Bioreductive production of enantiopure (S)-duloxetine intermediates catalyzed with ketoreductase ChKRED15

Abstract The blockbuster antidepressant drug duloxetine contains one stereo-center derived from chiral alcohol intermediates. The stereoselective bioreductive production of five of such intermediates could be achieved using the recombinant ketoreductase Ch KRED15, yielding the enantiopure ( S )-alcohols with >99% ee. Sequence alignment indicated that Ch KRED15 lacks the conserved G-rich motif, which was then amended by a single mutation of S12G. The resulting S12G mutant displayed significantly improved catalytic activity and protein stability. When coupled with a cofactor recycling system, the S12G mutant was able to catalyze the complete conversion of ethyl 3-oxo-3-(thiophen-2-yl)propanoate within 6 h and N -methyl-3-oxo-3-(thiophen-2-yl)propanamide within 24 h at substrate concentrations of 10 and 50 g/l, respectively, without the compromise of enantioselectivity.