Exhibit 5.1






                                November 20, 1997



Board of Directors
SunPharm Corporation
4651 Salisbury Road, Suite 205
Jacksonville, Florida 32256

Gentlemen:

             We have acted as counsel to SunPharm Corporation (the "Company") in
connection  with  the  Company's   Registration   Statement  on  Form  S-3  (the
"Registration  Statement") relating to the registration under the Securities Act
of 1993, as amended (the "Securities Act"), of the offer and sale by the Selling
Stockholders  identified in the Registration Statement of up to 56,920 shares of
the Common Stock, par value $.001 per share ("Common Stock"), of the Company are
issuable upon the exercise of certain  outstanding options (the "Option Shares")
and up to 2,000  shares of Common  Stock  issuable  upon the exercise of certain
outstanding warrants ("Warrant Shares").

             As the  basis  for  the  opinions  hereinafter  expressed,  we have
examined  such   statutes,   regulations,   corporate   records  and  documents,
certificates of corporate and public officials, and other instruments as we have
deemed  necessary  or  advisable.  In  such  examination  we  have  assumed  the
authenticity  of all documents  submitted to us as originals and the  conformity
with the original documents of all documents submitted to us as copies.

             Based on the foregoing and on such legal  considerations as we deem
relevant,  we are of the opinion that the Option Shares and Warrant  Shares have
been duly and validly  authorized,  and when  issued  upon the  exercise of such
options  and  warrants in  accordance  with the terms  thereof,  will be validly
issued, fully paid and nonassessable.

             We hereby  consent to the use of this  opinion as an exhibit to the
Registration  Statement  and  reference  to our firm  under the  caption  "Legal
Matters" in the Prospectus included therein.

                                            Very truly yours,


                                            /s/ ANDREWS & KURTH L.L.P.
                                            -----------------------------
                                                Andrews & Kurth L.L.P.