Microbial models of mammalian metabolism: stereospecificity of ketone reduction with pentoxifylline.

The absolute configuration of pentoxifylline alcohol produced by the microbial reduction of pentoxifylline using Rhodotorula rubra (ATCC 20129) was determined by O.R.D. spectroscopy and p.m.r. studies on the R-(+)-alpha-methoxy-alpha-(trifluoromethyl) phenylacetate (MTPA) ester. The development of a reverse-phase h.p.l.c. method for resolving the diastereomeric R-(+)-MTPA esters of racemic pentoxifylline alcohol and assignment of the elution order, allowed for the determination of the stereochemical purity of pentoxifylline alcohol produced by 13 microbial cultures shown previously to reduce pentoxifylline. A marked preference for S-alcohol production was observed with five organisms exhibiting complete stereoselectivity towards S-alcohol generation, and two producing the racemic alcohol.