Asymmetric syntheses of the enantiomerically pure trifunctional (R)-3-hydroxyesters (7)–(10) can be achieved by baker'syeastreduction of the hydrolysed β-keto carboxylates (2)–(5) instead of by reduction of the corresponding ester.
Stereochemistry of the reduction of β-keto esters with bakers’ yeast is controlled by the addition of a certain α,β-unsaturated carbonyl compound (or its reduced form). Glucose also exerts the same effect. The additives tend to shift the stereochemistry of the reduction toward the production of D-hydroxy ester. Namely, methyl 3-oxopentanoate and ethyl 3-oxo-6-heptenoate were reduced to the corresponding