Exhibit 5.1


                             ANDREWS & KURTH L.L.P.
                        2170 BUCKTHORNE PLACE, SUITE 150
                           THE WOODLANDS, TEXAS 77380


                                 April 23, 1999



Board of Directors
SunPharm Corporation
The Veranda, Suite 301
814 Highway A1A
Ponte Vedra Beach, Florida  32082

Ladies and Gentlemen:

                 We have acted as counsel to  SunPharm  Corporation,  a Delaware
corporation,  (the "Company")  in  connection  with the  Company's  Registration
Statement  on  Form  S-8  (the   "Registration   Statement")   relating  to  the
registration  under the  Securities  Act of 1933,  as amended,  of an additional
200,000 shares (the "Shares") of the Company's  common stock,  $.0001 par value,
to be issued  pursuant  to SunPharm  Corporation's  Amended  and  Restated  1995
Non-employee Directors' Stock Option Plan (the "Plan").

                 As a basis  for the  opinions  hereinafter  expressed,  we have
examined copies of such statutes, regulations,  corporate records and documents,
certificates of public and corporate officials and other agreements,  contracts,
documents and  instruments  as we have deemed  necessary for the purposes of the
opinions contained herein. In such examination,  we have assumed the genuineness
of  all  signatures,  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.  We have also  relied,  to the  extent we deem such
reliance  proper,  on  information  supplied by officers  and  employees  of the
Company with respect to various factual matters material to our opinion.

                 Based on the  foregoing  and  having  due regard for such legal
considerations  as we deem relevant,  we are of the opinion that the Shares have
been duly  authorized,  and that such Shares  will,  when issued and paid for in
accordance  with the  terms of the  Plan,  be  legally  issued,  fully  paid and
nonassessable.

                 The foregoing opinion is based on and is limited to the General
Corporation  Law of the State of Delaware and the  relevant  federal laws of the
United  States of America,  and we render no opinion with respect to the laws of
any other jurisdiction.

                 We hereby  consent to the use of this  opinion as an exhibit to
the Registration Statement.

                                            Very truly yours,


                                            ANDREWS & KURTH L.L.P.

1536/2610