diastereoselectivity in a bakers’ yeastreduction of various alkyl 2-alkyl-3-oxoalkanoates can be controlled by a thermal treatment of the yeast in the presence of methyl vinyl ketone. Pretreated bakers’ yeast gives the corresponding (2R,3S)-hydroxy esters selectively. Two β-keto ester reductases, named L-enzyme-1 and L-enzyme-2, are actual reductants of intact bakers’ yeastreduction. The thermal stability
Various β-keto esters have been reduced by one of β-keto ester reductases isolated frombakers’ yeast. The corresponding β-hydroxy esters have been obtained in excellent enantiomeric and diastereomeric excesses, respectively. It has also been elucidated that the reductase recognizes the stereochemistry not only at the β-carbon but also at the α-carbon affording one of the four possible diastereoisomers