Cartesian -to- z-matrix conversion

 I hope that this isn't a FAQ, but I would like to convert
 a file containing a molecule's geometry in the form of
 cartesian coordinates to a z-matrix.  (Specifically, I
 have a Sybyl .mol2 file for a polypeptide that is too big
 for the z-matrix converter that is already available in
 Sybyl.)  Is there anyone on the bulletin board who would
 be willing to share his or her program with me to do this
 task?  It does not matter to me whether I may need to
 modify your program if it had been written originally for
 files from another software system.  As long as it takes
 a cartesian geometry and generates a z-matrix, I'll be
 grateful for your help.
 Anthony J. Duben
 Center for Molecular Design
 Washington University
 Campus Box 1099
 One Brookings Drive
 St. Louis MO 63130-4899
 tony #*at*#