Highly regio- and enantioselective reduction of 1-chloro-2,4-alkanediones using baker's yeast: Effects of organic solvents as additives

Bakers' yeast reduction of 1-chloro-2,4-alkanediones 1a afforded 1-chloro-2-hydroxy-4-alkanones 2a regioselectively with low optical purities. Application or inhibitors and heal-treatment of bakers' yeast enhanced the optical purities toward the S enantiomer (88-91% ee). Organic solvents added in small amounts were also found to enhance the S selectivity significantly. High optical purities of 94-96% ee were achieved by the combined action of the inhibitor, heat-treatment, and organic solvent. (C) 1997 Elsevier Science Ltd.