Enzymatic kinetic resolution of racemic ketones catalyzed by Baeyer–Villiger monooxygenases

A set of racemic cyclic and linear ketones, as well as 2-phenylpropionaldehyde, were tested as substrates in the enzymatic Baeyer–Villiger oxidation catalyzed by two Baeyer–Villiger monooxygenases: phenylacetone monooxygenase (PAMO) and 4-hydroxyacetophenone monooxygenase (HAPMO). Excellent enantioselectivites (E > 200) can be obtained in the kinetic resolution processes depending on the substrate structure and the reaction conditions. The parameters affecting the biocatalytic properties of these enzymes were also studied, in order to establish a deeper understanding of these novel biocatalysts.

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(R)-2-Phenylpentan-3-oneC11H14OEe = 95% (GC, RtβDEXse)[α]D25=-76.4 (c 1.20, CHCl3)Source of chirality: enzymatic oxidationAbsolute configuration: (R)

(R)-4-Phenylhexan-3-oneC12H16OEe = 98% (GC, RtβDEXse)[α]D25=-61.2 (c 0.75, CHCl3)Source of chirality: enzymatic oxidationAbsolute configuration: (R)

(S)-1-Phenylpropyl propionateC12H16O2Ee = 90% (GC, RtβDEXse)[α]D25=-41.7 (c 0.83, CHCl3)Source of chirality: enzymatic oxidationAbsolute configuration: (S)