
<PAGE>
 
                                                                   EXHIBIT 10.45

                             MODIFICATION AGREEMENT


          THIS AGREEMENT made as of the 30th day of May, 1990, by and between
KENVIC ASSOCIATES ("Mortgagor"), a New York general partnership having its
principal office and place of business at 875 Third Avenue, New York, New York
10022 and JOHN HANCOCK MUTUAL LIFE INSURANCE COMPANY ("Mortgagee"), a
Massachusetts corporation having its principal office at John Hancock Place,
Post Office Box 111, Boston, Massachusetts 02117, Attention: City Mortgage and
                                                  ---------
Real Estate Department.



                        W I T N E S S E T H    T H A T:
                        - - - - - - - - - -    - - - -  


          WHEREAS, Mortgagor is on the date of delivery hereof the owner of fee
title to the premises described in Schedule A hereto, including the
Declarations, Declaration of Zoning Lot Restrictions, and the easements more
particularly described in such Schedule A (collectively, the "LAND");

          WHEREAS, Mortgagor is on the date of delivery hereof the owner of the
fee interest in all buildings, structures, and other improvements now or
hereafter located on the Land; and

          WHEREAS, Mortgagee is on the date of delivery hereof the owner and
holder of those certain mortgages more particularly described in the
Consolidation, Extension and Modification Agreement (the "Consolidation
Agreement"), dated as of May 11, 1988, between Mortgagor and Mortgagee and
recorded in the Office of the Register of the City of New York (the "Register's
Office") on May 18, 1988 in Reel 1403 at page 1793, which mortgages were
consolidated pursuant to the Consolidation Agreement so as to constitute a
single first lien on the property described therein in the amount of
$180,000,000; and

          WHEREAS, Mortgagor and Mortgagee desire to modify the Consolidation
Agreement in the manner herein set forth;
<PAGE>
 
          NOW, THEREFORE, in consideration of the premises and the mutual
covenants herein contained, Mortgagor agrees with Mortgagee as follows:

          1.   Modification of Section 2.10.2   The first sentence of Section
               ------------------------------                                
2.10.2 of the Consolidation Agreement is deleted in its entirety and the
following is substituted in lieu thereof:

          Promptly upon the expiration or earlier termination of the lease noted
     in Memorandum of Lease from Rosa A. Cordes and Henry G. Barteld to 873
     Third Avenue Corp., dated May 6, 1959, recorded in the Register's Office in
     Liber 5076 at page 302, in respect of the land and buildings (the "Existing
     Buildings") located on the parcel of land more particularly described in
     Schedule D hereto (the "Corner Parcel"), Mortgagor will at its own expense
     commence and promptly and diligently prosecute to completion, demolition of
     the Existing Buildings and will thereafter construct, develop and complete
     on such Corner Parcel, a new structure (the "Building Addition"), all as
     provided in and in accordance with the terms of the Declaration, dated
     January 7, 1981, made by Kenvic Associates, Arnold J. Rabinor, Marvin B.
     Tepper and Kenneth Gladstone, recorded in the Register's Office in Reel 556
     at page 541 and in Reel 556 at page 1281, as modified by Modification of
     Declaration, dated as of June 14, 1982, between Kenvic Associates and 875
     Third Associates, recorded in the Register's Office in Reel 653 at page
     1315, as further modified by Second Modification to Declaration, dated as
     of December 7, 1983, between Kenvic Associates and 875 Third Associates,
     recorded in the Register's Office in Reel 745 at page 533 and as further
     modified by Third Modification to Declaration, dated as of May 30, 1990, by
     Kenvic Associates, to be recorded in the Register's Office immediately
     prior to the recordation of the Modification Agreement (the "Modification
     Agreement"), dated as of May 30, 1990, between Mortgagor and Mortgagee, as
     such Declaration may be further amended from time to time subsequent to the
     date of the Modification Agreement with the consent of the City of New York
     and Mortgagee, which consent will not be unreasonably withheld by Mortgagee
     (said Declaration, as amended and hereinafter amended from time to time

                                       2
<PAGE>
 
     in accordance with the terms hereof, is herein referred to as the "Special
     Permit Declaration").

          2.   Modification of Section 2.18.  Section 2.18 of the Consolidation
               ----------------------------                                    
Agreement is hereby amended by inserting, immediately after the phrase "as party
to the Declaration of Zoning Lot Restrictions, dated January 7, 1981, made by
Mortgagor, Arnold J. Rabinor, Marvin B. Tepper and Kenneth Gladstone, recorded
in the Register's Office in Reel 552 at page 737" and before the phrase "(the
"Zoning Declaration")", the following:

     ", as such Declaration of Zoning Lot Restrictions may be modified and
     amended from time to time subsequent to the date hereof with the consent of
     Mortgagee and, if required, the City of New York"

               Section 2.18 of the Consolidation Agreement is further amended by
inserting, immediately after the phrase "as party to the Agreement, dated as of
December 6, 1982, entered into among Mortgagor, 875 Third Associates, the New
York City Transit Authority and The Chase Manhattan Bank, N.A." and before the
phrase "("the Transit Authority Agreement")", the following:

     ", as such Agreement may be modified and amended from time to time
     subsequent to the date hereof with the consent of the New York City Transit
     Authority and MORTGAGEE"

          Section 2.18 of the Consolidation Agreement is further amended by
inserting, immediately after the phrase "as holder of the special permit granted
by the New York City Board of Estimate" and before the phrase "(the "Special
Permit")", the following:

     ", as such special permit may be modified and amended from time to time
     subsequent to the date hereof with the consent of the City of New York"

          Section 2.18 of the Consolidation Agreement is further amended by
inserting, immediately after the phrase "as declarant under the Declaration of
Easement, dated as of July 17, 1984, made by Mortgagor and recorded in the
Register's Office" and before the phrase "(the "Declaration of Easement")", the
following:

                                       3
<PAGE>
 
     ", as such Declaration of Easement may be modified and amended from time to
     time subsequent to the date hereof with the consent of Mortgagee and, if
     required, the City of New York".

          3.   Modification of Schedule A.  Item 6 of Schedule A, Parcel B, of
               --------------------------                                     
the Consolidation Agreement is hereby amended by deleting the period at the end
thereof and inserting the following:

     ", as further modified by Third Modification to Declaration, dated as of 
     May 30, 1990, by Kenvic Associates, to be recorded in the Register's 
     Office, as such Declaration may be further amended from time to time with
     the consent of the City of New York and Mortgagee."
    
          4.   Representations and Warranties.  The representations and
               ------------------------------                          
warranties contained in Sections 6.01, 6.02, 6.03, 6.04, 6.05, 6.06, 6.07, 6.11
and 6.12 of the Consolidation Agreement are hereby deemed modified so that all
references therein to the Consolidation Agreement shall be deemed to refer to
the Consolidation Agreement as modified by this Modification Agreement and
Mortgagor hereby repeats and reaffirms such representations and warranties as of
the date hereof.

          5.   Ratification.  Except as herein expressly modified, the
               ------------                                           
Consolidation Agreement, and all terms, provisions and covenants thereof, are
and shall remain in full force and effect and are hereby ratified and confirmed.

                                       4
<PAGE>
 
          IN WITNESS WHEREOF, the parties hereto have caused this Modification
Agreement to be duly executed as of the day and year first above written.


                   MORTGAGOR:


                   KENVIC ASSOCIATES, A NEW YORK 
                     GENERAL PARTNERSHIP


                   By:  Gladwater Associates, a New York
                        Limited Partnership, as a
                        General Partner of Kenvic
                        Associates


                        By/s/Kenneth Gladstone
                          ------------------------------------------- 
                              Kenneth Gladstone, 
                              as a General Partner 
                              of Gladwater Associates
                                   

                        By/s/Lucille Gladstone  
                          -------------------------------------------    
                              Lucille Gladstone,
                              as a General Partner 
                              of Gladwater Associates


                   By:  Vic Associates, a New York 
                        Limited Partnership, as a General
                        Partner of Kenvic Associates


                        By General Chemical and Supply 
                          Co., Inc., as General Partner
                          of Vic Associates


                        By/s/ Edwin H. Baker
                          --------------------------------------------
                              Edwin H. Baker
                              President

                                       5
<PAGE>
 
                                   MORTGAGEE:


[Corporate SEAL]                   JOHN HANCOCK MUTUAL LIFE 
                                     INSURANCE COMPANY
 

Attest:                            By /s/ Robert E. Latta
                                      ---------------------------------
                                     Title: Senior Mortgage Investment Officer
 
By /s/ Barry P. Sanborn
   --------------------
  Assistant Secretary

                                       6
<PAGE>
 
                                  SCHEDULE A


                              Description of Land
                              -------------------


                                   Parcel A
                                   --------


          ALL that certain lot, piece or parcel of land, situate, lying and
being in the Borough of Manhattan, City, County and State of New York, bounded
and described as follows:

          BEGINNING at the corner formed by the intersection of the easterly
side of Third Avenue with the northerly side of East 52nd Street; running thence

          NORTHERLY along the easterly line of Third Avenue, 120 feet 5 inches;
thence

          EASTERLY parallel with the northerly line of East 52nd Street, 80 feet
0 inches; thence

          NORTHERLY parallel with the easterly line of Third Avenue, 80 feet 5
inches to a point in the southerly line of East 53rd Street; thence

          EASTERLY along the southerly line of East 53rd Street, 100 feet 0
inches; thence

          SOUTHERLY parallel with the easterly line of Third Avenue, 90 feet 0
inches; thence

          WESTERLY parallel with the northerly line of East 52nd Street, 20 feet
0 inches; thence

          SOUTHERLY parallel with the easterly line of Third Avenue, 110 feet 10
inches to a point in the northerly line of East 52nd Street; thence

          WESTERLY along the northerly line of East 52nd Street, 160 feet 0
inches to the point or place of BEGINNING.
<PAGE>
 
                                   Parcel B
                                   --------


          The rights, licenses, easements and privileges relating to the above-
described parcels of Land which are and have been granted with respect thereto
in the following instruments:

1.   Easement for Light, Air and View, dated January 23, 1981, by and between 
     The Salvation  Army, Kenvic Associates, Arnold J. Rabinor and Marvin B. 
     Tepper, recorded in the Register's Office in Reel 555 at page 1233, as such
     Easement may be further amended from time to time with the consent of 
     Mortgagee and, if required, the City of New York.

2.   Easement for Light and Air, dated January 7, 1981, by Kenvic Associates,
     Arnold J. Rabinor and Marvin B. Tepper, recorded in the Register's Office
     in Reel 555 at page 1245, as such Easement may be further amended from time
     to time with the consent of Mortgagee and, if required, the City of New
     York.

3.   Easement for Light and Air, dated January 5, 1981, by Kenvic Associates,
     Arnold J. Rabinor and Marvin B. Tepper, recorded in the Register's Office
     in Reel 558 at page 460, as such Easement may be further amended from time
     to time with the consent of Mortgagee and, if required, the City of New
     York.

4.   Declaration of Zoning Lot Restrictions, dated January 7, 1981, by Kenvic
     Associates, Arnold J. Rabinor, Marvin B. Tepper and Kenneth Gladstone,
     recorded in the Register's Office in Reel 552 at page 737, as such
     Declaration may be further amended from time to time with the consent of
     the City of New York and Mortgagee.

5.   Declaration, dated January 7, 1981, made by F.E.G. Realty Corp., recorded
     in the Register's Office in Reel 556 at page 539, as such Declaration may
     be further amended from time to time with the consent of the City of New
     York and Mortgagee.

6.   Declaration, dated January 7, 1981, made by Kenvic Associates, Arnold J.
     Rabinor, Marvin B. Tepper and Kenneth Gladstone, recorded in the Register's
     Office in Reel 556 at page 541 and in Reel 556 at page 1281, as modified by
     Modification to Declaration, dated as of June 14, 1982, between Kenvic
     Associates and 875
<PAGE>
 
     Third Associates recorded in the Register's Office in Reel 653 at page 
     1315, as further modified by Second Modification to Declaration, dated as 
     of dated as of December 7, 1983, between Kenvic Associates and 875 Third
     Associates recorded in the Register's Office in Reel 745 at page 533, as
     further modified by Third Modification to Declaration, dated as of May 30,
     1990, by Kenvic Associates, as such Declaration may be further amended from
     time to time with the consent of the City of New York and Mortgagee.

7.   Declaration of Easement, dated July 17, 1984, made by Kenvic Associates,
     and recorded in the Register's Office on July 18, 1984 in Reel 814 at page
     1202, as such Declaration of Easement may be further amended from time to
     time with the consent of Mortgagee and, if required, the City of New York.
<PAGE>
 
                                  SCHEDULE B


          (a)  Mortgage ("Mortgage 1"), dated May 1, 1961, executed by Tillie
Feldman to Raymond A. Hasbrouck, securing a note of even date therewith in the
principal amount of $160,000, recorded in the Register's Office on May 17, 1961,
in Liber 5971, Page 291, Mortgage Tax Paid $800.00;

          (b)  Mortgage ("Mortgage 2"), dated October 3, 1961, executed by
Montor Realty Corp. to Max M. Vas, Sam Wolf and Frances Wolf, securing a note of
even date therewith in the principal amount of $42,300, recorded in the
Register's Office on October 5, 1961, in Liber 6002, Page 12, Mortgage Tax Paid
$291.50;

          (c)  Mortgage ("Mortgage 3"), dated July 31, 1963, executed by Samuel
Gruber to Bankers Life Company, securing a note of even date therewith in the
principal amount of $64,100, recorded in the Register's Office on August 5,
1963, in Liber 6196, Page 37, Mortgage Tax Paid $320.50;

          (d)  Mortgage ("Mortgage 4"), dated March 31, 1970, executed by C.B.B.
Realty Corp. to Cortelyou Realty Corporation, securing a note of even date
therewith in the principal amount of $275,000, recorded in the Register's Office
on March 31, 1970, in Reel 169, Page 1013, Mortgage Tax Paid $2,062.50;

          (e)  Mortgage ("Mortgage 5"), dated December 16, 1959, from Drury Lane
Equities, Inc. to David Fischoff, securing a note of even date therewith in the
principal amount of $17,500, recorded in the Register's Office on December 17,
1959 in Mortgage Book 5866, Page 422, Mortgage Tax Paid $87.50;

          (f)  Mortgage ("Mortgage 6"), dated March 30, 1970, from HMW Holding
Corp. to Hester M. Walsh, securing a note of even date therewith in the
principal amount of $207,000, recorded in the Register's Office on March 31,
1970 in Reel 169, Page 879, Mortgage Tax Paid $1,552.50;

          (g)  Mortgage ("Mortgage 7"), dated August 17, 1945, from Joseph
Renkel, Inc. to Broadway Savings Bank, securing a bond of even date therewith in
the principal amount of $15,000, recorded in the Register's Office on August 18,
1945 in Liber 4762, Page 365, Mortgage Tax Paid $75.00;
<PAGE>
 
          (h)  Mortgage ("Mortgage 8"), dated June 12, 1958, from Joseph Renkel,
Inc. to Broadway Savings Bank, securing a note of even date therewith in the
principal amount of $10,000, recorded in the Register's Office on June 13, 1958
in Mortgage Book 5753, Page 617, Mortgage Tax Paid $50.00;

          (i)  Mortgage ("Mortgage 9"), dated March 12, 1962, from 216 E. 53rd
Street Corp. to Phoenix Mutual Life Insurance Company ("Phoenix Mutual")
securing a note of even date therewith in the principal amount of $42,640,
recorded in the Register's Office on March 15, 1962 in Liber 6039, Page 12,
Mortgage Tax Paid $213.00;

          (j)  Mortgage ("Mortgage 10"), dated July 14, 1964 from 216 E. 53rd
Street Corp. to Phoenix Mutual, securing a note of even date therewith in the
principal amount of $10,000, recorded in the Register's Office on July 15, 1964
in Liber 6299, Page 8, Mortgage Tax Paid $50.00;

          (k)  Mortgage ("Mortgage 11"), dated March 14, 1969, from East 53rd
Street Corporation to Sutton Associates, securing a note of even date therewith
in the principal amount of $146,750, recorded in the Register's Office on March
18, 1969 in Reel 134, Page 413, Mortgage Tax Paid $733.50;

          (1)  Mortgage ("Mortgage 12"), dated May 16, 1955, from J.K.F. Realty
Corporation to Maybelle Stolitzky, Samuel L. Stolitzky and Nathaniel Seligman, 
as Trustees, securing a note of even date therewith in the principal amount of
$43,000, recorded in the Register's Office on May 17, 1955 in Liber 5541, Page
660, Mortgage Tax Paid $215.00;

          (m)  Mortgage ("Mortgage 13"), dated May 16, 1956, from J.K.F. Realty
Corporation to Woman's Division of Christian Service of the Board of Missions of
the Methodist Church ("Woman's Division"), securing a note of even date
therewith in the principal amount of $7,000, recorded in the Register's Office
on May 18, 1956 in Liber 5617, Page 216, Mortgage Tax Paid $35.00;

          (n)  Mortgage ("Mortgage 14"), dated January 26, 1961, from 2187 8th
Avenue Corp. ("2187 Corp.") to Phoenix Mutual, securing a note of even date
therewith in the

                                       2
<PAGE>
 
principal amount of $19,000, recorded in the Register's Office on January 30,
1961 in Liber 5947, Page 487, Mortgage Tax Paid $95.00;

          (0)  Mortgage ("Mortgage 15"), dated May 4, 1956, from Sinne Realty
Corporation ("Sinne") to Theresa White, securing a note of even date therewith
in the principal amount of $23,000, recorded in the Register's Office on May 8,
1956 in Liber 5615, Page 36, Mortgage Tax Paid $115.00;

          (p)  Mortgage ("Mortgage 16"), dated February 11, 1959, from Joseph
Lesawyer and William H. McCarthy to American Irving Savings Bank ("American
Irving"), securing a note of even date therewith in the principal amount of
$14,000, recorded in the Register's Office on February 16, 1959 in Liber 5804,
Page 326, Mortgage Tax Paid $70.00;

          (q)  Mortgage ("Mortgage 17"), dated February 13, 1969, from
Wideningyre Properties Corp. ("Wideningyre") to American Bank & Trust Company,
securing a note of even date therewith in the principal amount of $51,279.49 and
recorded in the Register's Office on February 17, 1969 in Reel 131, Page 428,
Mortgage Tax Paid $256.50;

          (r)  Mortgage ("Mortgage 18"), dated May 27, 1960, from Rupeg Realty
Corp. ("Rupeg") to Chemical Bank New York Trust Company ("Chemical"), securing a
note of even date therewith in the principal amount of $430,000 and recorded in
the Register's Office on May 31, 1960 in Liber 5898, Page 548, Mortgage Tax Paid
$2,150.00;

          (s)  Mortgage ("Mortgage 19"), dated October 27, 1970, from Linguist
Realty Corp. ("Linguist") to Edward W. Leckerling ("Leckerling"), securing a
note of even date therewith in the principal amount of $535,000 and recorded in
the Register's Office on November 2, 1970 in Reel 187, Page 817, Mortgage Tax
Paid $4,012.50;

          (t)  Mortgage ("Mortgage 20"), dated November 16, 1962, from Montclair
Leasing Corp. ("Montclair") to Chemical, securing a note of even date therewith
in the principal amount of $292,500 and recorded in the Register's Office on
November 23, 1962 in Liber 6110, Page 462, Mortgage Tax Paid $1,462.50;

                                       3
<PAGE>
 
          (u)   Mortgage ("Mortgage 21"), dated January 20, 1972, from Dorell
Properties, Inc. to Jack D. Roggen ("Roggen") and Ruth Baron ("Baron"), securing
a note of even date therewith in the principal amount of $560,619.64, and
recorded in the Register's Office on January 21, 1972 in Reel 229, Page 1244,
Mortgage Tax Paid $7,007.50;

          (v)   Mortgage ("Mortgage 22"), dated December 20, 1957, from 937
Madison Ave. Corp. to The Amalgamated Bank of New York ("The Amalgamated Bank"),
securing a note of even date therewith in the principal amount of $30,000,
recorded in the Register's Office on December 23, 1957 in Liber 5722, Page 18,
Mortgage Tax Paid $150.00;

          (w)   Mortgage ("Mortgage 23"), dated January 21, 1963, from 937
Madison Ave. Corp. to The Amalgamated Bank, securing a note of even date
therewith in the principal amount of $18,934.52, recorded in the Register's
Office on January 22, 1963 in Liber 6131, Page 263, Mortgage Tax Paid $94.50;

          (x)   Mortgage ("Mortgage 24"), dated July 26, 1971, from Vertland
Realty Corp., Reba Associates, Inc., Woas Properties Corp., JL 229 Corp.,
Portadown Corporation, Wideningyre Properties and Zalkay Properties, Inc. to
Salbian Realty Co., Inc., securing a note of even date therewith in the
principal amount of $5,000,000, recorded in the Register's Office on July 28,
1971 in Reel 212, Page 814, Mortgage Tax Paid $37,500.00;

          (y)   Mortgage ("Mortgage 25"), dated July 18, 1972, from Siltan
Development Corp. and Mathilde Rauch to Irving Trust Company, securing a note of
even date therewith in the principal amount of $1,514,390.19, recorded in the
Register's Office on July 21, 1972 in Reel 247, Page 639, Mortgage Tax Paid
$18,930.00;

          (z)   Mortgage ("Mortgage 26"), dated August 11, 1975, from Siltan
Development Corp. and Mathilde Rauch to Tishman Realty & Construction Co., Inc.,
securing a note of even date therewith in the principal amount of $675,000,
recorded in the Register's Office on August 15, 1975 in Reel 348, Page 1342,
Mortgage Tax Paid $8,437.50;

          (aa)  Building Loan Mortgage ("Mortgage 27"), dated as of November 24,
1980, executed by Kenvic As-

                                       4
<PAGE>
 
sociates ("Kenvic"), Arnold J. Rabinor and Marvin B. Tepper to The Chase
Manhattan Bank (National Association) ("Chase"), securing a note of even date
therewith in the principal amount of $3,165,000, recorded in the Register's
Office on November 26, 1980, in Reel 545, Page 905, Mortgage Tax Paid
$47,475.00;

          (bb)  Building Loan Mortgage ("Mortgage 28"), dated as of March 3,
1981, executed by Kenvic to Chase, securing a note of even date therewith in the
principal amount of $2,500,000, recorded in the Register's Office on March 12,
1981, in Reel 558, Page 413, Mortgage Tax Paid $37,500.00;

          (cc)  Building Loan Mortgage ("Mortgage 29"), dated as of March 25,
1981, executed by Kenvic and 875 Third Associates ("875") to Chase, securing a
note of even date therewith in the principal amount of $38,660,000, recorded in
the Register's Office on April 2, 1981, in Reel 560, page 1577, Mortgage Tax
Paid $579,900.00;

          (dd)  Building Loan Mortgage ("Mortgage 30"), dated as of March 25,
1981, executed by Kenvic and 875 to Chase, securing a note of even date
therewith in the principal amount of $14,000,000, recorded in the Register's
Office on April 2, 1981, in Reel 560, Page 1527, Mortgage Tax Paid $210,000.00;

          (ee)  Building Loan Mortgage ("Mortgage 31"), dated as of March 25,
1981, executed by Kenvic and 875 to Chase, securing a note of even date
therewith in the principal amount of $3,750,000, recorded in the Register's
Office on April 2, 1981, in Reel 560, Page 1728, Mortgage Tax Paid $56,250.00;

          (ff)  Building Loan Mortgage ("Mortgage 32"), dated as of March 25,
1981, executed by 875 and Kenvic to Chase, securing a note of even date
therewith in the principal amount of $3,750,000, recorded in the Register's
Office on April 2, 1981, in Reel 560, Page 1764, Mortgage Tax Paid $56,250.00;

          (gg)  Mortgage ("Mortgage 33"), dated as of September 2, 1982,
executed by 875 and Kenvic to Chase, securing a note of even date therewith in
the principal amount of $12,000,000, recorded in the Register's Office on
September 8, 1982, in Reel 637, Page 1657, Mortgage Tax Paid $270,000.00;

                                       5
<PAGE>
 
          (hh)  Mortgage ("Mortgage 34"), dated as of August 5, 1983, executed
by 875 and Kenvic to Chase, securing a note of even date therewith in principal
amount of $2,000,000, recorded in the Register's Office on August 26, 1983, in
Reel 712, Page 980, Mortgage Tax Paid $45,000.00;

          (ii)  Mortgage ("Mortgage 35"), dated as of October 5, 1983, executed
by 875 and Kenvic to Chase, securing a note of even date therewith in principal
amount of $925,000, recorded in the Register's Office on October 6, 1983, in
Reel 724, Page 463, Mortgage Tax Paid $20,812.50;

          (jj)  Mortgage ("Mortgage 36"), dated as of November 28, 1983,
executed by 875 and Kenvic to Chase, securing a note of even date therewith in
principal amount of $3,325,000, recorded in the Register's Office on December 5,
1983, in Reel 742, Page 150, Mortgage Tax Paid $74,812.50;

          (kk)  Mortgage ("Mortgage 37"), dated as of November 28, 1983,
executed by 875 and Kenvic to Chase, securing a note of even date therewith in
principal amount of $750,000, recorded in the Register's Office on December 5,
1983, in Reel 742, Page 122, Mortgage Tax Paid $16,875.00;

          (ll)  Mortgage ("Mortgage 38"), dated as of February 24, 1984,
executed by 875 and Kenvic to Chase, securing a note of even date therewith in
principal amount of $4,000,000, recorded in the Register's Office on February
27, 1984, in Reel 767, Page 1542, Mortgage Tax Paid $90,000.00;

          (mm)  Mortgage ("Mortgage 39"), dated as of July 17, 1984, executed by
Kenvic to John Hancock Mutual Life Insurance Company ("Hancock"), securing a
note of even date therewith in the principal amount of $13,000,000, recorded in
the Register's Office on July 18, 1984, in Reel 814, Page 1248, Mortgage Tax
Paid $292,500.00;

          (nn)  Mortgage ("Mortgage 40"), dated as of May 11, 1988, from
Mortgagor to Hancock, securing a note dated May 12, 1988, in the original
principal amount of $71,339,564.68, recorded in the Register's Office on

                                       6
<PAGE>
 
================================================================================

                               KENVIC ASSOCIATES,

                                    Mortgagor,

                                      and

                 JOHN HANCOCK MUTUAL LIFE INSURANCE COMPANY, Mortgagee.


                      CHICAGO TITLE INSURANCE COMPANY (3)

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

                            MODIFICATION AGREEMENT

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

                           Dated as of May 30, 1990



This instrument affects real and personal property situated in the State of New
York, in Section 5, Block 1326, Lots '1, 7 and 41 on the Tax Map of the County
of New York and easement rights over Lots 45 and 47 on said Tax Map.

RECORD AND RETURN TO:  

    Peter R. Schwartz, Esq.
    Debevoise & Plimpton
    875 Third Avenue
    New York, New York 10022
<PAGE>
 
STATE OF NEW YORK    )
                     :  ss.:
COUNTY OF NEW YORK   )

          On this 31st day of May, 1990, before me personally came Edwin H.
Baker, to me known, and who, being duly sworn by me, did depose and say that he
resides at 21 Alta Lane Chafpaqua: that he is the President of General/Chemical
and Supply Co., Inc., a Delaware corporation, the General Partner of Vic
Associates, a Limited Partnership duly organized under the laws of the State of
New York, having its principal place of business at Gordon Hurwitz Detowday,
Clat, 101 Park Avenue, N.Y, N.Y 10178 ; that Vic Associates is a General Partner
of KENVIC ASSOCIATES, a General Partnership duly organized under the laws of the
State of New York, having its principal place of business at 875 Third Avenue,
New York, New York 10022; that General Chemical and Supply Co., Inc., acting as
a General Partner of, and in behalf of, Vic Associates, acting as a General
Partner of, and for and in behalf of, KENVIC ASSOCIATES executed the foregoing
instrument as the act and deed of said firms for the uses and purposes therein
mentioned.


                                   /s/ Stephen Helman
                                   ----------------------------------
                                            Notary Public

[Notarial Seal)                        STEPHEN HELMAN                     
---------------                  NOTARY PUBLIC, STATE OF NEW YORK
                                         NO. 4735750
                                     QUALIFIED IN QUEENS COUNTY         
                                   COMMISSION EXPIRES APRIL 30, 1991   

                                       7
<PAGE>
 
STATE OF NEW YORK    ) 
                     : ss.:
COUNTY OF NEW YORK   )

          On this 31st day of May, 1990, before me personally came Kenneth
Gladstone and Lucille Gladstone, to me known to be the persons who executed the
foregoing instrument, and who, being duly sworn by me, did depose and say that
they are the General Partners of Gladwater Associates, a Limited Partnership
duly organized under the laws of the State of New York, having its principal
place of business at 875 Third Avenue, New York, New York 10022; that said
Limited Partnership is a General Partner of KENVIC ASSOCIATES, a General
Partnership duly organized under the laws of the State of New York, having its
principal place of business at 875 Third Avenue, New York, New York 10022; and
that they have authority to sign the foregoing instrument in the firm name of
Gladwater Associates, as a General Partner of, and for and in behalf of, KENVIC
ASSOCIATES, and they acknowledged to me that they executed the same as the act
and deed of said firms for the uses and purposes therein mentioned.


                                  /s/ Ann V. Maschin
                                  ---------------------------------------
                                           Notary Public

[Notarial Seal)                         ANN V. MASCHIN
 -------------                  NOTARY PUBLIC, STATE OF NEW YORK 
                                     NO. 41-4953299       
                                  QUALIFIED IN QUEENS COUNTY
                                COMMISSION EXPIRES................ 
                                   
                                   
<PAGE>
 
COMMONWEALTH OF MASSACHUSETTS    )
                                 :  ss.:
COUNTY OF SUFFOLK                )

          On this 4th day of June, 1990, before me personally came Robert E.
Latham, to me known to be the person who executed the foregoing instrument, and
who, being duly sworn by me, did depose and say that he resides at 590 Essex
Street, Weymouth, Massachusetts, that he is Senior Mortgage Investment Officer
of JOHN HANCOCK MUTUAL LIFE INSURANCE COMPANY, the corporation described in
which executed the foregoing instrument; that he knows the seal of said
corporation; that the seal affixed to said instrument is such corporate seal;
that it was so affixed by order of the Board of Directors of said corporation,
and that he signed his name thereto by like order.

                                   /s/ Marie C. O'Brien
                                   ------------------------------
                                         Notary Public

[Notarial Seal]                     MARIE C. O'BRIEN, NOTARY PUBLIC
 -------------                     MY COMMISSION EXPIRES AUGUST 9, 1996
                                        
<PAGE>
 
May 18, 1988, in Reel 1403 at Page 1779, Mortgage Tax Paid $1,605,141.00; and

          (00)  All of the above mortgages numbered 1 to 40 inclusive were,
pursuant to a Consolidation, Extension and Modification Agreement, dated as of
May 11, 1988, between Kenvic Associates and Hancock, consolidated into one
mortgage lien for $180,000,000.00, recorded in the Register's office on May 18,
1988 in Reel 1403 at Page 1793.

                                       7
