Enantiocomplementary preparation of (S)- and (R)-mandelic acid derivatives via α-hydroxylation of 2-arylacetic acid derivatives and reduction of α-ketoester using microbial whole cells

Forty one microorganisms belonging to different taxonomical groups were used to carry out the enantioselective reduction of methyl benzoylformate to afford the corresponding (R)-methyl mandelate, with moderate to high ee. In contrast, the monooxygenase enzyme in Helminthosporium sp. CIOC3.3316 catalyzed the hydroxylation of methyl 2-phenylacetate to (S)-methyl mandelate. This combination of oxidation and reduction biotransformations thus provides a method for preparing the enantiomers of chiral α-hydroxy acid derivatives.

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(S)-Methyl mandelateC9H10O3[α]D20=+130.2 (c 0.8, methanol)Absolute configuration: (S)