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                                                                   EXHIBIT 10.15


                               SECURITY AGREEMENT

         THIS SECURITY AGREEMENT (referred to herein as the "AGREEMENT"), dated
as of June 20, 2000, is made by Wilson Investors - California, LLC, a Delaware
limited liability company (the "PLEDGOR"), to and in favor of Equity Office
Properties Management Corp., a Delaware corporation ("LENDER"), in consideration
of $10.00 in hand paid by Lender to Pledgor, for other good and valuable
considerations received by Pledgor, and in order to induce Lender to make a loan
(the "LOAN") of up to $25,000,000 to Pledgor (also referred to herein as
"BORROWER") evidenced by that certain Note made by the Borrower and payable to
the order of Lender of even date herewith in the original principal amount of
$25,000,000 (the "NOTE").

         10. DEFINITIONS. All capitalized terms used herein, but not defined
shall have that meaning ascribed to them in the Note, or if not defined in the
Note, the Master Agreement. As used herein, the following terms shall have the
following meanings:

         "ACCOUNT DEBTOR" shall mean any person who is or who may become
obligated to Pledgor under, with respect to or on account of an Account.

         "ACCOUNTS" shall mean any and all right, title and interest of Pledgor
to payment for goods and services sold or leased, including any such right
evidenced by chattel paper, whether due or to become due, whether or not it has
been earned by performance, and whether now or hereafter acquired or arising in
the future.

         "ACCOUNTS RECEIVABLE" shall mean all Accounts and all right, title and
interest in any returned goods, together with all rights, titles, securities and
guarantees with respect thereto, including any rights to stoppage in transit,
replevin, reclamation and resales, and all related security interests, liens and
pledges, whether voluntary or involuntary, in each case whether now existing or
owned or hereafter arising or acquired.

         "COLLATERAL" shall mean all (a) Accounts Receivable, (b) Documents, (c)
Equipment, (d) General Intangibles, (e) Inventory, (f) cash and cash accounts,
(g) Investment Property, (h) Interests, (i) Deposit Accounts and (j) Proceeds,
together with all income and profits from all of the foregoing, all
distributions thereon, all other replacements and proceeds thereof and all
rights, benefits and privileges pertaining thereto, but notwithstanding the
foregoing, shall not include any of the following ("EXCLUDED ITEMS") (i) any and
all amounts properly distributed by WEO to Borrower (whether held by Borrower or
its members) as Permitted Holdbacks to the extent distributed prior to an Event
of Default and at a time when there exists no situation with respect to which
notice has been given by or to Borrower and which would result, with the passage
of time, in an Event of Default if such situation remains uncured; (ii) any
distributions by WEO properly made to Borrower of the Specified Project
Allocation Amount as described in Section 5.7.4 of the Master Agreement (whether
before or after an Event of Default); or (iii) any employment compensation
properly paid by WEO or its affiliates to employees of WEO or Pledgor.

         "COMMODITY ACCOUNT" shall mean an account maintained by a Commodity
Intermediary in which a Commodity Contract is carried out for a Commodity
Customer.

         "COMMODITY CONTRACT" shall mean a commodity futures contract, an option
on a commodity futures contract, a commodity option or any other contract that,
in each case, is (a) traded on or subject to the rules of a board of trade that
has been designated as a contract market for such a contract pursuant to the
federal commodities laws or (b) traded on a foreign commodity board of trade,
exchange or market, and is carried on the books of a Commodity Intermediary for
a Commodity Customer.

         "COMMODITY CUSTOMER" shall mean a person for whom a Commodity
Intermediary carries a Commodity Contract on its books.

         "COMMODITY INTERMEDIARY" shall mean (a) a person who is registered as a
futures commission merchant under the federal commodities laws or (b) a person
who in the ordinary course of its business


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provides clearance or settlement services for a board of trade that has been
designated as a contract market pursuant to federal commodities laws.

         "COPYRIGHT LICENSE" shall mean any written agreement, now or hereafter
in effect, granting any right to any third party under any Copyright now or
hereafter owned by Pledgor or which Pledgor otherwise has the right to license,
or granting any right to Pledgor under any Copyright now or hereafter owned by
any third party, and all rights of Pledgor under any such agreement.

         "COPYRIGHTS" shall mean all of the following now owned or hereafter
acquired by Pledgor: (a) all copyright rights in any work subject to the
copyright laws of the United States or any other country, whether as author,
assignee, transferee or otherwise, and (b) all registrations and applications
for registration of any such copyright in the United States or any other
country, including registrations, recordings, supplemental registrations and
pending applications for registration in the United States Copyright Office.

         "DEPOSIT ACCOUNT" shall mean a demand, time, savings, passbook, or
similar account maintained with a bank. The term does not include Investment
Property or accounts evidenced by an instrument.

         "DOCUMENTS" shall mean all instruments, files, records, ledger sheets
and documents covering or relating to any of the Collateral.

         "ENTITLEMENT HOLDER" shall mean a person identified in the records of a
Securities Intermediary as the person having a Security Entitlement against the
Securities Intermediary. If a person acquires a Security Entitlement by virtue
of Section 8-501(b)(2) or (3) of the Uniform Commercial Code, such person is the
Entitlement Holder.

         "EQUIPMENT" shall mean all equipment, furniture and furnishings, and
all tangible personal property similar to any of the foregoing, including tools,
parts and supplies of every kind and description, and all improvements,
accessions or appurtenances thereto, that are now or hereafter owned by Pledgor.
The term Equipment shall include Fixtures.

         "FINANCIAL ASSET" shall mean (a) a Security, (b) an obligation of a
person or a share, participation or other interest in a person or in property or
an enterprise of a person, which is, or is of a type, dealt with in or traded on
financial markets, or which is recognized in any area in which it is issued or
dealt in as a medium for investment or (c) any property that is held by a
Securities Intermediary for another person in a Securities Account if the
Securities Intermediary has expressly agreed with the other person that the
property is to be treated as a Financial Asset under Article 8 of the Uniform
Commercial Code. As the context requires, the term Financial Asset shall mean
either the interest itself or the means by which a person's claim to it is
evidenced, including a certificated or uncertificated Security, a certificate
representing a Security or a Security Entitlement.

         "FIXTURES" shall mean all items of Equipment, whether now owned or
hereafter acquired, of Pledgor, that become so related to particular real estate
that an interest in them arises under any real estate law applicable thereto.

         "GENERAL INTANGIBLES" shall mean all choses in action and causes of
action and all other assignable intangible personal property of Pledgor of every
kind and nature (other than Accounts Receivable) now owned or hereafter acquired
by Pledgor, including all rights and interests in partnerships, limited
partnerships, limited liability companies and other unincorporated entities,
corporate or other business records, indemnification claims, contract rights
(including rights under leases, whether entered into as lessor or lessee,
hedging agreements and other agreements), Intellectual Property, goodwill,
registrations, franchises, tax refund claims and any letter of credit,
guarantee, claim, security interest or other security held by or granted to
Pledgor to secure payment by an Account Debtor of any of the Accounts
Receivable.

         "INTELLECTUAL PROPERTY" shall mean all intellectual and similar
property of Pledgor of every kind and nature now owned or hereafter acquired by
Pledgor, including inventions, designs, Patents, COPYRIGHTS, LICENSES,
TRADEMARKS, trade secrets, confidential or proprietary technical and business
information, know-how, show-how or other data or information, software and
databases and all embodiments or fixations thereof and related documentation,
registrations and franchises, and all additions, improvements and accessions to,
and books and records describing or used in connection with, any of the
foregoing.

         "INTERESTS" shall mean Pledgor's rights to and with respect to: (a) any
property of WEO whether real, personal, tangible or intangible; (b) capital
accounts and capital contributions; (c) issues, profits, cash flow and income
(whether distributed or undistributed); (d) refinancing and sale proceeds upon
termination and dissolution of WEO or otherwise; (e) any and all property of WEO
distributed to Pledgor at any time;


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(f) any amounts owed or paid to Pledgor on account of any indebtedness of WEO to
Pledgor (whether or not evidenced by instruments of indebtedness); (g) all
compensation due, owing or paid to Pledgor by WEO; (h) any and all property
received by Pledgor on account of Pledgor being a member in or creditor of WEO;
(i) any and all amounts (including cash, notes and any security therefor)
received by Pledgor in connection with a sale by Pledgor of its interest in WEO
(provided, however, that Lender shall not be deemed to have approved any such
sale); (j) any refinancing or sale proceeds upon the refinancing, sale,
conveyance or other disposition of the Property; (k) any products, proceeds or
avails of any of the foregoing; and (l) any voting rights and other rights to
control or influence WEO's decisions (provided, however, that, prior to an Event
of Default, Pledgor shall have the unrestricted right (without any consent from
Lender) to exercise such voting rights and rights to control or influence WEO's
decisions); (m) any B Unit in WEO distributed or otherwise transferred to
Pledgor by Lender; and (n) all replacements, additions, accessions,
substitutions, proceeds and products relating thereto or therefrom, and all
documents, ledger sheets and files of Pledgor relating thereto.

         "INVENTORY" shall mean all goods of Pledgor, whether now owned or
hereafter acquired, held for sale or lease, or furnished or to be furnished by
Pledgor under contracts of service, or consumed in Pledgor's business, including
raw materials, intermediates, work in process, packaging materials, finished
goods, semi-finished inventory, scrap inventory, manufacturing supplies and
spare parts, and all such goods that have been returned to or repossessed by or
on behalf of Pledgor.

         "INVESTMENT PROPERTY" shall mean all Securities (whether certificated
or uncertificated), Security Entitlements, Securities Accounts, Commodity
Contracts and Commodity Accounts of Pledgor, whether now owned or hereafter
acquired by Pledgor.

         "LICENSE" shall mean any Patent License, Trademark License, Copyright
License or other license or sublicense to which Pledgor is a party (other than
those license agreements in existence on the date hereof and those license
agreements entered into after the date hereof, which by their terms prohibit
assignment or a grant of a security interest by Pledgor as licensee thereunder).

         "PATENT LICENSE" shall mean any written agreement, now or hereafter in
effect, granting to any third party any right to make, use or sell any invention
on which a Patent, now or hereafter owned by Pledgor or which Pledgor otherwise
has the right to license, is in existence, or granting to Pledgor any right to
make, use or sell any invention on which a Patent, now or hereafter owned by any
third party, is in existence, and all rights of Pledgor under any such
agreement.

         "PATENTS" shall mean all of the following now owned or hereafter
acquired by Pledgor: (a) all letters patent of the United States or any other
country, all registrations and recordings thereof, and all applications for
letters patent of the United States or any other country, including
registrations, recordings and pending applications in the United States Patent
and Trademark Office or any similar offices in any other country, and (b) all
reissues, continuations, divisions, continuations-in-part, renewals or
extensions thereof, and the inventions disclosed or claimed therein, including
the right to make, use and/or sell the inventions disclosed or claimed therein.

         "PROCEEDS" shall mean any consideration received from the sale,
exchange, license, lease or other disposition of any asset or property that
constitutes Collateral, any value received as a consequence of the possession of
any Collateral and any payment received from any insurer or other person or
entity as a result of the destruction, loss, theft, damage or other involuntary
conversion of whatever nature of any asset or property which constitutes
Collateral, and shall include (a) all cash and negotiable instruments received
by or held on behalf of the Administrative Agent, (b) any claim of Pledgor
against any third party for (and the right to sue and recover for and the rights
to damages or profits due or accrued arising out of or in connection with) (i)
past, present or future infringement of any Patent now or hereafter owned by
Pledgor, or licensed under a Patent License, (ii) past, present or future
infringement or dilution of any Trademark now or hereafter owned by Pledgor or
licensed under a Trademark License or injury to the goodwill associated with or
symbolized by any Trademark now or hereafter owned by Pledgor, (iii) past,
present or future breach of any License and (iv) past, present or future
infringement of any Copyright now or hereafter owned by Pledgor or licensed
under a Copyright License and (c) any and all other amounts from time to time
paid or payable under or in connection with any of the Collateral.

         "SECURED OBLIGATIONS" shall mean all of Pledgor's obligations,
including without limitation payment of amounts due, under the Note and the
other Loan Documents (as defined in the Note).

         "SECURITIES" shall mean any obligations of an issuer or any shares,
participations or other interests in an issuer or in property or an enterprise
of an issuer which (a) are represented by a certificate representing a security
in bearer or registered form, or the transfer of which may be registered upon
books


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maintained for that purpose by or on behalf of the issuer, (b) are one of a
class or series or by its terms is divisible into a class or series of shares,
participations, interests or obligations and (c)(i) are, or are of a type, dealt
with or trade on securities exchanges or securities markets or (ii) are a medium
for investment and by their terms expressly provide that they are a security
governed by Article 8 of the Uniform Commercial Code.

         "SECURITIES ACCOUNT" shall mean an account to which a Financial Asset
is or may be credited in accordance with an agreement under which the person
maintaining the account undertakes to treat the person for whom the account is
maintained as entitled to exercise rights that comprise the Financial Asset.

         "SECURITY ENTITLEMENTS" shall mean the rights and property interests of
an Entitlement Holder with respect to a Financial Asset.

         "SECURITIES INTERMEDIARY" shall mean (a) a clearing corporation or (b)
a person, including a bank or broker, that in the ordinary course of its
business maintains securities accounts for others and is acting in that
capacity.

         "TRADEMARK LICENSE" shall mean any written agreement, now or hereafter
in effect, granting to any third party any right to use any Trademark now or
hereafter owned by Pledgor or which Pledgor otherwise has the right to license,
or granting to Pledgor any right to use any Trademark now or hereafter owned by
any third party, and all rights of Pledgor under any such agreement.

         "TRADEMARKS" shall mean all of the following now owned or hereafter
acquired by Pledgor: (a) all trademarks, service marks, trade names, corporate
names, company names, business names, fictitious business names, trade styles,
trade dress, logos, other source or business identifiers, designs and general
intangibles of like nature, now existing or hereafter adopted or acquired, all
registrations and recordings thereof, and all registration and recording
applications filed in connection therewith, including registrations and
registration applications in the United States Patent and Trademark Office, any
State of the United States or any similar offices in any other country or any
political subdivision thereof, and all extensions or renewals thereof, (b) all
goodwill associated therewith or symbolized thereby and (c) all other assets,
rights and interests that uniquely reflect or embody such goodwill.

         11. PLEDGE.

                  11.1 GRANT OF SECURITY INTEREST. To secure the Secured
Obligations and other amounts and obligations due hereunder, Pledgor hereby
pledges to Lender, and grants to Lender a security interest in, all of the
Collateral.

                  11.2 MATERIAL INDUCEMENT. Pledgor hereby acknowledges that, in
addition to the consideration recited above, Lender has given sufficient
consideration for this Agreement and the assignment described herein by loaning
funds under the Note. Pledgor further acknowledges that Lender is doing so in
reliance on each of the terms of this Agreement and that the foregoing
assignment of the Collateral is a material inducement to Lender to make such
loan.

                  11.3 NO ASSUMPTION OF LIABILITY. By its acceptance hereof,
Lender shall not be deemed to have assumed or become liable for any other
obligations or liabilities of Pledgor under the Master Agreement, whether
provided for by the terms thereof or arising by operation of law or otherwise.
Pledgor hereby acknowledges and agrees that Pledgor is and remains liable
thereunder to the same extent as though this Agreement had not been executed and
delivered.

                  11.4 NO DISTRIBUTIONS. Pledgor hereby acknowledges that,
except for the Excluded Items, Pledgor shall not receive any distributions on
account of the Interests, nor shall Pledgor make any distributions or other
payments. In addition, with respect to the Excluded Items, upon the occurrence
of an event or existence of a situation with respect to which notice has been
given by or to Borrower and which would result,


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with the passage of time, in an Event of Default, the Borrower shall have no
right to receive any distributions of the Permitted Holdbacks until such event
or situation has been cured, provided that any and all other Excluded Items may
be distributed to Borrower notwithstanding that such an event or situation has
occurred and notwithstanding any Event of Default.

         12. DEFAULTS AND REMEDIES.

                  12.1 DEFAULTS. The occurrence of any one or more of the
following events or conditions with respect to Pledgor shall constitute an event
of default ("EVENT OF DEFAULT") under this Agreement:

                           12.1.1 Pledgor fails to keep or perform any of its
agreements, undertakings, obligations, covenants or conditions under this
Agreement and such failure continues for a period of 30 days after notice
thereof from Lender to Pledgor provided, that if such failure cannot, because of
its nature, be cured within said 30 day period, then, if Pledgor commences
curing such failure within said 30 day period and diligently continues to
attempt to cure such failure, Pledgor shall have up to an additional 90 day
period to cure such failure.

                           12.1.2 Any representation, warranty or certification
made in this Agreement by Pledgor or otherwise made in writing in connection
with or as contemplated by this Agreement or any of the other Loan Documents by
Pledgor or Borrower shall be or become materially incorrect or false.

                           12.1.3 An "Event of Default" shall occur under any of
the Loan Documents.

                           12.1.4 The filing of a petition by Pledgor for relief
under the Bankruptcy Code, or under any other present or future state or federal
law regarding bankruptcy, reorganization or other debtor relief law; the filing
of any pleading or an answer by Pledgor in any involuntary proceeding under the
Bankruptcy Code or other debtor relief law which admits the jurisdiction of the
court or the petition's material allegations regarding Pledgor's insolvency; a
general assignment by Pledgor for the benefit of creditors; or Pledgor applying
for, or the appointment of, a receiver, trustee, custodian or liquidator of
Pledgor or any of its property.

                           12.1.5 The failure of Pledgor to effect a full
dismissal of any involuntary petition under the Bankruptcy Code or any other
debtor relief law that is filed against Pledgor or in any way restrains or
limits Pledgor or Lender regarding the Loan, the Property, prior to the earlier
of the entry of any court order granting relief sought in such involuntary
petition, or 120 days after the date of filing of such involuntary petition.

                           12.1.6 Any receiver, trustee or custodian is
appointed to take possession of all or any substantial portion of the assets of
Pledgor.


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                  12.2 REMEDIES. Upon the occurrence of an Event of Default
hereunder, Lender may, at its option, without notice to or demand upon Pledgor
or WEO, do any one or more of the following:

                           12.2.1 Declare the Loan and all other indebtedness of
Pledgor to Lender to be immediately due and payable, whereupon all unpaid
principal and interest on said advances and other indebtedness shall become and
be immediately due and payable.

                           12.2.2 Exercise any or all of the rights and remedies
provided for by the Code, specifically including, without limitation, the right
to recover the reasonable attorneys' fees and other expenses incurred by Lender
in the enforcement of this Agreement.

                           12.2.3 Notify WEO that Lender has the right to
receive any distributions from the Collateral; Pledgor hereby authorizes and
directs WEO, after the occurrence and during the pendency of an Event of
Default, to make all payments and distributions, with respect to the Collateral,
to which Pledgor would otherwise be entitled, directly to Lender to be applied
to the Loan and agrees to promptly deliver to Lender any distributions and
payments with respect to the Collateral that it nevertheless receives.

                           12.2.4 Retain the Interests (except for the Excluded
Items) in satisfaction of the obligations secured hereby, with notice of such
retention sent to either Pledgor or WEO, if required by law, or transfer the
Interests or any portion thereof (except for the Excluded Items) into the name
of its nominee.

                           12.2.5 Proceed by an action or actions at law or in
equity with respect to the obligations secured hereby or to foreclose this
Agreement and sell the Collateral, or any portion thereof, pursuant to a
judgment or decree of a court or courts of competent jurisdiction; at the option
of Lender, Pledgor shall cause the Collateral to be marketed and sold in
accordance with the requirements of Lender.

                           12.2.6 Enforce one or more remedies hereunder,
successively or concurrently, and such action shall not operate to estop or
prevent Lender from pursuing any other or further remedy which it may have, and
any repossession or retaking or sale of the Collateral or any portion thereof
pursuant to the terms hereof shall not operate to release Pledgor of its
obligations hereunder until full and final payment of any deficiency has been
made in cash. Pledgor shall reimburse Lender from the Collateral for, or Lender
may apply any proceeds of the Collateral to, the costs and expenses (including
attorneys' fees, transfer taxes and any other charges) incurred by Lender in
connection with any sale, disposition or retention of the Collateral hereunder.

                  12.3 NO MARSHALLING. Lender shall not be required to marshall
the Collateral or any other security for the obligations secured hereby or to
resort to the Collateral or any other security for the obligations secured
hereby in any particular order and all of Lender's rights under the various
instruments relating to the collateral shall be cumulative.


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                  12.4 WAIVER. Pledgor, to the maximum extent permitted by law,
hereby waives every defense (now, theretofore or hereafter arising) of estoppel,
laches, extension or moratorium applicable to any obligations or liabilities
covered by this Agreement or of Pledgor under this Agreement and any claim that
the release, substitution or addition of any portion of the Collateral,
endorsers or guarantors affects the liability of Pledgor hereunder. Pledgor also
expressly waives extension of the obligations of this Agreement arising by any
reason whatsoever, including, without limitation, by reason of the institution
of proceedings by or against Pledgor or WEO under or pursuant to the Federal
Bankruptcy Code, or any amendment thereto, or any similar state or federal laws
relating to the relief of debtors.

                  12.5 JUDICIAL PROCESS. In the event Lender recovers possession
of all or any part of the Collateral pursuant to a writ of possession or other
judicial process, whether prejudgment or otherwise, Lender may thereafter
retain, sell or otherwise dispose of the Collateral in accordance with this
Agreement or the Code, and following such retention, sale or other disposition,
Lender may voluntarily dismiss without prejudice the judicial action in which
such writ of possession or other judicial process was issued. Pledgor hereby
consents to the voluntary dismissal by Lender of such judicial action, and
Pledgor further consents to the exoneration of any bond which Lender filed in
such action.

                  12.6 SALE. Lender may sell the Collateral, or any part
thereof, at any public or private sale or at any broker's board or on any
securities exchange, for cash, upon credit or for future delivery, as Lender
shall deem appropriate. Lender shall be authorized at any such sale, if it deems
it advisable to do so, to restrict the prospective bidders or purchasers to
persons who will provide assurances satisfactory to Lender that the Collateral
may be offered and sold without registration under the Securities Act of 1933,
as amended (the "SECURITIES ACT") or any statute then in effect corresponding to
the Securities Act, and upon consummation of any such sale, Lender shall have
the right to assign, transfer and deliver to the purchaser or purchasers thereof
the Collateral so sold. Each such purchaser at any such sale shall hold the
property sold absolutely free from any claim or right on the part of either
Pledgor, and Pledgor hereby waives, to the extent permitted by law, all rights
of redemption and reinstatement, stay and/or appraisal which Pledgor now has or
may at any time in the future have under any rule of law or statute now existing
or hereafter enacted. In any sale of the Collateral, the Interests shall be sold
subject to the Excluded Items in favor of Pledgor. Lender shall give Pledgor
written notice, at least 10 days in advance of Lender's intention to make any
such public or private sale. Such notice, in case of public sale, shall state
the time and place fixed for such sale, and in the case of sale at a broker's
board or on a securities exchange, shall state the board or exchange at which
such sale is to be made and the day on which the Collateral, or portion thereof,
will first be offered for sale at such board or exchange. Any such public sale
shall be held at such time or times within ordinary business hours and at such
place or places as Lender may fix in the notice of such sale. At any private or
public or other sale, the Collateral, or portion thereof, to be sold may be sold
in one lot as an entirety or in separate parts, as Lender may in its sole and
absolute discretion determine and Lender may bid (which bid may be, in whole or
in part, in the form of cancellation of indebtedness) for and purchase for its
account the whole or any part of the


<PAGE>   8


Collateral at any public sale or sale at a broker's board or on a security
exchange. Lender shall not be obligated to sell any Collateral if it shall
determine not to do so, regardless of the fact that notice of sale of Collateral
may have been given. Lender may, without notice or publication, adjourn any sale
or cause the same to be adjourned from time to time by announcement at the time
and place fixed for sale, and such sale may, without further notice, be made at
the time and place to which the same was so adjourned. In case sale of all or
any part of the Collateral is made on credit or for future delivery, the
Collateral so sold may be retained by Lender until the sale price is paid by the
purchaser or purchasers thereof, but Lender shall not incur any liability in
case any such purchaser or purchasers shall fail to take up and pay for the
Collateral so sold and, in case of any such failure, such Collateral may be sold
again upon like notice. The parties hereto agree that the method, manner and
terms of sale or disposition of the Collateral authorized by this subsection are
commercially reasonable. As an alternative to exercising the powers herein
conferred upon it, Lender may, without limitation, proceed by a suit or suits at
law or in equity to foreclose this Agreement and to sell the Collateral, or any
portion thereof, pursuant to a judgment or decree or a court or courts of
competent jurisdiction.

                  12.7 PROTECTION OF COLLATERAL. At any time after the
occurrence and during the pendency of an Event of Default, Lender shall have the
right to make any payments and do any other acts Lender may deem necessary to
protect its security interest in the Collateral, including, without limitation,
the rights to pay, purchase, contest or compromise any encumbrance, charge or
lien which in the judgment of Lender appears to be prior to or superior to the
security interest granted hereunder, and appear in and defend any action or
proceeding purporting to affect its security interest in and/or the value of the
Collateral, and in exercising any such powers or authority, the right to pay all
expenses incurred in connection therewith, including attorneys' fees. Pledgor
hereby agrees to reimburse Lender for all reasonable payments made and expenses
incurred, which amounts shall be secured under this Agreement, and agrees it
shall be bound by any payment made or act taken by Lender hereunder. Lender
shall have no obligation to make any of the foregoing payments or perform any of
the foregoing acts.

         13. REPRESENTATIONS, WARRANTIES AND COVENANTS OF PLEDGOR. Pledgor
represents, warrants and agrees that:

                  13.1 TITLE. It is the legal, record and beneficial owner of,
and has good and marketable title to, the Collateral, subject to no lien, claim,
charge, restriction, pledge, security interest or other encumbrance
(collectively, "LIEN") except the pledge and security interest created by this
Agreement or under the Loan Documents or Sections 5.5 of 10.2.3 of the Master
Agreement (if any were created under such sections).

                  13.2 VALID FIRST PRIORITY SECURITY INTEREST. The pledge,
assignment and delivery of the Collateral pursuant to this Agreement and the
filing of the appropriate UCC-1 financing statement by Lender in Delaware and
California creates a valid perfected first priority security interest in the
Collateral, and the proceeds thereof, subject to no Lien or to any agreement
purporting to grant to any third party a security interest in the property or
assets of Pledgor which would include the Collateral.


<PAGE>   9


                  13.3 PLEDGOR'S LOCATION. As of the date hereof and the date of
every Advance, Pledgor's chief office and place of business is located at
Borrower's address set forth in the Note, and its records concerning the
Collateral are kept at said office. Pledgor will not change its chief office nor
its chief place of business nor the place where it maintains its records
concerning the Collateral from the location specified above without giving 30
days' prior written notice thereof to Lender, provided, however, that, as and to
the extent provided in the Loan Agreement, written notice to EOP Investor,
L.L.C. shall be deemed to be written notice to Lender.

                  13.4 CONSENTS. As of the date hereof and the date of every
Advance, no consents are necessary in connection with the execution and delivery
by Pledgor of this Agreement and all other agreements, instruments and documents
referred to herein or contemplated hereby and executed by Pledgor. Pursuant to
the Loan Agreement, EOP Investor, L.L.C. is confirming its consent to the Loan
Documents.

                  13.5 TRANSFERS. Without the prior written consent of Lender,
Pledgor agrees that it will not sell, assign, transfer, exchange, or otherwise
dispose of, or grant any option with respect to, the Collateral, nor will it
create, incur or permit to exist any Lien with respect to any of the Collateral,
or any interest therein, or any proceeds thereof, except for the security
interest and pledge provided for by this Agreement or otherwise under the Loan
Documents or Sections 5.5 or 10.2.3 of the Master Agreement (if any were created
under such sections).

                  13.6 DELIVERY OF CERTAIN COLLATERAL. Pledgor covenants and
agrees that if at any time any of the Collateral not now evidenced by any
promissory note, draft, bond, acceptance, certificate or other instrument shall
become evidenced by a promissory note, draft, bond, acceptance, certificate or
other instrument, Pledgor will immediately deliver such promissory note, draft,
bond, acceptance, certificate or other instrument to Lender, properly endorsed
in blank, as Collateral hereunder.

                  13.7 DEFEND TITLE. Pledgor covenants and agrees that it will
defend Lender's right, title and security interest in and to the Collateral and
the proceeds thereof against the claims and demands of all persons and entities
whomsoever, and Pledgor covenants and agrees that it will have like title to and
right to pledge or grant a security interest in any other property at any time
hereafter pledged or granted to Lender as Collateral hereunder and will likewise
defend Lender's right thereto and security interest therein.

                  13.8 NO OTHER FINANCING STATEMENT. No financing statement
covering the Collateral, or any part thereof is on file in any public office,
and Pledgor shall, at the request of Lender, join with Lender in executing a
financing statement pursuant to the Uniform Commercial Code, as adopted in
Illinois, (the "CODE"), and pay the fee for filing same in all public offices
where filing may reasonably be deemed necessary by Lender.

                  13.9 DISCHARGE OF LIENS. Pledgor shall pay any indebtedness
which may be secured by a lien or charge upon the Collateral and otherwise keep
the Collateral


<PAGE>   10


free of unpaid charges; upon request, Pledgor shall deliver to Lender reasonably
satisfactory evidence of any such payment. Upon the occurrence of an Event of
Default (defined below) relating to any such payment, Lender may, but is not
obligated to, make any payment required of Pledgor in the protection of the
Collateral and purchase, discharge, compromise or settle any lien or other title
claim, or cause same to be bonded or insured over in a manner satisfactory to
Lender, or redeem from any sale or foreclosure affecting the Collateral, or
contest any tax or assessment. All money advanced by Lender for any of the
purposes stated in this Agreement or for the protection of the Collateral or of
the lien of Lender therein (whether or not described in this Agreement), or in
the enforcement (judicially or otherwise) of its rights hereunder, and all
reasonable expenses paid or incurred in connection therewith, including, without
limitation, attorneys' fees and expenses, shall be additional indebtedness
secured by the security interest created by this Agreement and become
immediately due and payable without notice and with interest thereon at the rate
applicable under the Note.

                  13.10 MASTER AGREEMENT. As of the date hereof, true and
correct copies of the Master Agreement and the Certificate of Formation of WEO
(the "CERTIFICATE") are attached hereto as EXHIBIT A and the foregoing are in
full force and effect. Pledgor shall not agree to any amendment or modification
of the Master Agreement, and shall not permit the liquidation, winding up or
termination of WEO, without the prior written consent of Lender, provided,
however, that, as and to the extent provided in the Loan Agreement, the consent
of EOP Investor, L.L.C. shall be deemed to be a consent binding upon Lender.

                  13.11 BORROWER'S RECORDS. Pledgor shall cause WEO to keep and
maintain books and records of accounts in which full, true and correct entries
shall be made of all dealings and transactions relating to WEO and the
Interests, which books and records of account shall at all normal business hours
following reasonable notice be open to the inspection of Lender and its
accountants and other duly authorized representatives of Lender.

                  13.12 NO CONFLICT OR BREACH. As of the date hereof and the
date of every Advance, except for matters disclosed to Lender prior to such
dates and which taken as a whole do not have a material adverse effect upon
Borrower or its ability to pay any amount owed hereunder (as determined by
Lender in its sole and absolute discretion), neither the execution and delivery
of this Agreement by Pledgor nor the fulfillment of the terms and provisions
hereof (including any exercise of Lender's remedies hereunder) require the
consent of any third party (including, without limitation, any lender), nor will
same result in a breach of any of the terms or provisions of, or constitute a
default under, or constitute an event which, with notice or lapse of time, or
both, will result in a breach of or constitute a default under, (a) the Master
Agreement or (b) any other agreement, indenture, mortgage, deed of trust,
equipment lease, instrument or other document to which either Pledgor or WEO is
a party which (i) would have a material adverse effect on Pledgor or WEO, (ii)
conflict with any law, order, rule or regulation applicable to either Pledgor or
WEO of any court or any federal or state government, regulatory body or
administrative agency, or any other governmental body having jurisdiction over
either Pledgor or WEO or its properties, or (iii) conflict with the Master
Agreement, provided,


<PAGE>   11


however, that the foregoing representation is made in reliance upon the consent
of EOP Investor, L.L.C. to the Loan Documents set forth in the Master Agreement.

                  13.13 ASSURANCES REGARDING PERFECTION. Pledgor will cause WEO
to keep a copy of this Agreement with the records of WEO and to denote wherever
appropriate elsewhere in such records that the Collateral has been assigned to
Lender as collateral hereunder. In addition, Pledgor will, promptly upon request
by Lender, procure or execute and deliver any document, give any notices,
execute and file any financing statements, mortgages or other documents, all in
form and substance reasonably satisfactory to Lender, mark any chattel paper,
deliver any chattel paper or instruments to Lender and take any other actions
which are necessary or, in the reasonable judgment of Lender, desirable to
perfect or continue the perfection and first priority of Lender's security
interest in the Collateral, to protect the Collateral against the rights, claims
or interests of third persons or to effect the purposes of this Security
Agreement, including, without limitation, causing the Collateral to be
certificated and the delivery of the certificates to Lender, and will pay all
reasonable costs incurred in connection therewith.

                  13.14 NOTICE OF STATUS. Pledgor will, upon Lender's reasonable
request, deliver to Lender records and schedules which show the status and
condition of the Collateral and of Lender's security interest therein. Pledgor
will promptly notify Lender in writing of any event, or change of law,
regulation, business practice or business condition which materially adversely
affects the value of the Collateral.

                  13.15 COMPLIANCE. Pledgor will comply with all laws, statutes
and regulations pertaining to the use or ownership of the Collateral.

                  13.16 ERISA. Pledgor covenants to Lender that, for so long as
this Agreement shall be continuing, Pledgor will not be an "employee benefits
plan" (within the meaning of Section 3(3) of ERISA) to which ERISA applies and
Pledgor's assets will not constitute assets of any such plan.

         14. REMEDIES CUMULATIVE, ETC. Each right, power and remedy of Lender
provided in this Agreement or now or hereafter existing at law or in equity or
by statute or otherwise shall be cumulative and concurrent and shall be in
addition to every other right, power or remedy provided for in this Agreement or
now or hereafter existing at law or in equity or by statute or otherwise. The
exercise or partial exercise by Lender of any one or more of such rights, powers
or remedies shall not preclude the simultaneous or later exercise by Lender of
all such other rights, powers or remedies, and no failure or delay on the part
of Lender to exercise any such right, power or remedy shall operate as a waiver
thereof.

         15. OBLIGATIONS ABSOLUTE, ETC. The obligations of Pledgor under this
Agreement shall be absolute and unconditional and shall remain in full force and
effect without regard to, and shall not be released, discharged or in any way
impaired by any circumstance whatsoever, including without limitation: (a) any
amendment or modification of the Note or any document or instrument executed in
connection therewith or provided for herein or therein, or any assignment,
transfer or other disposition of any


<PAGE>   12


thereof; (b) any waiver, consent, extension, indulgence or other action or
inaction under or in respect of any such document or instrument or any exercise
or non-exercise of any right, remedy, power or privilege under or in respect of
any such document or instrument or this Agreement; (c) any bankruptcy,
insolvency, reorganization, arrangement, readjustment, composition, liquidation
or similar proceeding with respect to Pledgor any guarantor or any of their
respective properties or creditors; or (d) any limitation on Pledgor's or any
guarantor's liability or obligations under any such instrument or any invalidity
or unenforceability, in whole or in part of any such document or instrument or
any term thereof; whether or not Pledgor shall have notice or knowledge of the
foregoing.

         16. TERMINATION AND RELEASE. This Agreement shall terminate 367 days
after all amounts payable pursuant to the Note have been paid. At the time of
such termination, Lender, at the request and expense of Pledgor, will execute
and deliver to Pledgor a proper instrument or instruments acknowledging the
satisfaction and termination of this Agreement, and will duly assign, transfer
and deliver to Pledgor such of the Collateral as has not yet theretofore been
sold or otherwise applied or released pursuant to this Agreement, together with
any unapplied monies at the time held by or Lender hereunder.

         17. FURTHER ASSURANCES. Pledgor, at its expense, will duly execute,
acknowledge and deliver all such instruments and take all such action as Lender
from time to time may request in order further to effectuate the purposes of
this Agreement and to carry out the terms hereof. Pledgor, at his expense, will
at all times cause this Agreement (or a proper notice or statement in respect
hereof) to be duly recorded, published, filed and lodged and rerecorded,
republished, refiled and relodged in such manner and in such places, if any, and
will pay or cause to be paid all fees and charges in connection therewith, if
any, and will comply with all such statutes and regulations, if any, as may be
required by law in order to establish, perfect, preserve and protect the rights
and security interests of Lender hereunder.

         18. MISCELLANEOUS.

                  18.1 NOTICES. All communications provided for or related
hereto shall be given in accordance with Section 13.7 of the Master Agreement.

                  18.2 AMENDMENTS AND WAIVERS. Any term of this Agreement may be
amended and the observance of any term hereof may be waived (either generally or
in a particular instance and either retroactively or prospectively) only with
the written consent of Pledgor and Lender. Any amendment or waiver effected in
accordance with this section shall be binding upon each holder of the Note at
the time outstanding, each future holder of the Note and Pledgor.

                  18.3 SUCCESSORS AND ASSIGNS. This Agreement shall be binding
upon and inure to the benefit of and be enforceable by the respective successors
and assigns of the parties hereto, whether so expressed or not, and, in
particular, shall inure to the benefit of and be enforceable by Lender. Lender
may assign its rights hereunder to any Affiliate.


<PAGE>   13


                  18.4 ENTIRE AGREEMENT. Together with the Loan Documents, this
Agreement embodies the entire agreement and understanding between Lender and
Pledgor and supersedes all prior agreements and understandings between them
relating to the subject matter hereof.

                  18.5 CHOICE OF LAW. This Agreement shall be construed and
enforced in accordance with and governed by the law of the State of Illinois.

                  18.6 ENFORCEMENT COSTS. Pledgor shall reimburse Lender upon
demand for all its costs of collection under this Agreement and costs of
realization on the Pledged Security (including, without limitation, attorneys'
fees and expenses).

                  18.7 INTERPRETATION. The headings in this Agreement are for
purposes of reference only and shall not limit or otherwise affect the meaning
hereof.

                  18.8 COUNTERPARTS. This Agreement may be executed in any
number of counterparts, each of which shall be an original, but all of which
together shall constitute one instrument.


<PAGE>   14


         IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed and delivered by their respective officers thereunto duly authorized as
of the date first above written.

                                      PLEDGOR:

                                      WILSON INVESTORS - CALIFORNIA, LLC,
                                      a Delaware limited liability company

                                      By:   /s/ TOM SULLIVAN
                                            ------------------------------------
                                      Name:  Tom Sullivan
                                            ------------------------------------
                                      Its:   Manager
                                            ------------------------------------

                                      LENDER:

                                      EQUITY OFFICE PROPERTIES MANAGEMENT CORP.,
                                      a Delaware corporation

                                      By:    /s/ STANLEY M. STEVENS
                                            ------------------------------------
                                      Name:  Stanley M. Stevens
                                            ------------------------------------
                                      Its:   Vice President
                                            ------------------------------------