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                                                                   Exhibit 10.23

                     PARTNERSHIP INTEREST PURCHASE AGREEMENT

      THIS PARTNERSHIP INTEREST PURCHASE AGREEMENT (this "PURCHASE AGREEMENT")
is made and entered into this 3rd day of August, 2001 (the "EFFECTIVE DATE"), by
and between MADEIRA-RMC L.P., a New York limited partnership (the
"Partnership"), MADEIRA MANAGEMENT COMPANY, INC., a Delaware corporation
("MADEIRA"), MERLOT MANAGEMENT COMPANY, INC., a Delaware corporation ("MERLOT")
(Madeira and Merlot are collectively referred to herein as the "SELLERS"),
ROBERT MARTIN COMPANY, LLC, a New York limited liability company, f/k/a Robert
Martin Company, a New York general partnership ("RMC"), and RMC as agent for 5/6
Skyline Realty L.L.C., a New York limited liability company ("PURCHASER").

      WHEREAS, the Partnership is a limited partnership duly organized, validly
existing, and in good standing under the laws of the State of New York;

      WHEREAS, the Partnership owns certain real property located in Westchester
County, New York, commonly known as No. 5 and No. 6 Skyline Drive,
Mid-Westchester Executive Park, Westchester, New York, as more fully described
in EXHIBIT A attached hereto and made a part hereof;

      WHEREAS, Merlot owns a forty-nine and seven tenths percent (49.7%) general
partnership interest and Madeira owns a twenty and three tenths percent (20.3%)
general partnership interest and RMC owns a thirty percent (30%) limited
partnership interest in the Partnership;

      WHEREAS, the partners in the Partnership are implementing the buy/sell
provisions of section 8.01 of the Partnership's Amended and Restated Agreement
of Limited Partnership dated as of September 1, 1994 (the "Partnership
Agreement") pursuant to the terms of this Agreement;

      WHEREAS, Madeira and Merlot have initiated the buy/sell provisions by
sending a Purchase Offer (as defined in the Partnership Agreement) dated March
8, 2001 (the "Offer Date") to RMC, and the parties have thereafter determined
that Madeira and Merlot are the Sellers and RMC, as agent for 5/6 Skyline Realty
L.L.C., is the Purchaser;

      WHEREAS, Purchaser desires to purchase from Sellers, and Sellers desire to
sell to Purchaser, all of Sellers' rights, title, and interest in the
Partnership (the "INTEREST"); and

      WHEREAS, the purchase of the Interest by Purchaser shall occur in
accordance with the terms and conditions specified herein.

      NOW, THEREFORE, in consideration of the premises and the mutual covenants
contained herein, and the other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

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        1. PURCHASE AND SALE OF INTEREST.

              a. Upon the terms and conditions hereinafter set forth, Sellers
agree to sell, grant and convey, and Purchaser agrees to purchase and accept,
the Interest (as defined in the Recitals to this Purchase Agreement) for the
amount set forth below, free and clear of all liens, charges, restrictions,
encumbrances and security interests of any kind. After the purchase of the
Interest, RMC and Purchaser shall collectively hold one hundred percent
(100%) of the partnership interests in the Partnership.

              b. The net purchase price for the Interest following the
payment of Partnership debts and obligations and subject to adjustments and
prorations as provided for herein shall be Five Million Seven Hundred
Seventy-Three Thousand, Eight Hundred Thirty-One and 70/100 Dollars
($5,773,831.70) (the "PURCHASE PRICE") in cash, by bank wire transfer of
immediately available federal funds. The methodology for determining the
Purchase Price is attached hereto as EXHIBIT B.

              c. Sellers acknowledge that Purchaser is acquiring the Interest
to own, as of the Closing, the following (collectively, the "PROPERTY"):

               (i) that certain real property located in Westchester County, New
       York, commonly known as No. 5 and No. 6 Skyline Drive, Mid-Westchester
       Executive Park, Westchester, New York, as more fully described in EXHIBIT
       A attached hereto and made a part hereof (hereinafter referred to as the
       "LAND"), together with all improvements situated thereon (the
       "IMPROVEMENTS"), all fixtures used in the operation of the Land or the
       Improvements, and all other appurtenances to the Land;

               (ii) all personal property located on the Land and all supplies
       and inventory and replacements thereof now or hereafter affixed to and/or
       located at the Land and used in connection with the ownership,
       management, operation, maintenance or repair of the Land and the
       Improvements (collectively, the "PERSONAL PROPERTY"); and

               (iii) all intangible property relating to the Land, Improvements
       or the Personal Property, including, without limitation, the following
       (collectively, the "INTANGIBLE PROPERTY"): (A) all contracts and
       agreements, documents and instruments, including, without limitation, all
       leasing, service, warranty, guaranty, management, supply, employment, and
       maintenance agreements relating to, or required in connection with, the
       full use, operation, occupancy, ownership and enjoyment of the Land, the
       Improvements or the Personal Property or the business operations of the
       Partnership (collectively, the "AGREEMENTS"); (B) all certificates,
       permits, licenses, approvals or other authorizations required in
       connection with the ownership, use, operation or maintenance of the Land,
       the Improvements or the Personal Property or the business operations of
       the Partnership, and any future development or redevelopment thereof,
       from any governmental or quasi-governmental authority having jurisdiction
       over the Land or the Partnership (collectively, the "PERMITS AND
       LICENSES"); and (C) all right, title and interest in all warranties,
       plans and specifications for the Improvements and all tenant spaces,
       trade names, and development rights related to the business operations of
       the Partnership, the Land, the Improvements or the Personal Property.

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        2. INDEBTEDNESS OF THE PARTNERSHIP.

              a. The Partnership is indebted to Madeira and Merlot in the
principal amount of Six Million Two Hundred Sixty Thousand, Four Hundred
Thirty-Four and no/100 Dollars ($6,260,434) together with interest thereon in
the amount of Two Hundred Thirty-One Thousand Two Hundred Thirty-Five and no/100
Dollars ($231,235) as of the Closing Date (the "Partnership Indebtedness").

              b. Thereafter, at Closing Purchaser shall pay on behalf of the
Partnership any Partnership Indebtedness. Such payments shall be made 71% to
Merlot and 29% to Madeira.

        3. INDEBTEDNESS OF RMC.

              a. RMC is indebted to Madeira and Merlot in the principal amount
of Eight Hundred Fifty-Four Thousand, Four Hundred Ninety-Six and no/100 Dollars
($854,496) together with interest thereon in the amount of Eight Hundred
Forty-Seven Thousand, Eight Hundred Seventy-Eight and no/100 Dollars ($847,878)
as of the Closing Date (the "RMC Indebtedness").

              b. At Closing (as defined below), Purchaser shall pay the RMC
Indebtedness to Madeira and Merlot in cash, wire transfer or other readily
available funds. Such payments shall be made 71% to Merlot and 29% to Madeira.

        4. CLOSING DATE. The date on which the Closing shall occur (the
"CLOSING DATE") shall be August 2, 2001.

        5. CONDITIONS TO CLOSING.

              a. Purchaser's obligation to consummate the transactions
contemplated by this Purchase Agreement is subject to the following conditions:

                     (i) The representations and warranties of Sellers contained
              in this Agreement shall be true and correct on, and as of, the
              Closing Date, in all material respects, as though such
              representations and warranties were made on, and as of, such date.

                     (ii) From the Effective Date until the time of the Closing,
              there shall not have occurred any material and adverse change in
              the physical condition of the Property, except: (A) those changes
              caused by ordinary wear and tear; or (B) as caused directly or
              indirectly by any act or omission of Purchaser or its
              representatives, agents or employees.

                     (iii) Since the Effective Date, the operations of the
              Partnership shall have been carried out in the ordinary course of
              business and there shall not have occurred:

                            (1)    any material and adverse change in the
                                   condition (financial or otherwise) or in the
                                   overall business of the Partnership;

                            (2)    any material increase in the liabilities of
                                   the Partnership from

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                                   those liabilities listed or otherwise
                                   disclosed in the financial statements of the
                                   Partnership for the year ended December 31,
                                   2000 (the "Financial Statements"), other
                                   than those contemplated by this Agreement;
                                   and

                            (3)    any damage, destruction or loss (whether or
                                   not covered by insurance) materially and
                                   adversely affecting the Partnership.

                     (iv) Sellers shall have performed and complied with all of
              the terms, covenants, conditions and obligations of this Purchase
              Agreement, including, without limitation, the delivery
              requirements of Section 9(f) herein.

              b. Sellers' obligations to consummate the transactions
contemplated by this Purchase Agreement are subject to the following conditions:

                     (i) The representations and warranties of Purchaser
              contained in this Agreement shall be true and correct on, and as
              of, the Closing Date, in all material respects, as though such
              representations and warranties were made on, and as of, such date.

                     (ii) Purchaser shall have performed and complied with all
              of the terms, covenants, conditions and obligations of this
              Purchase Agreement, including without limitation, the delivery
              requirements of Section 9(e) herein.

                     (iii) Closing of the Debt Capitalization and Liquidating
              Distribution Agreement of even date herewith among Michaelson-RMC
              L.P., Michaelson Management Company, Inc., Michelin Management
              Company, Inc., RMC, and La Reserve Apartment-Hotel Corp.

                     (iv) Satisfaction of the RMC Indebtedness and evidence
              representing same.

                     (v) Satisfaction of the Partnership Indebtedness and
              evidence representing same.

              c. Purchaser may waive in writing any condition set forth in
Paragraph 5(a) and Sellers may waive in writing any condition set forth in
Paragraph 5(b) and require the other to effect the Closing pursuant to Paragraph
9.

      6. MUTUAL REPRESENTATIONS AND WARRANTIES. Sellers, RMC and Purchaser,
respectively, hereby represent and warrant to the others that the following are
true, accurate and complete as of the Effective Date and shall be true, accurate
and complete as of the Closing Date:

              a. Each of the Sellers, RMC and Purchaser, respectively, has the
full legal power and authority to enter into and perform this Purchase Agreement
in accordance with its terms. The execution and delivery of this Purchase
Agreement and the performance by each of the Sellers, RMC and

                                       -4-
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Purchaser, respectively, of its obligations hereunder requires no further
action or approval by either of the Sellers, RMC or Purchaser or any other
person or entity. This Purchase Agreement is the binding obligation of each
of Sellers, RMC and Purchaser.

              b. The execution, delivery and performance of this Purchase
Agreement and all documents in connection therewith are not in contravention of
or in conflict with any deed of trust, agreement or undertaking to which either
of the Sellers, RMC or Purchaser, respectively, is a party or by which either of
the Sellers, RMC or Purchaser, respectively, or any of their respective property
or assets, including the Property and the Interest, may be bound or affected.

      7. SELLERS' REPRESENTATIONS AND WARRANTIES. Sellers hereby represent and
warrant to the Purchaser that the following are true, accurate and complete as
of the Effective Date and shall be true, accurate and complete as of the Closing
Date:

              a. No bankruptcy, insolvency, rearrangement or similar action or
proceeding, whether voluntary or involuntary, is pending or, to the best of
either Seller's knowledge, threatened against either Seller.

              b. Each Seller is the owner of its Interest and has not pledged,
sold, transferred or hypothecated its Interest except as provided herein.

              c. There is no action, claim, demand, litigation, proceeding or
governmental investigation, at law or in equity, pending or, to the best of
either Seller's knowledge, threatened against or related to the Property or the
Partnership.

      8. DAMAGE, DESTRUCTION AND CONDEMNATION. In the event of any fire or other
casualty costing more than Three Million Dollars to repair or in the event any
condemnation proceedings are instituted with respect to all or more than 25% of
the rentable area of the Property prior to the Closing, Purchaser shall have the
right to terminate this Purchase Agreement by written notice to either of the
Sellers no later than the date that is fifteen (15) days after notice of such
event. The Closing Date shall, if necessary, be extended to coincide with the
expiration of such fifteen (15) day period.

      9. CLOSING.

              a. The Closing (the "CLOSING") shall be held on the Closing Date
in the offices of UBS Realty Investors LLC, 10 East 50th Street, New York, New
York, or at any other location mutually acceptable to the parties hereto.

              b. At the Closing, the parties shall apportion the real estate
taxes, utilities, rents and other expenses incurred or income received from the
Property as of the Closing Date in an equitable manner. Such taxes, utilities,
rents, other expenses shall be treated as a separate line item on the settlement
sheet at Closing and shall be netted together and satisfied by a separate
payment by either the Seller or Purchaser whichever of them shall be determined
to have a net payment obligation to the other hereunder. Rents received from
tenants of the Property after Closing shall be applied first to rent due during
the then current month and then to any rent accrued and unpaid as of the Closing
in which case

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70% of such rents shall be paid to Sellers and the balance to Purchaser. Any
transfer taxes, shall be paid by Sellers. RMC shall prepare and file any
transfer tax returns required to be filed, and Sellers shall duly and timely
execute any such returns, in respect of the purchase hereunder.

              c. At the Closing, Purchaser shall pay to Sellers the Purchase
Price and the RMC Indebtedness.

              d. At the Closing, the Partnership shall pay to Sellers the
Partnership Indebtedness.

              e. At the Closing, Purchaser shall execute and deliver to Sellers,
in form and substance reasonably satisfactory to Sellers' counsel, the
following:

                     (i) Certificate of dissolution of the Partnership.

                     (ii) Notices to tenants and service providers of the
              Property regarding the change in ownership of the Property
              reasonably acceptable to the parties.

                     (iii) Such other documents, forms, and other items as may
              be requested by Sellers or their counsel and as may be reasonably
              and customarily required to close similar transactions.

              f. At the Closing, Sellers shall execute and deliver, or cause the
Partnership to execute and deliver, to Purchaser, in form and substance
reasonably satisfactory to Purchaser's counsel, the following:

                     (i) Instructions to the Partnership to register on the
              Partnership's books and records the transfer of the Interest from
              Sellers to Purchaser.

                     (ii) FIRPTA affidavit.

                     (iii) Such other documents, forms and other items as may be
              requested by Purchaser or its counsel and may be reasonably and
              customarily required to close similar transactions.

                     (iv) The originals of all notes duly marked "paid in full"
              or other language of similar import in respect of the Partnership
              Indebtedness and RMC Indebtedness and/or such other evidence of
              satisfaction of the Partnership Indebtedness and RMC Indebtedness
              as Purchaser may reasonably request.

              g. As soon as practicable after Closing, Purchaser shall execute
and deliver to Sellers, in form and substance reasonably satisfactory to
Sellers' counsel, a final accounting of all activities of the Partnership as of
the Closing Date and Sellers' share of all such activities and the parties shall
reprorate, if necessary, the closing adjustments to reflect final accounting of
the property for 2001.

                                       -6-
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      10. INDEMNITY.

              a. Sellers and Purchaser shall indemnify, defend and hold the
other harmless from and against, and shall reimburse the other with respect to,
any and all claims, demands, causes of action, losses, damages, liabilities,
costs and expenses (including reasonable attorneys' fees and court costs,
whether suit is instituted or not), asserted against or actually incurred by the
indemnified party by reason of or arising out of the discovery following the
Closing of the breach or material misstatement by the indemnifying party of any
representation, warranty or covenant contained in this Purchase Agreement.

              b. RMC and Purchaser shall indemnify, defend and hold Sellers
harmless from and against, and shall reimburse the Sellers with respect to, any
and all claims, demands, causes of action, losses, damages, liabilities, costs
and expenses (including reasonable attorneys' fees and court costs, whether suit
is instituted or not), asserted against or actually incurred by the indemnified
parties after the Closing Date by reason of or arising out of the acts or
omissions of the Partnership or otherwise relating to the Partnership after the
Closing Date or the Property after the Closing Date.

              c. Subject to the last sentence of this section, Sellers shall
indemnify, defend and hold RMC and Purchaser harmless from and against, and
shall reimburse RMC and Purchaser with respect to, any and all claims, demands,
causes of action, losses, damages, liabilities, costs and expenses (including
reasonable attorneys' fees and court costs, whether suit is instituted or not),
asserted against or actually incurred by the indemnified parties after the
Closing Date by reason of or arising out of the acts or omissions of the
Partnership or otherwise relating to the Partnership prior to the Closing Date
or the Property prior to the Closing Date. In the event of a third party claim
against the Partnership arising out of circumstances occurring prior to the
Closing Date and the Purchaser pays or compromises such claim, Sellers shall be
responsible to Purchaser for such costs on a 70 to 30 basis with RMC's liability
capped at $760,445.

              d. The indemnified party must give the indemnifying party notice
of the indemnified claim within one year from the Closing in order to avail
itself of the remedies provided in this section.

      11. PRE-CLOSING REMEDIES.

              a. In the event of a breach or threatened breach of this Agreement
by either party, the non-breaching party shall have all rights and remedies that
may be available at law or equity or the Partnership Agreement.

      12. BROKERAGE.

              a. Except as otherwise disclosed in writing to Purchaser, Sellers
warrant to Purchaser and RMC that no broker is entitled to any brokerage
commission or fee arising out of this transaction, and Sellers shall indemnify,
hold and defend Purchaser and RMC harmless against any losses, liabilities,
expenses and claims resulting from a breach of the foregoing warranty.

              b. Except as otherwise disclosed in writing to Sellers, Purchaser
and RMC warrant to Sellers that no broker is entitled to any brokerage
commission or fee arising out of this transaction, and

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Purchaser and RMC shall indemnify, hold and defend Sellers harmless against any
losses, liabilities, expenses and claims resulting from a breach of the
foregoing warranty.

      13. GENERAL PROVISIONS.

              a. The terms and conditions of this Purchase Agreement shall be
binding upon, and inure to the benefit of, the parties hereto and their
respective heirs, successors, permitted assigns and legal representatives.

              b. The parties agree to take such further actions and to cause the
Partnership to take such actions as may be necessary in order to consummate the
transactions contemplated by this Purchase Agreement.

              c. The representations, warranties and indemnities of Sellers
contained in this Purchase Agreement or in any instrument, document or agreement
delivered by Sellers pursuant hereto shall survive the consummation of the
transfer of the Interest, and shall not be merged therein.

              d. Any notice required or permitted hereunder shall be deemed to
have been received either: (i) when delivered by hand to Purchaser or one of the
Sellers as evidenced by a signed receipt therefor; or (ii) when delivered by the
United States postal service, postage prepaid, or by a recognized commercial air
or local courier service, addressed as follows (or addressed in such other
manner as the party being notified shall have requested by such written notice
to the other party), except that refusal to accept delivery of notice shall be
deemed to be receipt hereunder:

              If to Madeira or Merlot:

              c/o UBS Realty Investors LLC
              10 East 50th Street, 15th floor
              New York, New York 10022
              Attn:  Scott M. Dalrymple

with a copy (which copy shall not constitute notice) to:

              Patton Boggs LLP
              2550 M Street, NW
              Washington, D.C. 20037
              Attn:  Ross E. Eichberg, Esq.

              If to RMC:

              Robert Martin Company, LLC
              100 Clearbrook Road
              Elmsford, NY  10523
              Attn:  Martin S. Berger

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              with a copy (which copy shall not constitute notice) to:

              Robert Martin Company, LLC
              100 Clearbrook Road
              Elmsford, NY  10523
              Attn:  Lloyd Roos

              e. This Purchase Agreement constitutes the entire agreement
between the parties concerning the subject matter hereof and otherwise
supersedes all prior agreements or undertakings with respect to each and every
provision of this Purchase Agreement.

              f. In the event that any one or more of the provisions contained
in this Purchase Agreement are held to be invalid, illegal or unenforceable in
any respect, such invalidity, illegality or unenforceability shall not affect
any other provision hereof, and this Purchase Agreement shall be construed as if
such invalid, illegal or unenforceable provision had not been contained herein.

              g. Any paragraph heading contained in this Purchase Agreement
shall be for convenience of reference only and shall not affect the construction
or interpretation of any provision of this Purchase Agreement.

              h. No failure by Purchaser, Sellers or the Partnership to insist
upon the strict performance of any term of this Purchase Agreement shall
constitute a waiver of any such breach or any subsequent breach of any such
term. No term of this Purchase Agreement and no breach thereof shall be waived,
altered or modified except by written instrument. No waiver of any breach shall
affect or alter this Purchase Agreement, but each and every term of this
Purchase Agreement shall continue in full force and effect with respect to any
other then existing or subsequent breach thereof.

              i. This Purchase Agreement shall be governed by and construed
according to the laws of the State of New York.

              j. This Purchase Agreement may not be assigned without the express
written consent of the other party, provided, however, that Purchaser shall have
the right, after notice and without the consent of Sellers, to assign his
interest in the Purchase Agreement to an entity controlled by Purchaser or to a
trust benefiting members of Purchaser's family.

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      IN WITNESS WHEREOF, the parties hereto have executed this Purchase
Agreement under seal as of the date first written above.

MADEIRA-RMC L.P.

BY:      MADEIRA MANAGEMENT COMPANY, INC.,
         its managing general partner

         By: /s/  Stephen J. Spey             (Seal)
            ---------------------------------
         Name:    Stephen J. Spey
            ---------------------------------
         Its:     Vice President
            ---------------------------------

MADEIRA MANAGEMENT COMPANY, INC.

         By: /s/  Stephen J. Spey             (Seal)
            ---------------------------------
         Name:    Stephen J. Spey
            ---------------------------------
         Its:     Vice President
            ---------------------------------

MERLOT MANAGEMENT COMPANY, INC.

         By: /s/  Stephen J. Spey             (Seal)
            ---------------------------------
         Name:    Stephen J. Spey
            ---------------------------------
         Its:     Vice President
            ---------------------------------

ROBERT MARTIN COMPANY, LLC                   ROBERT MARTIN COMPANY, LLC,
                                             AS AGENT FOR
                                             5/6 SKYLINE REALTY L.L.C.

By:      /s/ Robert F. Weinberg     (Seal)   By: /s/ Robert F. Weinberg   (Seal)
     -------------------------------            ---------------------------
         Robert F. Weinberg, Manager            Robert F. Weinberg, Manager

By:    /s/ Martin S. Berger         (Seal)   By: /s/ Martin S. Berger     (Seal)
     -------------------------------             --------------------------
       Martin S. Berger, Manager                 Martin S. Berger, Manager

                                       -10-<Page>

                                                                   Exhibit 10.24

                                                                  EXECUTION COPY

                                NOMINEE AGREEMENT

      THIS NOMINEE AGREEMENT ("AGREEMENT") dated as of the 3rd day of August,
2001, by and between ROBERT MARTIN COMPANY, LLC, a New York limited liability
company ("AGENT") and 5/6 SKYLINE REALTY L.L.C., a New York limited liability
company ("PRINCIPAL").

                                    RECITALS

      A. WHEREAS, pursuant to the Amended and Restated Agreement of Limited
Partnership of Madeira/RMC L.P., dated as of September 1, 1984 (as amended,
the "PARTNERSHIP AGREEMENT"), Agent, Madeira Management Company, Inc.
("MMCI") and Merlot Management Company, Inc. ("MMI" and, together with MMCI,
"MASSERY") continued the existence of a limited partnership under the laws of
the State of New York under the name of Madeira-RMC L.P. (the "PARTNERSHIP")
for the purpose, among others, of owning and developing the real property
located in the Town of Mount Pleasant, County of Westchester, and State of
New York, commonly known as 5 and 6 Skyline Drive in Mid-Westchester
Executive Park and more particularly described on EXHIBIT "A" annexed hereto
and made a part hereof (the "PROPERTY").

      B. WHEREAS, in accordance with the terms of the Partnership Agreement,
Massery has offered to purchase and acquire from Agent all of Agent's right,
title and interest in and to the Partnership (collectively, the "AGENT'S
INTEREST") and Agent has exercised its right to cause Massery to sell, assign,
transfer and convey to Agent all of Massery's right, title and interest in and
to the Partnership (collectively, the "MASSERY Interest");

      C. WHEREAS, Principal wants to acquire the Property to facilitate a
"like-kind" exchange under Section 1031 of the Internal Revenue Code of 1986, as
amended (the "CODE"), subject to the express condition that Principal is able to
acquire the Massery Interest (in the manner described below) and the Agent's
Interest in simultaneous closings;

      D. WHEREAS, Agent neither wishes nor intends to acquire the Massery
Interest for its own account but has agreed to act as Principal's agent in
acquiring the Massery Interest by serving as Principal's nominee for the sole
and limited purpose of acquiring legal title to the Massery Interest for the
sole and absolute benefit of Principal;

      E. WHEREAS, pursuant to the terms of the Partnership Agreement, Massery
has agreed to sell, assign, transfer and convey to Agent, and Agent has agreed
in accordance with this Nominee Agreement to purchase and acquire from Massery
on behalf of Principal (who is solely responsible for funding the acquisition of
the Massery Interest), title to the Massery Interest (the "MASSERY SALE"); and

      F. WHEREAS, pursuant to a Purchase and Sale Agreement between Agent and
Principal, dated August 3, 2001, Agent has agreed to sell its Agent's
Interest and any and all rights therein to Principal and Principal has agreed
to purchase such Interest, subject to the express condition that Principal is
able to acquire the Massery Interest and the Agent's Interest in

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                                                                  EXECUTION COPY

simultaneous closing.

      NOW, THEREFORE, it is hereby agreed as follows:

      1. Principal hereby appoints Agent to act as Principal's nominee for the
sole purpose of taking and holding legal title to the Massery Interest in
Agent's name for Principal's sole and absolute benefit, and Agent hereby accepts
such appointment and agrees to perform such duties for and on behalf of
Principal as are set forth in this Agreement. Agent acknowledges that Agent will
be acquiring the Massery Interest solely as nominee for and on behalf of
Principal. Principal shall have and at all times shall continue to have all
benefits, rights, privileges and liabilities accruing with respect to such
Massery Interest. Agent shall not at any time have any rights, benefits or
burdens of an owner of the Massery Interest (or any interest therein) or any
power to deal with such Massery Interest except as provided in Paragraph 2
below. Agent shall not have any obligation to provide any portion of the
purchase price and other closing costs of the Massery Sale which shall remain
the sole responsibility of Principal, and it is agreed and understood that
Principal shall timely provide and make available to Agent all funds necessary
to enable Agent to complete the closing of the Massery Sale.

      2. Agent shall have no discretionary authority to act for or on behalf of
Principal. Agent shall not do or suffer to be done any act or omission with
respect to the Property or the Massery Interest, but shall perform only such
acts as may be specifically requested by Principal in writing, including,
without limitation, the following:

              (a) Upon delivery of written instructions from Principal, Agent
shall immediately cause the Massery Interest and any interest related thereto to
be transferred and assigned to Principal or to such other person, persons or
entities as Principal may, in Principal's sole discretion, designate.

              (b) Any and all notices, statements and communications received by
Agent as owner or with respect to the Massery Interest shall be promptly given
to Principal.

              (c) If Agent shall receive any funds and/or any contracts and
documents executed in connection or accordance herewith with respect to the
Massery Interest or the Property, Agent shall disburse such funds in accordance
with the directions of Principal, either directly to Principal or to such
persons, firms and/or entities as Principal may, in Principal's sole discretion,
designate. Agent shall account to Principal for all funds so received by Agent
on behalf of Principal in such reasonable manner as Principal may from time to
time require.

              (d) If Principal desires to use the Property in a "like-kind"
exchange transaction pursuant to section 1031 of the Code, Agent shall cooperate
with and assist Principal in all reasonable respects in order to insure that the
exchange so qualifies as a "like-kind" exchange under section 1031 of the Code
and the Treasury Regulations promulgated, or to be promulgated, thereunder,
provided that such cooperation and assistance does not require Agent to take any
action which would, in Agent's opinion, involve Agent in any liability unless
Agent shall have first been indemnified to its satisfaction.

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                                                                  EXECUTION COPY

      3. Without the express written consent of Principal, Agent hereby
covenants not to disclose this Agreement or any of the terms, conditions or
other facts contained herein (other than the professionals involved in the
transaction herein contemplated or any party otherwise involved in the
respective businesses of either party hereto), or to issue any press release or
public statement related to the transaction contemplated by this Agreement,
unless required to do so by applicable law or court order, PROVIDED, HOWEVER, if
Principal issues any such press release or public statement other than one which
Principal is required to issue or make by court order or applicable law
(including all rules and regulations of the Securities Exchange Commission or
any public stock or securities exchange), then Agent shall be allowed to issue a
similar press release or public statement which shall be limited to such facts
and information as are set forth in Principal's press release or public
statement.

      4. The authority and duties of Agent hereunder shall not be delegated or
assigned by Agent except at the written direction or with the prior written
consent of Principal.

      5. Insofar as third persons dealing with Agent are concerned, Agent is
only to act as the agent and nominee of Principal and, as such, the following
provisions shall govern:

              (a) Agent, solely in its capacity as agent and nominee for
Principal (and solely with respect to third parties unless done pursuant to
Principal's written instructions or request) shall have full right, power and
authority to deal with the Massery Interest held by Agent hereunder, with the
same force and effect as though such Massery Interest were individually owned by
it; and, without limiting the generality of the foregoing; including full right
to execute and deliver any assignment or transfer relating to the Massery
Interest or any other any other instrument relating thereto.

              (b) Any and all of the foregoing instruments executed by Agent may
create obligations extending over periods of time, including periods extending
beyond the date of any possible termination of this Agreement;

              (c) No third party dealing with Agent shall be under any
obligation to inquire as to the propriety of any action or omission by Agent,
and such third party shall be conclusively protected in assuming without further
inquiry that any action taken by Agent, or any officer or employee of it acting
individually, including the execution of any instrument, is a valid and duly
authorized act of Agent as nominee and agent of Principal; and

              (d) Any member of Agent shall have full authority to execute any
and all instruments or take any and all other action which Agent is authorized
and empowered so to do by the terms of this Agreement.

      6. As between Agent on the one hand, and Principal on the other, it is
understood and agreed that Principal shall have full and exclusive power to
manage, own and deal with the Massery Interest including, without limitation,
supervising, directing and controlling any litigation, or the sale of the
Massery Interest or otherwise, assigning, conveying or disposing of the Massery
Interest. It is further understood and agreed that Agent shall act solely as the
agent

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                                                                  EXECUTION COPY

and nominee of Principal with respect to the Massery Interest and as such, when,
as, if and to the extent specifically directed by Principal shall :

              (a) Execute any instruments, including without limitation,
governmental filings, as Agent may from time to time be specifically directed by
Principal in writing;

              (b) Take any such action with respect to the Massery Interest as
may from time to time be specifically directed by Principal in writing;

              (c) Do any such other things as Agent may be specifically directed
to do by the terms of this Agreement; EXCEPT THAT Agent shall not be required to
take any action which would, in the opinion of Agent, involve Agent in any
liability unless Agent shall have first been indemnified to its satisfaction;
and

              (d) Execute only such instruments and take only such action as
shall have been authorized and directed by Principal in writing.

The provisions of this Paragraph 6 shall be applicable only as between Agent on
the one hand, and Principal on the other; but the limitations set forth in this
Paragraph 6 shall in no way limit the rights of third parties against the
Principal, or with respect to the Property for any actions taken by the Agent
pursuant to Paragraph 5 above.

      7. This Agreement shall be terminated at any time by Principal, by notice
in writing to Agent, signed and fully acknowledged, or, in all events, upon
conveyance by Agent of the Massery Interest or the Property to Principal or
Principal's designee. If the Massery Interest has not been transferred and
conveyed to Principal at the time of termination of this Agreement, Agent shall
transfer and convey title to the Massery Interest (or the Property) to Principal
at such time.

      8. This Agreement may be amended from time to time by an instrument in
writing, signed by all parties.

      9. Agent shall not be liable for any error of judgment, nor for any loss
arising out of any act or omission in good faith, but shall be responsible only
for its own willful breach of the provisions hereof. Principal shall be liable
for all debt and liabilities arising out of or occurring in connection with the
Massery Interest to the same extent and subject to the same limitations,
contractual or otherwise, as if the Principal were the record owner of the
Massery Interest

      10. In the construction hereof, whether or not so expressed, words used in
the singular or in the plural, respectively, include both the plural and
singular, words denoting males include females and words denoting persons
include individuals, firms, associations, companies, trusts and corporations,
unless a contrary intention is to be inferred from or required by the subject
matter or context.

      11. This Agreement may not be assigned by Agent or Principal; PROVIDED,
HOWEVER, that Principal may assign this Agreement to any directly or indirectly
wholly-owned subsidiary

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                                                                  EXECUTION COPY

or subsidiaries of Principal, any "qualified intermediary" (as such term is
defined in Treasury Regulation section 1.1031(k)-1(g)(iii)), any "exchange
accommodation titleholder" (as such term is defined in Revenue Procedure
2000-37, 2000-40-IRB) or any other accommodation or other party in connection
with facilitating a "like-kind" exchange under section 1031 of the Code (any
such permitted assignees, a "PERMITTED ASSIGNEE"). Any other assignment or
attempted assignment of this Agreement by Principal or Seller shall constitute a
default by such party hereunder and shall be deemed null and void and of no
force and effect.

      12. All the trusts, powers and provisions herein contained shall take
effect and be construed in accordance with the laws of the State of New York,
without regard to conflicts of laws principles.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

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                                                                  EXECUTION COPY

      WITNESS the execution hereof, under seal, in any number of counterpart
copies, each of which counterpart copy shall be deemed an original for all
purposes, as of the day first written above.

                                 ROBERT MARTIN COMPANY, LLC, a New York limited
                                 liability company

                                 By: /s/ Robert F. Weinberg
                                     --------------------------
                                 Name:    Robert F. Weinberg
                                 Title:   Manager

                                 5/6 SKYLINE REALTY L.L.C., a New York limited
                                 liability company

                                 By:   Mack-Cali Realty, L.P., a Delaware
                                       limited partnership, its sole member

                                       By:  Mack-Cali Realty Corporation,
                                            a Delaware corporation, its
                                            general partner

                                       By:  /s/  Roger W. Thomas
                                            -----------------------
                                            Roger W. Thomas,
                                            Executive Vice President

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