESIGN CONTRACT" shall mean the design contract entered into by and
between Seller or its affiliates or agents and the Architect for the design of
the Seller's Work, as such design contract may be amended; provided, however,
that no such amendment shall affect Architect's warranties set forth therein.

         "EVENT OF FORCE MAJEURE" shall mean labor disputes, fire, unusual
delays in deliveries, unavoidable conditions or other causes beyond the
Contractor's control, or other causes which the Architect determines may justify
delay. "PLANS AND SPECIFICATIONS" shall mean the drawings, plans and written
requirements prepared by the Architect or engineers or other consultants which
describe improvements to be constructed at the Property and which have been
delivered to Purchaser prior to the date of this Agreement, and which are listed
on SCHEDULE 1 hereto.

                                       42

<PAGE>



         "RECORD DRAWINGS" shall mean, collectively, the Plans and
Specifications, together with all Addenda (hereinafter defined) approved by
Seller, all Seller Initiated Change Orders (hereinafter defined) approved by
Seller and all Purchaser Initiated Change Orders (hereinafter defined) approved
by Seller.

         "SELLER'S WORK" shall mean all labor, materials, equipment and
services, or any portion thereof, that are indicated on or are reasonably
inferable from the Record Drawings, or that are required in accordance with any
Applicable Law now in effect including, but not limited to, all types and
quantities of components, items, systems, materials and methods of construction.

         "SUBCONTRACTOR" shall mean any subcontractor or supplier in privity
with the Contractor at any tier.

II.      SELLER'S DUTIES AND RESPONSIBILITIES

         Seller shall be responsible for the following duties and
responsibilities:

         1.       Seller shall oversee the Contractor who shall cause the
                  Seller's Work to be constructed in accordance with the Record
                  Drawings.

         2.       Seller shall provide construction and design administration
                  services and coordinate all portions of the Seller's Work
                  (provided that Seller shall not have responsibility for or
                  have control over the construction means, methods, techniques,
                  sequences and procedures affecting the Seller's Work).

         3.       Seller shall take all other actions reasonably necessary to
                  perform its obligations as set forth in this EXHIBIT B.

         4.       Seller shall oversee the efforts of the Contractor who shall
                  establish and implement adequate procedures for processing and
                  approval of shop drawings, product data, samples and other
                  submittals.

         5.       Seller shall oversee the efforts of the Contractor who shall
                  maintain appropriate record copies of all subcontracts,
                  drawings, specifications, Addenda, Seller Initiated Change
                  Orders, Purchaser Initiated Change Orders and other
                  modifications in good order. Seller shall monitor the efforts
                  of the Contractor who shall mark-up the Plans and
                  Specifications to reflect changes as they occur which shall be
                  turned over to Seller upon completion of the Seller's Work.

                                       43

<PAGE>



         6.       Seller shall monitor the Contractor's management of the
                  performance of Subcontractors.

         7.       Seller shall coordinate inspections by the Architect with the
                  Contractor.

         8.       Seller shall coordinate the efforts of Purchaser, the
                  Architect and the Contractor in Punch List compilation. Seller
                  shall monitor the efforts of the Contractor in the completion
                  of the Punch List items.

         9.       Seller shall secure from the Contractor all warranties and
                  guaranties for the benefit of Purchaser, manuals, Record
                  Drawings and keys upon final completion.

III.     INSPECTION AND ENTRY

         From and after the date of this Agreement, Purchaser and its agents
         shall have the right to enter onto the Property from time to time
         during construction to observe and inspect the Seller's Work; provided
         such entry shall be at the sole risk of Purchaser and that Seller shall
         not be liable in any way for any injury, loss or damage which may occur
         to any of the installations made or to property placed therein or for
         any delay in the delivery of the Property or the completion of the
         Seller's Work caused by such entry and installations. Purchaser shall
         cooperate with Seller in all respects and shall not interfere with
         construction activities of the Contractor in connection with the
         completion of the Seller's Work, and Purchaser shall immediately comply
         with any directive of Seller with respect to activities at the
         Property.

IV.      CHANGES IN THE WORK

         1.       ADDENDA AND SELLER INITIATED CHANGE ORDERS

         Seller may approve addenda and minor changes and substitutions, such as
         field changes to the Plans and Specifications (collectively, "ADDENDA")
         and may approve change orders to the Plans and Specifications proposed
         by Seller, Architect and/or Contractor ("SELLER INITIATED CHANGE
         ORDERS"); provided, however, that the same (A) do not modify the Plans
         and Specifications in any material respect, unless Purchaser has
         granted (or has been deemed to have granted) its prior written
         approval, which may be granted or withheld in Purchaser's sole
         discretion; (B) do not reduce the scope, quality, quantity, function or
         intent of Seller's Work as specified in the Plans and

                                       44

<PAGE>



         Specifications, unless Purchaser has granted its prior written
         approval, which may be granted or withheld in Purchaser's sole
         discretion; and (C) do not otherwise change the quality of the Seller's
         Work, unless Purchaser has granted (or has been deemed to have granted)
         its prior written approval, which approval shall not be unreasonably
         withheld or delayed. If Seller requests Purchaser's written approval
         pursuant to this SECTION (IV)(1), Purchaser shall respond to any such
         request within seven (7) days. If such response is a refusal to grant
         approval, it shall contain Purchaser's reasons for refusing to grant
         the requested approval. If Purchaser fails to respond to any such
         request for written approval within such seven (7) days period, as a
         result of such failure, Purchaser shall be deemed to have granted its
         prior written approval as requested by Seller.

         2.       PURCHASER INITIATED CHANGE ORDERS

         A.       Purchaser acknowledges that the Plans and Specifications do
                  not include tenant improvements, amenity spaces, signs,
                  directories, decorations, fixtures or other upgrades. Except
                  as otherwise provided herein, no extra work (including,
                  without limitation, increases in the scope of the Seller's
                  Work) or changes in the Seller's Work requested by Purchaser (
                  "PURCHASER'S INITIATED CHANGE") shall be made except in
                  accordance with a duly issued written change order authorizing
                  such Purchaser Initiated Change ("PURCHASER INITIATED CHANGE
                  ORDER"), notwithstanding the course of dealing between, or the
                  course of performance of, the parties or industry standards.
                  No work under a Purchaser Initiated Change Order shall be
                  carried out unless Seller has received funds from Purchaser to
                  fund any such Purchaser Initiated Change Order. Any such funds
                  shall be conclusively deemed to be fully earned when the work
                  to be performed pursuant to such Purchaser Initiated Change
                  Order is completed, and shall not be subject to refund or
                  offset under any other circumstances, unless Seller defaults
                  in its obligations under this Agreement. All Purchaser
                  Initiated Change Orders shall be executed in writing by
                  Purchaser and Seller and Seller may elect to execute or not
                  execute any such Purchaser Initiated Change Order, in Seller's
                  sole discretion, except that Seller shall not unreasonably
                  refuse to execute any such Purchaser Initiated Change Order
                  which (i) improves the Improvements; (ii) does not delay the
                  performance of the Seller's Work or require new licenses,
                  permits or approvals or resubmission or modification of
                  existing licenses, permits or approvals; and (iii) does not
                  require the

                                       45

<PAGE>



                  removal of any of the components of the Seller's Work in the
                  event the Improvements are used as an office building.

         B.       In connection with any Purchaser Initiated Change, Seller
                  shall submit, in writing, to Purchaser, a proposed Purchaser
                  Initiated Change Order for accomplishing such Purchaser
                  Initiated Change, which proposed Purchaser Initiated Change
                  Order shall reflect the change in the amount due to the
                  Contractor pursuant to the Construction Contract and in
                  addition shall indicate the additional construction time, if
                  any, due to such proposed Purchaser Initiated Change.
                  Purchaser shall respond to such proposed Purchaser Initiated
                  Change Order within five (5) days following receipt.

         V.       CHANGES IN SCHEDULE

                  1.       SCHEDULE

                  Seller has provided Purchaser with a construction schedule,
                  prepared by the Contractor, detailing the scheduling and
                  timing of the Seller's Work, and indicating a Final Completion
                  date prior to September 1, 2000 ( "SCHEDULE"), it being
                  understood that the Schedule shall be updated by Seller from
                  time to time to reflect the actual progress of construction.

         2.       SUBSTANTIAL COMPLETION

                  Seller shall provide Purchaser not less than sixty (60) days
                  prior written notice of the anticipated date of Final
                  Completion (hereinafter defined). When Seller has achieved
                  Substantial Completion (as defined in the Construction
                  Contract) of the Seller's Work, Seller shall cause the
                  Architect to issue a certificate of Substantial Completion
                  with a copy to Purchaser. No later than two (2) Business Days
                  following Purchaser's receipt of such certificate of
                  Substantial Completion, Purchaser and Seller shall jointly
                  inspect the Seller's Work with the Architect. No later than
                  three (3) Business Days after such inspection, the Architect
                  shall prepare a list of all purported nondeminimus
                  discrepancies between the Record Drawings and the Seller's
                  Work as constructed ( "PUNCH LIST"), and shall deliver such
                  list to Seller and Purchaser. If Seller or Purchaser contest
                  the inclusion of any item in, or the omission of any item
                  from, the Punch List, then during the next four (4) Business
                  Day period, Seller, Purchaser

                                       46

<PAGE>



                  and the Architect shall cooperate in good faith to finalize
                  the Punch List. In the event that despite such cooperation,
                  Seller, Purchaser and the Architect are unable to finalize the
                  Punch List, then any disputes regarding the inclusion of any
                  item in, or the omission of any item from, the Punch List
                  shall be determined as follows: (A) Disputes involving items
                  having a cumulative value, as estimated by the Architect, not
                  in excess of $25,000, shall be determined by the Architect
                  within five (5) Business Days following such four (4) Business
                  Day period. (B) Disputes involving items having a cumulative
                  value as estimated by the Architect, in excess of $25,000,
                  shall be determined within five (5) Business Days following
                  such four (4) Business Day period by Peter Barber, presently
                  of Northland Development Corporation ("INITIAL ARBITRATOR")
                  or Robert M. Keeley, presently of Diversified Project
                  Management ("SECONDARY ARBITRATOR"), if the Initial Arbitrator
                  is not available. The Architect shall submit matters to the
                  Initial Arbitrator or the Secondary Arbitrator. All decisions
                  of the Architect, Initial Arbitrator and Secondary Arbitrator
                  pursuant to this SECTION V(2) shall be binding and conclusive.
                  After the Punch List is finalized pursuant to this SECTION
                  V(2), Seller shall proceed to cause the Punch List to be
                  completed as soon as reasonably practicable after Substantial
                  Completion All costs and expenses incurred with respect to the
                  Initial Arbitrator or the Secondary Arbitrator shall be shared
                  equally between Seller and Buyer.

         3.       FINAL COMPLETION

                  Final completion of the Seller's Work shall mean the date on
                  which the last of the following shall have occurred:

                  (a)      The completion of the Punch List, as certified by the
                           Architect.

                  (b)      The submission to Purchaser by the Seller of the
                           Record Drawings for the Seller's Work, along with all
                           warranties and guaranties, manuals and keys.

                  (c)      The submission to Purchaser by the Seller of final
                           lien releases and waivers from the Contractor and, if
                           available, all major Subcontractors, which releases
                           and waivers may be conditioned on receipt of amounts
                           due from Seller upon final completion of the
                           Seller's Work.

                                       47

<PAGE>



                  (d)      The removal from the Property by Seller of temporary
                           facilities, tools and similar items.

                  (e)      The issuance by the City of Waltham of a core and
                           shell certificate of occupancy for the Seller's
                           Work.

         Upon Final Completion, Seller shall notify Purchaser of the Closing
         Date in accordance with Section 4 of the Agreement.

         VI.      FINAL COMPLETION DATE

                  A.       The Seller agrees to use commercially diligent
                           efforts to cause Final Completion of the Seller's
                           Work to be achieved on or before September 1, 2000,
                           subject to Events of Force Majeure and Purchaser
                           Initiated Change Orders.

                  B.       If Final Completion is not achieved on or before
                           September 1, 2000 (which date shall be extended for
                           up to sixty (60) days for each day that the
                           construction of the Seller's Work was delayed because
                           of an Event of Force Majeure which date also shall be
                           extended by one day for each day that the
                           construction of the Seller's Work was delayed due to
                           Purchaser Initiated Change Orders), then, as
                           Purchaser's sole remedy on account of such delay
                           (other than Purchaser's termination right set forth
                           in SECTION 4 of this Agreement) for each day
                           thereafter until Final Completion is achieved, the
                           Purchase Price shall be reduced by $5,000 per day,
                           provided, however, that if Purchaser shall elect not
                           to exercise its right to terminate this Agreement as
                           of December 31, 2000 (or such later date as Purchaser
                           shall have the right to terminate this Agreement on
                           account of Purchaser Initiated Change Orders), all as
                           described in Section 4 of this Agreement, then the
                           $5,000 per day reduction in the Purchase Price shall
                           be tolled for thirty (30) days following Purchaser's
                           election (or deemed election) not so to terminate
                           this Agreement. Purchaser shall not lose the benefit
                           of any Purchase Price reduction that already shall
                           have accrued, and the $5,000 per day reduction shall
                           recommence to accrue following such thirty (30) day
                           period if Seller shall not then have achieved Final
                           Completion of the Seller's Work.


                                       48

<PAGE>



                                  SCHEDULE 1 -

                            PLANS AND SPECIFICATIONS


                                       49


<PAGE>

                  PROJECT BULLETINS/CHANGES AND CLARIFICATIONS
                       TO PROJECT PLANS AND SPECIFICATIONS

<TABLE>
<CAPTION>

                BULLETIN
                 NUMBER    DATE              TO                           FROM                     REFERENCES AND ATTACHMENTS
                --------------------------------------------------------------------------------------------------------------------
<S>             <C>       <C>       <C>                           <C>                        <C>

SPECIFICATIONS

                          08/05/99                                John G.  Crowe Associates  Specifications - Base Building - Shell
                                                                                                & Core Only Vol.  1
                          08/05/99                                John G.  Crowe Associates  Specifications - Base Building - Shell
                                                                                                & Core Only Vol.  2
                          08/20/99                                John G.  Crowe Associates  Site Preparation Binder
                          08/23/99                                John G.  Crowe Associates  CD Set L1 - L10 (L6 revised 10/26/99)
ARCHITECTURAL

                    1     08/31/99  John Moriarty & Associates    Jung Brannen Associates    SKA - 2R (revised)
                    2     08/31/99  John Moriarty & Associates    Jung Brannen Associates    SKA - 3A, 3B, 3C, 3D
                    3     08/31/99  John Moriarty & Associates    Jung Brannen Associates    SKA - 4A, 4B, 4C
                    4     09/03/99  John Moriarty & Associates    Jung Brannen Associates    SKA - 5A, 5B, 5C
                    5     09/03/99  John Moriarty & Associates    Jung Brannen Associates    Faxed sketch from JMA
                    8     10/07/99  John Moriarty & Associates    Jung Brannen Associates    SKA - 8
                    9     10/22/99  John Moriarty & Associates    Jung Brannen Associates    None
                   10     10/25/99  John Moriarty & Associates    Jung Brannen Associates    SKS - 101499 - 1, 2, 3
                   11     10/27/99  John Moriarty & Associates    Jung Brannen Associates    SKA - 9; AHA Sketch dated 10/26/99
                   12     10/27/99  John Moriarty & Associates    Jung Brannen Associates    Superceded by bulletin #17
                   13     11/02/99  John Moriarty & Associates    Jung Brannen Associates    SKA - 11
                   14     11/22/99  John Moriarty & Associates    Jung Brannen Associates    None
                   15     12/01/99  John Moriarty & Associates    Jung Brannen Associates    P - 3 and P - 4 revision 2; 11/23/99
                   16     12/01/99  John Moriarty & Associates    Jung Brannen Associates    None
                   17     12/08/99  John Moriarty & Associates    Jung Brannen Associates    SKA - 10; SKE - 6 - 9 incl.;
                                                                                               SKH - 2 - 4 incl.; SKFP - 1 & 2
                 None     09/29/99                                Jung Brannen Associates    SKA - 7
ENGINEERS

                          10/18/99  Jung Brannen Associates       McNamara/Salvia            Sketches for canopy

                          11/05/99  Jung Brannen Associates/      McNamara/Salvia            Marked up plan showing corrected
                                      John Moriarty & Associates                               dimensions for the second floor
                                                                                               opening.
OTHER

                    A     09/09/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 1 - 5
                    B     09/13/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 6 - 9
                    C     09/13/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 10 - 11
                    D     09/30/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 12, 13
                    E     10/05/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 14 - 19
                    F     10/05/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 20 - 21
                    G     10/05/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 22
                    H     11/10/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 23 - 27
                    I     12/02/99  John Moriarty & Associates    John G. Crowe Associates   SKL - 28
                    J     01/05/00  John Moriarty & Associates    John G. Crowe Associates   SKL - 29 - 31

</TABLE>


                                      50

<PAGE>

<TABLE>
<CAPTION>

DWG            TITLE                                      DATED       REC'D       ISSUED BY             COMMENTS

<S>            <C>                                        <C>         <C>         <C>                   <C>
CIVIL
C-1            Title Sheet                                2-Apr-98    23-Aug-99   John G. Crowe
L-1            Existing Conditions Plan                   2-Apr-98    23-Aug-99   John G. Crowe
L-2            Existing Conditions Plan                   2-Apr-98    23-Aug-99   John G. Crowe
L-3            Proposed Grading & Material Plan           2-Apr-98    23-Aug-99   John G. Crowe
L-4            Proposed Drainage & Utility Plan           2-Apr-98    23-Aug-99   John G. Crowe
L-5            Proposed Layout Plan                       2-Apr-98    23-Aug-99   John G. Crowe
L-6            Site Planting Plan                         2-Apr-98    23-Aug-99   John G. Crowe
L-7            Site Details                               2-Apr-98    23-Aug-99   John G. Crowe
L-8            Site Details                               2-Apr-98    23-Aug-99   John G. Crowe
L-9            Site Details                               2-Apr-98    23-Aug-99   John G. Crowe
L-10           Site Details                               2-Apr-98    23-Aug-99   John G. Crowe
GENERAL NOTES:

               First set
               Second Set:  19-Jul-99
               Third Set:  23-Aug-99

ARCHITECTURAL

A-001          Drawing list, Abbreviations, Desig's,      27-May-99   5-Aug-99    Jung/Brannen
                 Notes, Symbols & Code Sum
A-100          Basement Plan                              27-May-99   5-Aug-99    Jung/Brannen
A-101          First Floor Plan                           27-May-99   5-Aug-99    Jung/Brannen
A-102          Second Floor Plan                          27-May-99   5-Aug-99    Jung/Brannen
A-103          Third Floor Key Plan                       27-May-99   5-Aug-99    Jung/Brannen
A-104          Roof Plan                                  27-May-99   5-Aug-99    Jung/Brannen
A-201          Building Elevations                        27-May-99   5-Aug-99    Jung/Brannen
A-202          Typ. Enlarged Building Elevation           27-May-99   5-Aug-99    Jung/Brannen
A-203          Enlarged Atypical building & Entrance      4-Jun-99    5-Aug-99    Jung/Brannen
                 Elevation
A-211          Building Sections                          27-May-99   4-Aug-99    Jung/Brannen          Not updated
A-301          Wall Sections                              27-May-99   5-Aug-99    Jung/Brannen
A-302          Wall Sections                              4-Jun-99    5-Aug-99    Jung/Brannen
A-401          Egress Stairs & Corridors:  Plans &        4-Jun-99    5-Aug-99    Jung/Brannen
                 Sections
A-402          Egress Stair Plans:  Sections & Details    4-Jun-99    5-Aug-99    Jung/Brannen
A-411          Elevator Core. Cabs & Machine Rm:          4-Jun-99    5-Aug-99    Jung/Brannen
                 Plans, Sections & Details

A-421          First Floor Bathrooms & Locker Rooms:      27-May-99   5-Aug-99    Jung/Brannen
                 Plans, RCP's & Elevations
A-422          Second & Third Floor Bathrooms:  RCP's     4-Jun-99    5-Aug-99    Jung/Brannen
                 & Elevations
A-431          Atrium/Lobby:  First Floor Plan            4-Jun-99    5-Aug-99    Jung/Brannen
A-432          Atrium/Lobby:  Second & Third Floor Plan   4-Jun-99    5-Aug-99    Jung/Brannen
A-433          Atrium/Lobby:  First Floor Reflected       4-Jun-99    5-Aug-99    Jung/Brannen
                 Ceiling Plan
A-434          Atrium/Lobby:  Second & Third Floor RCP    4-Jun-99    5-Aug-99    Jung/Brannen
A-435          Atrium/Lobby:  Skylight Plan & Section     4-Jun-99    5-Aug-99    Jung/Brannen
A-436          Atrium/Lobby:  Section/Elevation           4-Jun-99    5-Aug-99    Jung/Brannen
A-437          Atrium/Lobby:  Section/Elevation           16-Jul-99   5-Aug-99    Jung/Brannen
A-438          Atrium/Lobby:  Elevations                  16-Jul-99   5-Aug-99    Jung/Brannen
A-439          Atrium/Lobby:  Elevations                  16-Jul-99   16-Jul-99   Jung/Brannen          Not updated
A-441          Rear Entrance & Corridor                   4-Jun-99    5-Aug-99    Jung/Brannen
A-451          Building Conference & Cafe                 16-Jul-99   5-Aug-99    Jung/Brannen
A-501          Exterior Details                           27-May-99   5-Aug-99    Jung/Brannen
A-502          Exterior Details                           4-Jun-99    5-Aug-99    Jung/Brannen
A-503          Exterior Details                           5-Aug-99    5-Aug-99    Jung/Brannen
A-504          Exterior Details                           5-Aug-99    5-Aug-99    Jung/Brannen
A-601          Door & Hardware Schedule:  Door Frame      4-Jun-99    5-Aug-99    Jung/Brannen
                 types: Details

A-801          Finish Schedule                            4-Jun-99    5-Aug-99    Jung/Brannen
A-901          Interior/Exterior - Details                4-Jun-99    5-Aug-99    Jung/Brannen
A-902          Atrium/Lobby - Details                     16-Jul-99   5-Aug-99    Jung/Brannen
A-903          Interior/Exterior - Details                16-Jul-99   5-Aug-99    Jung/Brannen
A-904          Interior/Exterior - Details                16-Jul-99   5-Aug-99    Jung/Brannen
</TABLE>

                                       51

<PAGE>

<TABLE>
<CAPTION>

DWG            TITLE                                      DATED       REC'D       ISSUED BY             COMMENTS

<S>            <C>                                        <C>         <C>         <C>                   <C>
A-905          Atrium/Lobby - Details                     5-Aug-99    5-Aug-99    Jung/Brannen

STRUCTURAL

S-100          General Notes I                            27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-101          General Notes II                           27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-200          Basement Foundation Plan                   27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-201          First Floor Plan                           27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-202          Second Floor Plan                          27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-203          Third Floor Plan                           27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-204          Roof Plan                                  27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-300          Column Schedule                            27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-301          Brace Frame Elevations                     27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-400          Concrete Details I                         27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-401          Concrete Details II                        27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-402          Concrete Details III                       27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-403          Concrete Details IV                        27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-500          Steel Details I                            27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-501          Steel Details II                           27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-502          Steel Details III                          27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-503          Steel Details IV                           27-May-99   5-Aug-99    Jung/Brannen/MC/Sal
S-504          Steel Details V                            4-Jun-99    5-Aug-99    Jung/Brannen/MC/Sal


FIRE PROTECTION

FP-1           Fire Alarm System Legend Riser & Notes     4-Jun-99    5-Aug-99    AHA Consulting Eng.
FP-2           Fire Alarm Basement Plan                   4-Jun-99    5-Aug-99    AHA Consulting Eng.   5-Aug-99
FP-3           Fire Alarm First Floor Plan                4-Jun-99    5-Aug-99    AHA Consulting Eng.   5-Aug-99
FP-4           Fire Alarm Second Floor Plan               4-Jun-99    5-Aug-99    AHA Consulting Eng.
FP-5           Fire Alarm Third Floor Plan                4-Jun-99    5-Aug-99    AHA Consulting Eng.
FP-6           Enlarged Reflected Ceiling Plan            16-Jul-99   5-Aug-99    AHA Consulting Eng.


PLUMBING

P-1            Legends, Schedules & Diagrams              4-Jun-99    2-Sep-99    AHA Consulting Eng.   5-Aug-99
P-2            Buried Piping Plan                         4-Jun-99    2-Sep-99    AHA Consulting Eng.   5-Aug-99
P-3            Basement Plan                              4-Jun-99    2-Sep-99    AHA Consulting Eng.   5-Aug-99
P-4            First Floor Plan                           4-Jun-99    2-Sep-99    AHA Consulting Eng.   5-Aug-99
P-5            Second Floor Plan                          4-Jun-99    2-Sep-99    AHA Consulting Eng.   5-Aug-99
P-6            Third Floor Plan                           16-Jul-99   2-Sep-99    AHA Consulting Eng.   5-Aug-99
P-7            Roof  Plan                                 16-Jul-99   2-Sep-99    AHA Consulting Eng.   5-Aug-99
P-8            Riser Diagram                              16-Jul-99   2-Sep-99    AHA Consulting Eng.   5-Aug-99

GENERAL NOTES:
First set      4-Jun-99
Second Set     5-Aug-99

HVAC

H-1            HVAC Schedules, Notes and Legends          4-Jun-99    5-Aug-99    AHA Consulting Eng.
H-2            HVAC Details                               4-Jun-99    5-Aug-99    AHA Consulting Eng.
H-3            HVAC Basement Plan                         4-Jun-99    2-Sep-99    AHA Consulting Eng.
H-4            HVAC First Floor Plan                      4-Jun-99    5-Aug-99    AHA Consulting Eng.
H-5            HVAC Second Floor Plan                     4-Jun-99    5-Aug-99    AHA Consulting Eng.
H-6            HVAC Third Floor Plan                      4-Jun-99    5-Aug-99    AHA Consulting Eng.
H-7            HVAC Roof  Plan                            4-Jun-99    5-Aug-99    AHA Consulting Eng.


ELECTRICAL

E-1            Notes and Legands                          4-Jun-99    5-Aug-99    AHA Consulting Eng.
E-2            Lighting Fixture Schedule & Detail         4-Jun-99    5-Aug-99    AHA Consulting Eng.
E-3            Site Plan & Details                        4-Jun-99    5-Aug-99    AHA Consulting Eng.

</TABLE>


                                       52

<PAGE>

<TABLE>
<CAPTION>

DWG            TITLE                                      DATED       REC'D       ISSUED BY             COMMENTS

<S>            <C>                                        <C>         <C>         <C>                   <C>
E-4            Basement Lighting Plan                     4-Jun-99    9-Sep-99    AHA Consulting Eng.   5-Aug-99
E-5            Basement Power Plan                        4-Jun-99    2-Sep-99    AHA Consulting Eng.   5-Aug-99
E-6            First Floor Lighting Plan                  4-Jun-99    5-Aug-99    AHA Consulting Eng.
E-7            First Floor Power Plan                     4-Jun-99    5-Aug-99    AHA Consulting Eng.
E-8            Second Floor Lighting Plan                 4-Jun-99    5-Aug-99    AHA Consulting Eng.
E-9            Second Floor Power Plan                    4-Jun-99    4-Aug-99    AHA Consulting Eng.
E-10           Third Floor Lighting Plan                  4-Jun-99    5-Aug-99    AHA Consulting Eng.
E-11           Third Floor Power Plan                     4-Jun-99    5-Aug-99    AHA Consulting Eng.
E-12           Power Riser Diagram                        4-Jun-99    2-Sep-99    AHA Consulting Eng.   4-Jun-99
E-13           Electrical Schedules                       4-Jun-99    5-Aug-99    AHA Consulting Eng.
E-14           Electrical Schedules & Details             16-Jul-99   5-Aug-99    AHA Consulting Eng.

Specifications:

</TABLE>


                                       53

<PAGE>


                      EXHIBIT C -PERMITTED TITLE EXCEPTIONS

                  (a) Any and all present and future laws, regulations,
         restrictions, requirements, ordinances, resolutions and orders
         (including, without being limited to, any of the foregoing relating to
         zoning, building and environmental protection) as to the use,
         occupancy, subdivision or improvement of the Property adopted or
         imposed by any bureau, board, commission, legislature, department or
         other governmental body.

                  (b) The Contracts.

                  (c) Any state of facts existing as of the date of this
         Agreement which a personal inspection of the Property might disclose.

                  (d) Taxes, water charges, sewer rents and assessments, subject
         to adjustment as provided in this Agreement.

                  (e) Any lien or encumbrance encumbering the Property as to
         which Seller shall deliver to Purchaser, or Purchaser's title company,
         if any, at or prior to the Closing (or after the Closing in accordance
         with customary conveyancing practices), proper instruments, in
         recordable form, canceling such lien or encumbrance, together with any
         other instruments necessary thereto and the cost of recording and
         canceling the same.

                  (f) Variations between the tax lot lines and the record lines.

                  (g) Any Additional Exceptions that, pursuant to the terms of
         SECTION 10 of this Agreement, shall be or be deemed to be Permitted
         Title Exceptions.

                  (h) All matters set forth in First American Title Insurance
         Company Policy No. 20344472 other than those evidencing Financial
         Encumbrances.

                  (i) Proposed Easement and Maintenance Agreement between Seller
         and Massachusetts Wellness & Fitness, L.L.C.

                                        54

<PAGE>



                      EXHIBIT D - CONTRACTS AND AGREEMENTS

1.       Reciprocal Access and Utility Easement dated March 25, 1999 between
         Seller and Polaroid Corporation, filed with the South Registry District
         of Middlesex County as Document No. 1101665 and recorded with the
         Middlesex South District Registry of Deeds on March 26, 1999 as
         Instrument No. 503.

2.       Reciprocal Easement Agreement dated March 25, 1999 between Seller and
         Polaroid Corporation, filed with the South Registry District of
         Middlesex County as Document No. 1101666.

3.       Mutual Covenants agreement dated March 25, 1999 between Seller and
         Polaroid Corporation, filed with the South Registry District of
         Middlesex County as Document No. 1101667.

4.       Landscape License Agreement dated March 25, 1999 between Seller and
         Polaroid Corporation, filed with the South Registry District of
         Middlesex County as Document No. 1101668.

5.       Agreement regarding the apportionment of real estate taxes between
         Polaroid Corporation and Seller, a copy of which has been delivered to
         Purchaser.

                                       55

<PAGE>


                           EXHIBIT E - LIST OF PERMITS

                                       56

<PAGE>

/ /  Form A Approval - plans approved by City of Waltham Board of Survey and
     Planning 3/4/99

/ /  MEPA confirmation that no review is required - see advisory opinion from
     EOEA/MEPA office dated 3/5/99

/ /  DEP Division of Watershed Management - Negative Determination relative to
     the applicability of the NPDES program (i.e. proposed development does not
     constitute a storm water discharge within the ORW) - see letter dated
     7/2/99

/ /  Waltham Conservation Commission (Ch. 131) Negative Determination of
     Applicability - executed 7/6/99

/ /  DEP - Notification Prior to Construction or Demolition (7/16/99)

/ / City of Waltham Permit to Build - Site Preparation (7/12/99)

/ / City of Waltham Sewer Connection Permit

/ / City of Waltham Permit to Build - Construction of Office Building (8/25/99)

                                       57

<PAGE>


[Receipt of deposit of $1,000,000.00 into account of Brown, Rudnick, Freed &
Gesmer.

Photocopy of check in the amount of $1,000,000.00 from PRAECIS PHARMACEUTICALS
INCORPORATED to Brown, Rudnick, Freed & Gesmer signed by Malcolm L. Gefter and
Kevin F. McLaughlin.]


                                       58

<PAGE>

                            BEST PROPERTY FUND, L.P.
                         Bren Schreiber Properties, Inc.
                          125 Summer Street, Suite 1640
                                Boston, MA 02110

                                     January 14, 2000

PRAECIS PHARMACEUTICALS INCORPORATED
One Hampshire Street
Cambridge, MA  02139

Attention:  Mr. Kevin F. McLaughlin, Chief Financial Officer

RE:    LETTER AGREEMENT PURSUANT TO PROPERTY LOCATED AT 830 WINTER STREET,
       WALTHAM MA (THE "PROPERTY")

Dear Mr. McLaughlin:

                  Praecis Pharmaceuticals Incorporated ("Praecis") and Best
Property Fund, L.P. ("Best") have executed that certain Contract of Sale dated
January 14, 2000 (the "Contract") regarding the Property. Praecis and Best
mutually acknowledge the desirability of entering into a supplemental agreement
with respect to construction change orders by Praecis pursuant to current
construction being undertaken by Best at the Property.

                  The letter ("Letter Agreement") shall constitute an agreement
between Praecis and Best to proceed with reasonable diligence and good faith to
negotiate and execute a binding agreement pursuant to change orders (the "Change
Order Agreement") by February 7, 2000 ("Target Date"). The Change Order
Agreement may be a separate agreement or an amendment to the Contract as
determined by the parties. In no event shall failure of the parties to agree on
or enter into the Change Order Agreement serve to nullify, change, modify or
otherwise affect in any way the agreement between the parties in the Contract.

                                       BREN SCHREIBER PROPERTIES, INC., as agent
                                       for BEST PROPERTY FUND, L.P.

                                       By: /s/ D.S. Hall
                                           -------------------------------------
                                           Name:   David S. Hall
                                           Title:  Development Manager


                                       PRAECIS PHARMACEUTICALS, INCORPORATED

                                       By: /s/ Kevin McLaughlin
                                           -------------------------------------
                                            Name:   Kevin McLaughlin
                                            Title:  Senior Vice President &
                                                    Chief Financial Officer

CC:
E. Hershfield, Esq.
M. Glazer P.C.
L. Owens
M. Lentz
J. Kerrigan


<PAGE>



                       FIRST AMENDMENT TO CONTRACT OF SALE

         This first amendment ("FIRST AMENDMENT") is made as of February 7,
2000, by and among Best Property Fund, L.P., a Delaware limited partnership
("SELLER"); and Praecis Pharmaceuticals Incorporated, a Delaware corporation
("BUYER").

                               W I T N E S S E T H

         WHEREAS, Seller and Buyer have duly executed that certain Contract of
Sale dated as of January 14, 2000 in connection with certain property commonly
known as 830 Winter Street, Waltham, Massachusetts ("AGREEMENT"); and

         WHEREAS, Seller and Buyer desire to amend and modify the Agreement in
the manner set forth herein.

         NOW, THEREFORE, in consideration of the foregoing premises, and other
good and valuable consideration, the receipt and sufficiency of which hereby are
acknowledged, Seller and Buyer agree that the Agreement shall be and hereby is
amended as follows:

1.       EXHIBIT B of the Agreement is hereby deleted in its entirety and the
         "EXHIBIT B" attached hereto shall be substituted in its stead.

2.       Except as herein amended, the Agreement and all covenants, agreements,
         terms and conditions thereof shall remain and continue in full force
         and effect and hereby are in all respects ratified and confirmed.

3.       The covenants, agreements, terms and conditions of the First Amendment
         shall bind and inure to the benefit of the parties hereto and their
         respective successors and assigns.

4.       This First Amendment shall not be changed orally, but only by writing
         signed by the party against whom enforcement thereof is sought.

5.       This First Amendment may be executed in one or more counterparts, which
         collectively will constitute only one instrument.

                          [SEE SIGNATURES ON NEXT PAGE]

                                        2


<PAGE>



         IN WITNESS WHEREOF, the undersigned have executed this instrument under
seal as of the date first above written.

                                       SELLER:

                                       BEST PROPERTY FUND, L.P., a Delaware
                                       limited partnership

                                       By: BBS INVESTORS II,  a Delaware general
                                           partnership, its general partner

                                       By: SCHREIBER
                                           DEVELOPMENTS, LLC, a California
                                           limited liability company, a
                                           general partner

                                           By: /s/ C.J. Schreiber
                                               ---------------------------------
                                               Charles J. Schreiber, Jr.
                                               Manager

                                       PURCHASER:

                                       PRAECIS PHARMACEUTICALS
                                       INCORPORATED

                                       By: /s/ Kevin F. Mclaughlin
                                           -------------------------------------
                                           Name:  Kevin F. McLaughlin
                                           Title:  Sr. V.P. and C.F.O.

                                        3


<PAGE>



                                    EXHIBIT B

                                  SELLER'S WORK

I.       DEFINITIONS

         The following terms shall have the meanings specified in this Section
when used in this EXHIBIT B (the meanings specified are applicable to both the
singular and plural):

         "APPLICABLE LAWS" shall mean all applicable federal, state and local
laws, codes, ordinances, rules, regulations, standards or orders of any public
authority having jurisdiction over the Property, including building, health,
labor, safety, licensing, environmental or zoning laws, codes, ordinances,
rules, regulations, standards or orders of any such public authority.

         "ARCHITECT" shall mean Jung/Brannen Associates, Inc., who shall be
responsible for the design of the Seller's Work on behalf of Seller, pursuant to
the Design Contract (as hereinafter defined).

         "CONSTRUCTION CONTRACT" shall mean the construction contract dated as
of April 13, 1999 by and between Seller or its affiliates or agents and the
Contractor for the construction of the Seller's Work, as such construction
contract may be amended from time to time; provided, however, that no such
amendment shall affect Contractor's warranties set forth therein.

         "CONTRACTOR" shall mean John Moriaty & Associates, Inc., the general
contractor who will be responsible for constructing the Seller"s Work on behalf
of Seller pursuant to the Construction Contract.

         "CORRECTION COSTS" shall mean all costs and expenses, including without
limitation, all hard costs; construction management fees, remobilization fees
and other soft costs; and lost rent (calculated on an assumed rental of $400,000
per month) that Seller reasonably estimates would be incurred or suffered by
Seller if a Major Purchaser Initiated Change (hereinafter defined) is carried
out, Purchaser then does not purchase the Property and Seller then must
reconstitute the Improvements as an office building in accordance with the Plans
and Specifications. Such costs and expenses shall include, without limitation,
Seller's reasonable estimate of (i) all costs and expenses which would result
from the required removal of certain non-reusable components of the Improvements
which were added as a result of the Major Purchaser Initiated Change; (ii) all
costs and expenses which would result from the reincorporation into the
Improvements of certain components of the work set forth in the Plans and
Specifications which were deleted from the

                                       4

<PAGE>



Seller's Work as a result of the Major Purchaser Initiated Change; and (iii) all
lost rent Seller would suffer, at an assumed rate of $400,000 per month from (x)
the date which is sixty (60) days after the date on which Seller reasonably
estimates the Seller's Work would have been Finally Completed (as hereinafter
defined) if no Purchaser Initiated Change Orders (hereinafter defined) had been
executed and (y) the date on which Seller reasonably estimates the
reconstitution of the Improvements as an office building in accordance with the
Plans and Specifications would be Finally Complete (assuming that such
reconstitution would not begin until the day after the date of the Closing set
forth in this Agreement). Notwithstanding the foregoing, the portion of any such
delay which also is the subject of a Letter of Credit shall not be included in
the calculation of Correction Costs.

         "DESIGN CONTRACT" shall mean the design contract entered into by and
between Seller or its affiliates or agents and the Architect for the design of
the Seller's Work, as such design contract may be amended; provided, however,
that no such amendment shall affect Architect's warranties set forth therein.

         "EVENT OF FORCE MAJEURE" shall mean labor disputes, fire, unusual
delays in deliveries, unavoidable conditions or other causes beyond the
Contractor's control which the Architect determines may justify delay.

         "LETTER OF CREDIT" shall mean a letter of credit on terms and from an
issuing bank(s) acceptable to Seller and which otherwise satisfies the
requirements set forth herein.

         If the Letter of Credit is being issued in connection with a Time
Extending Purchaser Initiated Change (hereinafter defined), and the Time
Extending Purchaser Initiated Change, together with any then executed Purchaser
Initiated Change Orders, would, in Seller's reasonable estimation, result in a
cumulative delay in the Final Completion of the Seller's Work of more than sixty
(60) days from the date on which Seller reasonably estimates the Seller's Work
would have been Finally Completed if no Purchaser Initiated Change Orders had
been executed, then the Letter of Credit shall be in an amount equal to the
product of $13,333.00 multiplied by the number of days that Seller reasonably
estimates the Final Completion of the Seller's Work would be so delayed beyond
such sixty (60) day period.

         If the Letter of Credit is being issued in connection with a Major
Purchaser Initiated Change, then the Letter of Credit shall be in an amount
equal to the Correction Costs; plus, if the Major Purchaser Initiated Change,
together with any then executed Purchaser Initiated Change Orders, would, in
Seller's reasonable estimation, result in a cumulative delay in the Final
Completion of the Seller's Work of more than sixty (60) days from the date on
which Seller reasonably estimates the Seller's Work would have been Finally
Completed if no Purchaser

                                       5

<PAGE>



Initiated Change Orders had been executed, then the amount of the Letter of
Credit shall be increased by an amount equal to the product of $13,333.00
multiplied by the number of days that Seller reasonably estimates that the Final
Completion of the Seller's Work would be so delayed beyond such sixty (60) day
period.

         If the Closing occurs in accordance with the terms of this Agreement,
each such Letter of Credit shall be returned to Purchaser. If Purchaser defaults
in its obligations to purchase the Property under this Agreement, which default
would entitle Seller to retain the Deposit as liquidated damages, then Seller
may draw upon each Letter of Credit, and any funds drawn thereunder shall not be
part of the Deposit or applied against any liquidated damages to be paid to
Seller, shall be conclusively deemed to be fully earned by Seller and shall not
be subject to refund or offset under any circumstances. Seller may not draw upon
any Letter of Credit except as set forth in the preceding sentence.

         "PLANS AND SPECIFICATIONS" shall mean the drawings, plans and written
requirements prepared by the Architect or engineers or other consultants which
describe improvements to be constructed at the Property and which have been
delivered to Purchaser prior to the date of this Agreement, and which are listed
on SCHEDULE 1 hereto.

         "RECORD DRAWINGS" shall mean, collectively, the Plans and
Specifications, together with all Addenda (hereinafter defined) approved by
Seller, all Seller Initiated Change Orders (hereinafter defined) approved by
Seller and all Purchaser Initiated Change Orders (hereinafter defined) approved
by Seller.

         "SELLER'S WORK" shall mean all labor, materials, equipment and
services, or any portion thereof, that are indicated on or are reasonably
inferable from the Record Drawings, or that are required in accordance with any
Applicable Law now in effect including, but not limited to, all types and
quantities of components, items, systems, materials and methods of construction.

         "SUBCONTRACTOR" shall mean any subcontractor or supplier in privity
with the contractor at any tier.

II.      SELLER'S DUTIES AND RESPONSIBILITIES

         Seller shall be responsible for the following duties and
responsibilities:

         1.       Seller shall oversee the Contractor who shall cause the
                  Seller's Work to be constructed in accordance with the Record
                  Drawings.

                                       6

<PAGE>



         2.       Seller shall provide construction and design administration
                  services and coordinate all portions of the Seller's Work
                  (provided that Seller shall not have responsibility for or
                  have control over the construction means, methods, techniques,
                  sequences and procedures affecting the Seller's Work).

         3.       Seller shall take all other actions reasonably necessary to
                  perform its obligations as set forth in this EXHIBIT B.

         4.       Seller shall oversee the efforts of the Contractor who shall
                  establish and implement adequate procedures for processing
                  and approval of shop drawings, product data, samples and other
                  submittals.

         5.       Seller shall oversee the efforts of the Contractor who shall
                  maintain appropriate record copies of all subcontracts,
                  drawings, specifications, Addenda, Seller Initiated Change
                  Orders, Purchaser Initiated Change Orders and other
                  modifications in good order. Seller shall monitor the efforts
                  of the Contractor who shall mark-up the Plans and
                  Specifications to reflect changes as they occur which shall be
                  turned over to Seller upon completion of the Seller's Work.

         6.       Seller shall monitor the Contractor's management of the
                  performance of Subcontractors.

         7.       Seller shall coordinate inspections by the Architect with the
                  Contractor.

         8.       Seller shall coordinate the efforts of Purchaser, the
                  Architect and the contractor in Punch List compilation. Seller
                  shall monitor the efforts of the Contractor in the completion
                  of the Punch List items.

         9.       Seller shall secure from the Contractor all warranties and
                  guaranties for the benefit of Purchaser, manuals, Record
                  Drawings and keys upon final completion.

III.     INSPECTION AND ENTRY

         From and after the date of this Agreement, Purchaser and its agents
shall have the right to enter onto the Property from time to time during
construction to observe and inspect the Seller's Work; provided such entry shall
be at the sole risk of Purchaser and that Seller shall not be liable in any way
for any injury, loss or damage which may occur to any of the installations made
or to property placed therein or for any delay in the delivery of the Property
or the completion of the Seller's Work caused by such entry and installations.
Purchaser shall cooperate with Seller in all

                                       7

<PAGE>



respects and shall not interfere with construction activities of the Contractor
in connection with the completion of the Seller's Work, and Purchaser shall
immediately comply with any directive of Seller with respect to activities at
the Property.

IV.      CHANGES IN THE WORK

         1.       ADDENDA AND SELLER INITIATED CHANGE ORDERS

         Seller may approve addenda and minor changes and substitutions, such as
field changes to the Plans and Specifications proposed by Seller, Architect
and/or Contractor (collectively, "ADDENDA") and may approve change orders to the
Plans and Specifications proposed by Seller, Architect and/or Contractor
("SELLER INITIATED CHANGE ORDERS"); provided, however, that the same (A) do not
modify the Plans and Specifications in any material respect, unless Purchaser
has granted (or has been deemed to have granted) its prior written approval,
which may be granted or withheld in Purchaser's sole discretion; (B) do not
reduce the scope, quality, quantity, function or intent of Seller's Work as
specified in the Plans and Specifications, unless Purchaser has granted (or has
been deemed to have granted) its prior written approval, which may be granted or
withheld in Purchaser's sole discretion; and (C) do not otherwise change the
quality of the Seller's Work, unless Purchaser has granted (or has been deemed
to have granted) its prior written approval, which approval shall not be
unreasonably withheld or delayed. If Seller requests Purchaser's written
approval pursuant to this SECTION (IV)(1), Purchaser shall respond to any such
request within seven (7) days. If such response is a refusal to grant approval,
it shall contain Purchaser's reasons for refusing to grant the requested
approval. If Purchaser fails to respond to any such request for written approval
within seven (7) days period, as a result of such failure, Purchaser shall be
deemed to have granted its prior written approval as requested by Seller.

         2.       PURCHASER INITIATED CHANGE ORDERS

                  A.       Purchaser acknowledges that the Plans and
                           Specifications do not include tenant improvements,
                           amenity spaces, signs, directories, decorations,
                           fixtures or other upgrades. Except as otherwise
                           provided herein, no extra work (including, without
                           limitation, increases in the scope of the Seller's
                           Work) or changes in the Seller's Work requested by
                           Purchaser ("PURCHASER INITIATED CHANGE") shall be
                           made except in accordance with a duly issued written
                           change order executed by Seller and Purchase
                           authorizing such Purchaser Initiated Change
                           ("PURCHASER INITIATED CHANGE ORDER"), notwithstanding
                           the course of dealing between, or the course of
                           performance of, the parties or industry standards.

                                       8


<PAGE>



                  B.       If Purchaser, from time to time, requests a Purchaser
                           Initiated Change, Purchaser shall send Seller a
                           written notice, setting forth, in reasonable detail,
                           the changes in the Plans and Specifications, and the
                           changes in the scope of the Seller's Work, which
                           would be required by the Purchaser Initiated Change
                           (each, a "PURCHASER INITIATED CHANGE NOTICE").

                  C.       Within ten (10) business days after Seller receives a
                           purchaser Initiated Change Notice, Seller shall send
                           Purchaser a written notice (each a "SELLER PIC
                           RESPONSE NOTICE") specifying whether, in Seller's
                           reasonable determination, the Purchaser Initiated
                           Change described in the Purchaser Initiated Change
                           Notice is a "MINOR PURCHASER INITIATED CHANGE"
                           (hereinafter defined), a "MAJOR PURCHASER INITIATED
                           CHANGE" or a "TIME EXTENDING PURCHASER INITIATED
                           CHANGE." Each Seller PIC Response Notice shall
                           specify the reasons for Seller's determination.

                           A "Minor Purchaser Initiated Change" shall mean a
                           Purchaser Initiated Change which Seller determines,
                           in its reasonable discretion, (i) will not involve
                           the incorporation into the Seller's Work of any
                           components which will have to be removed in the event
                           the Property is not purchased by Purchaser in order
                           to reconstitute the Improvements as an office
                           building in accordance with the Plans and
                           Specifications; (ii) will not delay the Final
                           Completion of the Seller's Work; (iii) will not
                           require new licenses, permits or approvals or the
                           resubmission or modification of existing licenses,
                           permits or approvals; and (iv) will not involve the
                           removal of any component of the work set forth in the
                           Plans and Specifications which will need to be
                           reincorporated into the Improvements in the event the
                           Property is not purchased by Purchaser.

                           A "Major Purchaser Initiated Change" shall mean a
                           Purchaser Initiated Change which Seller determines,
                           in its reasonable discretion, (i) will involve the
                           incorporation into the Seller's Work of any component
                           which will have to be removed in the event the
                           Property is not purchased by Purchaser in order to
                           reconstitute the Improvements as an office building
                           in accordance with the Plans and Specifications; or
                           (ii) will delay the Final Completion of the Seller's
                           Work; or (iii) will require new licenses, permits or
                           approvals or the resubmission or modification of
                           existing licenses, permits or approvals; or (iv) will
                           involve the removal of any component of the work set
                           forth in the Plans and Specifications which will need
                           to be

                                       9

<PAGE>



                           reincorporated into the Improvements in the event the
                           Property is not purchased by Purchaser.

                           A "Time Extending Purchaser Initiated Change" shall
                           mean a Purchaser Initiated Change which Seller
                           determines, in its reasonable discretion, will delay
                           the Final Completion of the Seller's Work, but (i)
                           will not involve the incorporation into the Seller's
                           Work of any component which will have to be removed
                           in the event the Property is not purchased by
                           Purchaser in order to reconstitute the Improvements
                           as an office building in accordance with the Plans
                           and Specifications; (ii) will not require new
                           licenses, permits or approvals or the resubmission or
                           modification of existing licenses, permits or
                           approvals; and (iii) will not involve the removal of
                           any component of the work set forth in the Plans and
                           Specifications which will need to be reincorporated
                           into the Improvements in the event the Property is
                           not purchased by Purchaser.

                  D.       If a Seller PIC Response Notice indicates that a
                           Purchaser Initiated Change is a Minor Purchaser
                           Initiated Change, then said Seller PIC Response
                           Notice shall be accompanied by a proposed Purchaser
                           Initiated Change Order, which shall reflect (i) any
                           change (positive or negative) in the amount due to
                           the Contractor pursuant to the Construction Contract
                           as a result of the Minor Purchaser Initiated Change;
                           and (ii) any additional funds to be paid by Purchaser
                           in connection with such Minor Purchaser Initiated
                           Change, including, without limitation, all increased
                           construction management fees and other soft costs to
                           be incurred by Seller in connection with such Minor
                           Purchaser Initiated Change.

                           If Purchaser receives such a proposed Purchaser
                           Initiated Change Order, then Purchaser may elect
                           either (i) to cause Seller to carry out the changes
                           in the Seller's Work authorized in such proposed
                           Purchaser Initiated Change Order by executing such
                           proposed Purchaser Initiated Change order and
                           returning it to Seller within five (5) business days
                           after receipt, together with good funds equal to the
                           total of any positive change in the amount due to the
                           Contractor on account of such Purchaser Initiated
                           Change Order and any additional funds to be paid to
                           Seller, or (ii) to withdraw the applicable Minor
                           Purchaser Initiated Change.

                           If Purchaser does not so execute and deliver the
                           Purchaser Initiated Change Order and said funds, then
                           Purchaser shall be deemed to have

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                           withdrawn the applicable Minor Purchaser Initiated
                           Change. If Purchaser does so execute and deliver the
                           Purchaser Initiated Change Order and said funds,
                           then, upon receipt (y) Seller shall execute the
                           Purchaser Initiated Change Order, whereupon it shall
                           become effective, and (z) any funds paid to Seller
                           shall not be part of the Deposit or applied against
                           any liquidated damages to be paid to Seller, shall be
                           conclusively deemed to be fully earned by Seller when
                           the work to be performed pursuant to such Purchaser
                           Initiated Change Order is completed, and shall not be
                           subject to refund or offset under any other
                           circumstances, unless Seller defaults in its
                           obligations under this Agreement. If such Purchaser
                           Initiated Change Order indicates any negative change
                           in the amount due to the Contractor, then, at the
                           Closing, Purchase shall receive a credit against the
                           Purchase Price equal to such amount.

                  E.       If a Seller PIC Response Notice indicates that a
                           Purchaser Initiated Change is a Time Extending
                           Purchaser Initiated Change, then said Seller PIC
                           Response Notice either shall indicate that Seller has
                           elected, in its Sole discretion, not to carry out the
                           changes in the Seller's Work which would be required
                           by the Time Extending Purchaser Initiated Change or
                           shall be accompanied by a proposed Purchaser
                           Initiated Change Order. Any such proposed Purchaser
                           Initiated Change Order shall reflect (i) any change
                           (positive or negative) in the amount due to the
                           Contractor pursuant to the Construction Contract as a
                           result of the Time Extending Purchase Initiated
                           Change; (ii) any additional funds to be paid by
                           Purchaser in connection with such Time Extending
                           Purchaser Initiated Change, including, without
                           limitation, all increased construction management
                           fees and other soft costs to be incurred by Seller in
                           connection with such Time Extending Purchaser
                           Initiated Change; (iii) the delay in the Final
                           Completion of the Seller's Work which Seller
                           reasonably estimates will result from the Time
                           Extending Purchaser Initiated Change; and (iv)
                           whether a Letter of Credit must be provided in
                           connection with the Time Extending Purchaser
                           Initiated Change, and, if so, the amount of such
                           Letter of Credit. If Seller elects not to carry out
                           the Time Extending Purchaser Initiated Change, it
                           shall not be carried out.

                           If Purchaser receives such a proposed Purchaser
                           Initiated Change Order, then Purchaser may elect
                           either (i) to cause Seller to carry out the changes
                           in the Seller's work authorized in such proposed
                           Purchaser Initiated Change Order by executing such
                           proposed Purchaser Initiated Change

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                           Order and returning it to Seller within five (5)
                           business days after receipt, together with good funds
                           equal to the total of any positive change in the
                           amount due to the Contractor on account of such
                           Purchaser Initiated Change Order and any additional
                           funds to be paid to Seller, and together with any
                           Letter of Credit to be provided in connection with
                           the Purchaser Initiated Change Order, or (ii) to
                           withdraw the applicable Time Extending Purchaser
                           Initiated Change.

                           If Purchaser does not so execute and deliver the
                           Purchaser Initiated Change Order, said funds and any
                           applicable Letter of Credit, then Purchaser shall be
                           deemed to have withdrawn the applicable Time
                           Extending Purchaser Initiated Change. If Purchaser
                           does so execute and deliver the Purchaser Initiated
                           Change Order, said funds and any applicable Letter of
                           Credit, then, upon receipt (x) Seller shall execute
                           the Purchaser Initiated Change Order, whereupon it
                           shall become effective, (y) any funds paid to Seller
                           shall not be part of the Deposit or applied against
                           any liquidated damages to be paid to Seller, shall be
                           conclusively deemed to be fully earned by Seller when
                           the work to be performed pursuant to such Purchaser
                           Initiated Change Order is completed, and shall not be
                           subject to refund or offset under any other
                           circumstances, unless Seller default in its
                           obligations under this Agreement, and (z) any Letter
                           of Credit and any funds resulting therefrom shall be
                           retained by Seller in accordance with the provisions
                           set forth in the definition of "Letter of Credit" in
                           this EXHIBIT B. If such Purchaser Initiated Change
                           Order indicates any negative change in the amount
                           due to the Contractor, then, at the Closing,
                           Purchaser shall receive a credit against the Purchase
                           Price equal to such amount.

                  F.       If a Seller PIC Response Notice indicates that a
                           Purchaser Initiated Change is a Major Purchaser
                           Initiated Change, then said Seller PIC Response
                           Notice either shall indicate that Seller has elected,
                           in its sole discretion, not to carry out the changes
                           in the Seller's Work which would be required by the
                           Major Purchaser Initiated Change (provided, however,
                           that this option to not carry out such changes only
                           shall be available to Seller if Seller determines, in
                           its reasonable discretion, that the Major Purchaser
                           Initiated Change will delay the Final Completion of
                           the Seller's Work or will require new licenses,
                           permits or approvals or the resubmission or
                           modification of existing licenses, permits or
                           approvals) or shall be accompanied by a proposed
                           Purchaser Initiated Change Order. If


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                           Seller elects not to carry out the Major Purchase
                           Initiated Change Order, it shall not be carried out.
                           Any such Proposed Purchaser Initiated Change Order
                           shall reflect (i) any change (positive or negative)
                           in the amount due to the Contractor pursuant to the
                           Construction Contract as a result of the Major
                           Purchaser Initiated Change; (ii) any additional funds
                           to be paid by Purchaser in connection with such Major
                           Purchaser Initiated Change, including, without
                           limitation, all increased construction management
                           fees and other soft costs incurred by Seller in
                           connection with such Major Purchaser Initiated
                           Change; (iii) the delay, if any, in the Final
                           Completion of the Seller's Work which Seller
                           reasonably estimates will result from the Major
                           Purchaser Initiated Change; and (v) the amount of the
                           Letter of Credit to be provided in connection with
                           the Major Purchaser Initiated Change.

                           If Purchaser receives such a proposed Purchaser
                           Initiated Change Order, then Purchaser may elect
                           either (i) to cause Seller to carry out the changes
                           in the Seller's Work authorized in such proposed
                           Purchaser Initiated Change Order and returning it to
                           Seller within five (5) business days after receipt,
                           together with good funds equal to the total of any
                           positive change in the amount due to the Contractor
                           on account of such Purchaser Initiated Change Order
                           and any additional funds to be paid to Seller, and
                           together with the Letter of Credit to be provided in
                           connection with the Purchaser Initiated Change Order
                           or (ii) to withdraw the applicable Major Purchaser
                           Initiated Change.

                           If Purchaser does not execute and deliver the
                           Purchaser Initiated Change Order, said funds and the
                           applicable Letter of Credit, then Purchaser shall be
                           deemed to have withdrawn the applicable Major
                           Purchaser Initiated Change. If Purchaser does so
                           execute and deliver the Purchaser Initiated Change
                           Order, said funds and the applicable Letter of
                           Credit, then, upon receipt, (x) Seller shall execute
                           the Purchaser Initiated Change Order, whereupon it
                           shall become effective, (y) any funds paid to Seller
                           shall not be part of the Deposit or applied against
                           any liquidated damages to be paid to Seller, shall be
                           conclusively deemed to be fully earned by Seller when
                           the work to be performed pursuant to such Purchaser
                           Initiated Change Order is completed, and shall not be
                           subject to refund or offset under any other
                           circumstances, unless Seller defaults in its
                           obligations under this Agreement, and (z) the Letter
                           of Credit and any funds resulting therefrom, shall be
                           retained by Seller in accordance with the provisions
                           set forth in

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<PAGE>



                           the definition of "Letter of Credit" in this EXHIBIT
                           B. If such Purchaser Initiated Change Order indicates
                           any negative change in the amount due to the
                           Contractor, then, at the Closing, Purchaser shall
                           receive a credit against the Purchase Price equal to
                           such amount.

V.       CHANGES IN SCHEDULE

         1.       SCHEDULE

         Seller has provided Purchaser with a construction schedule, prepared by
the Contractor, detailing the scheduling and timing of the Seller's Work, and
indicting a Final Completion date prior to September 1, 2000 ("SCHEDULE"), it
being understood that the Schedule shall be updated by Seller from time to time
to reflect the actual progress of constructions.

         2.       SUBSTANTIAL COMPLETION

         Seller shall provide Purchaser not less than sixty (60) days prior
written notice of the anticipated date of Final Completion (herein defined).
When Seller has achieved Substantial Completion (as defined in the Construction
Contract) of the Seller's Work, Seller shall cause the Architect to issue a
certificate of Substantial Completion with a copy to Purchaser. No later than
two (2) Business Days following Purchaser's receipt of such certificate of
Substantial Completion, Purchaser and Seller shall jointly inspect the Seller's
Work with the Architect. No later than three (3) Business Days after such
inspection, the Architect shall prepare a list of all purported non-deminimus
discrepancies between the Record Drawings and the Seller's Work as constructed
("PUNCH LIST"), and shall deliver such list to Seller and Purchaser. If Seller
or Purchaser contest the inclusion of any item in, or the omission of any item
from, the Punch list, then during the next four (4) Business Day period, Seller,
Purchaser and the Architect shall cooperate in good faith to finalize the Punch
list. In the event that despite such cooperation, Seller, Purchaser and the
Architect are unable to finalize the Punch List, then any disputes regarding the
inclusion of any item in, or the omission of any item from, the Punch List shall
be determined as follows: (A) disputes involving items having a cumulative
value, as estimated by the Architect, not in excess of $25,000, shall be
determined by architect within five (5) Business Days following such four (4)
Business Day period. (B) Disputes involving items having a cumulative value as
estimated by the Architect, in excess of $25,000, shall be determined within
five (5) Business Days following such four (4) Business Day period by Peter
Barber, presently of Northland Development Corporation ("INITIAL ARBITRATOR")
or Robert M. Keeley, presently of Diversified Project Management ("SECONDARY
ARBITRATOR"), if the Initial Arbitrator is not available. The architect shall
submit matters to the Initial Arbitrator and Secondary Arbitrator. All decisions
of the Architect, Initial Arbitrator and Secondary Arbitrator pursuant to this
SECTION V(2) shall be

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<PAGE>



binding and conclusive. After the Punch List is finalized pursuant to this
SECTION V(2), Seller shall proceed to cause the Punch List to be completed as
soon as reasonably practicable after Substantial Completion. All costs and
expenses incurred with respect to the Initial Arbitrator or the Secondary
Arbitrator shall be shared equally between Seller and Buyer.

         3.       FINAL COMPLETION

         "Final Completion" (and derivations thereof) of the Seller's Work shall
mean the date on which the last of the following shall have occurred:

         (a)      The completion of the Punch List, as certified by the
                  Architect.

         (b)      The submission to Purchaser by the Seller of the Record
                  Drawings for the Seller's Work, along with all warranties and
                  guaranties, manuals and keys.

         (c)      The submission to Purchaser by the Seller of final lien
                  releases and waivers from the Contractor and, if available,
                  all major Subcontractors, which releases and waivers may be
                  conditioned on receipt of amounts due from Seller upon final
                  completion of the Seller's Work.

         (d)      The removal from the Property by Seller of temporary
                  facilities, tools and similar items.

         (e)      The issuance by the City of Waltham of a core and shell
                  certificate of occupancy for the Seller's Work.

         Upon Final Completion, Seller shall notify Purchaser of the Closing
Date in accordance with SECTION 4 of the Agreement.

VI.      FINAL COMPLETION DATE

                  A.       The Seller agrees to use commercially diligent
                           efforts to cause Final Completion of the Seller's
                           Work to be achieved on or before September 1, 2000,
                           subject to Events of Force Majeure and Purchaser
                           Initiated Change Orders.

                  B.       If Final Completion is not achieved on or before
                           September 1, 2000 (which date shall be extended for
                           up to sixty (60) days for each day that the
                           construction of the Seller's Work was delayed because
                           of an Event of

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<PAGE>


                           Force Majeure and which date also shall be extended
                           by one day for each day that the construction of the
                           Seller's Work was delayed due to Pur chaser Initiated
                           Orders), then, as Purchaser's sole remedy on account
                           of such delay (other than Purchaser's termination
                           right set forth in SECTION 4 of this Agreement) for
                           each day thereafter until Final Completion is
                           achieved, the Purchase Price shall be reduced by
                           $5,000 per day, provided, however, that if Purchaser
                           shall elect not to exercise its right to terminate
                           this Agreement as of December 31, 2000 (or such later
                           date as Purchaser shall have the right to terminate
                           this Agreement on account of Purchaser Initiated
                           Change Orders), all as described in SECTION 4 of this
                           Agreement, then the $5,000 per day reduction in the
                           Purchase Price shall be tolled for thirty (30) days
                           following Purchaser's election (or deemed election)
                           not so to terminate this Agreement. Purchaser shall
                           not lose the benefit of any Purchase Price reduction
                           that already shall have accrued, and the $5,000 per
                           day reduction shall recommence to accrue following
                           such thirty (30) day period if Seller shall not then
                           have achieved Final Completion of the Seller's Work.