Enantioselective Biocatalytic Reduction of 1-(4-Fluorophenyl)ethanone

Enantioselective reduction of 1-(4-fluorophenyl)ethanone, catalyzed by P. crispum cells, was studied. Conditions that allow obtaining (S)-(–)-1-(4-fluorophenyl)ethanol by bioreduction of 1-(4-fluorophenyl)ethanone in the presence of a P. crispum biocatalyst for 48 h with a 46% yield (90% ee) were found. The possibility of optimizing the conditions for the biotransformation of 1-(4-fluorophenyl)ethanone in a reaction medium containing exogenous reducing agents (ethanol, isopropanol, or glucose) was studied. It was revealed that the bioreduction of 1-(4-fluorophenyl)ethanone in the presence of ethanol, isopropanol (1‒5%), or of an equimolar amount of glucose as an exogenous reducing agent mainly leads to the formation of an S-alcohol with moderate yields and optical purities. However, bioreduction of 1-(4-fluorophenyl)ethanone in the presence of 4 and 5% of isopropanol during 144 h leads to the (R)-enantiomer of 1-(4-fluorophenyl)ethanol with the respective yields of 50 and 76% and optical purities of 14 and 20% ee.