EXHIBIT 3.3

                              DORSEY & WHITNEY LLP
                               COUNSELORS AT LAW
                                250 Park Avenue
                               New York, NY 10177
                              Writer's Direct Dial
                                 (212) 415-9286
                              Fax: (212) 953-7201



                                  April 9, 2008


The Bank of New York, As Trustee
Van Kampen Unit Trusts, Series 751
2 Hanson Place
12th Floor
Brooklyn, NY 11217


Ladies and Gentlemen:

   We are acting as your counsel in connection with the execution and delivery
by you of a certain trust agreement, dated as of today (the "Indenture"), among
Van Kampen Funds Inc., as depositor (the "Depositor"), Van Kampen Asset
Management, as supervisor (the "Supervisor"), and you, as Trustee, establishing
Van Kampen Unit Trusts, Series 751 (the "Fund"), consisting of S&P Dividend
Growth Opportunities Trust, Series 12 (the "Trust"), and the execution by you,
as trustee under the Indenture, of a certificate or certificates evidencing
ownership of all of the units of fractional undivided interests (such
certificate or certificates and such units being herein respectively called
"Certificates" and "Units") in the Trust, as set forth in the prospectus, dated
today, for filing as an amendment to the registration statement heretofore filed
with the Securities and Exchange Commission under the Securities Act of 1933, as
amended (respectively the "Prospectus" and the "Registration Statement"),
relating to the Fund (File Number 333-149515). The Trust consists of the
securities set forth in the Prospectus including delivery statements relating to
contracts for the purchase of certain securities not yet delivered and cash,
cash equivalents, an irrevocable letter of credit, or a combination thereof, in
the amount required to pay for such purchase upon the receipt of such
securities) defined in the Indenture as "Securities" and listed in Schedule A to
the Indenture (such securities, delivery statements and cash, cash equivalents
or letter of credit being herein called the "Underlying Securities").

   We have examined the Indenture, specimen Certificates and originals (or
copies certified or otherwise identified to our satisfaction) of such other
instruments, certificates and documents, as we have deemed necessary or
appropriate for the purpose of rendering this opinion letter. In such
examination, we have assumed the genuineness of all signatures, the authenticity
of all documents submitted to us as originals and the conformity to the original
documents of all documents submitted to us as copies. As to any facts material
to this opinion letter, we have, when relevant facts were not independently
established, relied upon the aforesaid instruments, certificates and documents.

   Based on the foregoing, we are of the opinion that:

     1.   The Bank of New York is a corporation organized under the laws of the
          State of New York with the powers of a trust company under the Banking
          Law of the State of New York.

     2.   The execution of the Indenture is within the authorization of the
          executing officers of The Bank of New York.

     3.   The Indenture in proper form for execution and delivery by you as
          Trustee.

     4.   The Certificates are in proper form for execution and delivery by you
          as Trustee.

     5.   Upon receipt by you of the Underlying Securities you may properly
          execute Certificates or statements evidencing ownership of the Units,
          registered in the name of the Depositor, and upon receipt of advice of
          the effectiveness of the Registration Statement, you may deliver such
          Certificates or statements to or upon the order of the Depositor as
          provided in the Closing Memorandum being executed and delivered today
          by the parties to the Indenture.

     6.   You as Trustee may lawfully, under the Banking Law of the State of New
          York, advance to the Trust such amounts as may be necessary to provide
          periodic distributions or payment of expenses for the Trust, and be
          reimbursed without interest for any such advance from funds in the
          income or capital account for the Trust on the ensuing record date or
          as otherwise provided in the Indenture.

   In rendering the foregoing opinions we have not considered, among other
things, the merchantability of the Underlying Securities, whether the Underlying
Securities have been duly authorized and delivered and are fully paid for and
non-assessable or the tax status of the Underlying Securities under any federal,
state or local laws.

   The foregoing opinions are limited to the laws of the State of New York and
the federal laws of the United States of America.

   We hereby consent to the filing of this opinion letter as an exhibit to the
Registration Statement and to the use of our name and the reference to our firm
in the Registration Statement and in the Prospectus.



                                                               Very truly yours,


                                                       /s/ Dorsey & Whitney, LLP