Biotransformations for the production of the chiral drug (S)-Duloxetine catalyzed by a novel isolate of Candida tropicalis.

A yeast strain, Candida tropicalis PBR-2, isolated from soil, is capable of carrying out the enantioselective reduction of N,N-dimethyl-3-keto-3-(2-thienyl)-1-propanamine to (S)-N,N-dimethyl-3-hydroxy-3-(2-thienyl)-1-propanamine, a key intermediate in the synthesis of the chiral drug (S)-Duloxetine. The organism produced the enantiopure (S)-alcohol with a good yield (> 80%) and almost absolute enantioselectivity, with an enantiomeric excess (ee) > 99%. Parameters of the bioreduction reaction were optimized and the optimal temperature and pH for the reduction were found to be 30 degrees C and 7.0, respectively. The optimized substrate and the resting cell concentration were 1 g/l and 250 g/l, respectively. The preparative-scale reaction using resting cells of C. tropicalis yielded the (S)-alcohol at 84-88% conversion and ee > 99%.