EXHIBIT 5.1

                                                                April 30, 2007

MacroChem Corporation
40 Washington Street, Suite 220
Wellesley Hills, MA 02481

Ladies and Gentlemen:

This opinion is furnished to you in connection with a registration statement on
Form S-8 (the "Registration Statement"), filed with the Securities and Exchange
Commission under the Securities Act of 1933, as amended, for the registration of
an aggregate of 2,302,142 shares of Common Stock, $0.01 par value (the
"SHARES"), of MacroChem Corporation, a Delaware corporation (the "COMPANY"), of
which:

         (i) 1,345,238 are issuable under the Company's 2001 Incentive Plan (the
         "PLAN");

         (ii) 11,904 are issuable upon the exercise of that certain stock option
         awarded to Robert J. DeLuccia on June 20, 2003 as an inducement to his
         accepting employment with the Company;

         (iii) 45,000 are issuable upon the exercise of that certain stock
         option awarded to John L. Zabriskie on February 10, 2006 in connection
         with his service as a director of the Company;

         (iv) 45,000 are issuable upon the exercise of that certain stock option
         awarded to Michael A. Davis on February 10, 2006 in connection with his
         service as a director of the Company;

         (v) 45,000 are issuable upon the exercise of that certain stock option
         awarded to Jeffrey B. Davis on February 10, 2006 in connection with his
         service as a director of the Company;

         (vi) 45,000 are issuable upon the exercise of that certain stock option
         awarded to Howard S. Fischer on February 10, 2006 in connection with
         his service as a director of the Company;

         (vii) 45,000 are issuable upon the exercise of that certain stock
         option awarded to Paul S. Echenberg on February 10, 2006 in connection
         with his service as a director of the Company;

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         (viii) 45,000 are issuable upon the exercise of that certain stock
         option awarded to Peter G. Martin on February 10, 2006 in connection
         with his service as a director of the Company;

         (ix) 350,000 are issuable upon the exercise of that certain stock
         option awarded to Robert J. DeLuccia on February 10, 2006 in connection
         with his service as an executive officer of the Company;

         (x) 175,000 are issuable upon the exercise of that certain stock option
         awarded to Bernard R. Patriacca on February 10, 2006 in connection with
         his service as an executive officer of the Company; and

         (xi) 150,000 are issuable upon the exercise of that certain stock
         option awarded to Glenn E. Deegan on February 10, 2006 in connection
         with his service as an executive officer of the Company.

         The option certificates pursuant to which the options in items (ii)
through (xi) above were issued are referred to herein as the "OPTION
CERTIFICATES".

We are familiar with the actions taken by the Company in connection with the
adoption of the Plan and the Option Certificates. For purposes of our opinion,
we have examined and relied upon such documents, records, certificates and other
instruments as we have deemed necessary. The opinions expressed below are
limited to the Delaware General Corporation Law, including the applicable
provisions of the Delaware Constitution and the reported cases interpreting
those laws.

Based on the foregoing, we are of the opinion that the Shares have been duly
authorized and, when the Shares have been issued and sold in accordance with the
terms of the Plan and the Option Certificates, the Shares will be validly
issued, fully paid and nonassessable.

We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement. Our consent shall not be deemed an admission that we are
experts whose consent is required under Section 7 of the Securities Act of 1933.

It is understood that this opinion is to be used only in connection with the
offer and sale of Shares while the Registration Statement is in effect.

Very truly yours,

/s/ Ropes & Gray LLP

Ropes & Gray LLP


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