EXHIBIT 10.16b

                First Amendment to Agreement of Purchase and Sale
                -------------------------------------------------
                            (KELLOGG OFFICE BUILDING)

     This First Amendment to Agreement of Purchase and Sale ("First Amendment")
is entered into effective as of November 29, 2001 by and between WXI/MCN
Commercial Real Estate Limited Partnership, a Delaware limited partnership
("Seller") and AmeriVest Properties Inc., a Maryland corporation ("Purchaser").

                                    RECITALS
                                    --------

     WHEREAS, the parties entered into that certain Agreement of Purchase and
Sale ("Agreement") dated October 15, 2001, for the sale of the real property
commonly known as the Kellogg Office Building in Littleton, Colorado
("Property");

     WHEREAS, the Agreement provides for a forty-five (45) day Inspection Period
and a Closing Date of December 28, 2001;

     WHEREAS, the parties now desire to amend the Agreement as set forth herein.

     NOW, THEREFORE, in consideration of the mutual terms and provisions set
forth in the Agreement, the sums to be paid by Purchaser to Seller and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Purchaser and Seller agree to amend the Agreement as follows:

     1.   The parties hereto agree that as of the effective date of this
          Amendment, both the Inspection Period and Title and Survey Period have
          expired, and Purchaser has elected to proceed to Closing on or before
          December 28, 2001, subject to Seller's satisfaction of the Estoppel
          Contingency (and Purchaser's approval of same) and the Maintenance
          Obligations, both as set forth below.

     2.   On or before December 12, 2001 ("Estoppel Delivery Deadline"), Seller
          shall deliver the tenant estoppel certificates ("Estoppel
          Certificates") to Purchaser in accordance with the provisions of
          Section 4.4 of the Agreement ("Estoppel Contingency"). For a period of
          no more than two (2) business days following Purchaser's receipt of
          all of the Estoppel Certificates from Seller ("Estoppel Review
          Period"), Purchaser shall have the right to review the number, form
          and content of such Estoppel Certificates. In the event (i) Purchaser
          is not satisfied, in its sole and absolute discretion, with any lesser
          number of Estoppel Certificates than the amount Seller is obligated to
          deliver, (ii) any such Estoppel Certificate delivered by Seller is not
          duly executed by the applicable tenant referenced therein, or (iii)
          the form and content of any such Estoppel Certificate delivered by
          Seller materially differs from the form of tenant estoppel certificate
          attached to the Agreement, Purchaser shall have the right to terminate
          the Agreement by delivering written notice of termination to Seller
          and the Escrow Agent on or before the expiration of the Estoppel

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          Review Period. If Seller does not receive such written notice of
          termination from Purchaser prior to the expiration of the Estoppel
          Review Period, Purchaser shall be deemed to have approved the Estoppel
          Certificates and the Estoppel Contingency shall be deemed satisfied.

     3.   Prior to Closing, Seller hereby agrees to either: (i) repair on or
          before the Closing Date the following maintenance items relating to
          the Building (the following maintenance items shall be collectively
          referred to herein as the "Maintenance Obligations") (x) replacement
          of the glass panels wherever panels or window seals are broken in
          Suites 160 and 250 of the Building, and (y) installation of backflow
          prevention devices on all water service lines of the Building as
          required by Denver Water Company, which repairs shall be diligently
          performed to Purchaser's satisfaction at least two (2) business days
          prior to Closing; or (ii) credit Purchaser at Closing in a mutually
          agreeable amount for the estimated cost to repair one or both
          Maintenance Obligations, to the extent one or both cannot be
          completely repaired to Purchaser's satisfaction prior to the Closing
          Date.

     4.   Except as expressly amended under this Amendment, all the terms and
          provisions of the Agreement shall remain in full force and effect
          without any modification, waiver or amendment thereto. To the extent
          of any conflict between the terms and provisions of the Agreement and
          this Amendment, the terms and provisions of this Amendment shall
          govern and control.

     5.   All terms which are defined in the Agreement shall have the same
          meaning when used in this Amendment, unless specifically provided
          herein to the contrary.

     6.   This Amendment may be executed in separate counterparts, each of which
          shall constitute an original and all of which, when taken together,
          shall constitute one and the same instrument. In addition, Seller and
          Purchaser agree that facsimile signatures on this Amendment shall be
          deemed effective as originals for all purposes.

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     IN WITNESS WHEREOF, the parties hereto have executed this Amendment to be
effective as of the date first written above.

                                            SELLER:
                                            -------

                                            WXL/MCN Commercial Real Estate
                                            Limited Partnership, a Delaware
                                            limited partnership

                                            By: WXI/MCN Commercial Gen-Par, LLC,
                                                a Delaware limited liability
                                                company, its General Partner


                                            By:  /s/  Marijke Lantz
                                               --------------------------------
                                            Name:     Marijke Lantz
                                                 ------------------------------
                                            Title: Assistant Vice President
                                                  -----------------------------

                                            PURCHASER:
                                            ----------

                                            AMERIVEST PROPERTIES INC.
                                            a Maryland Corporation


                                            By:  /s/  John B. Greenman
                                               --------------------------------
                                                      John B. Greenman
                                                      Vice President

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