Enzyme-Catalyzed Asymmetric Synthesis; 10.¹ Pseudomonas cepacia Lipase Mediated Synthesis of Enantiomerically Pure (2R,3S)- and (2S,3R)-2,3-O-Cyclohexylideneerythritol Monoacetate from 2,3-O-Cyclohexylideneerythritol

Pseudomonas cepacia lipase catalyzed hydrolysis of 2, 3-O-cyclohexylideneerythritol diacetate in an emulsion of water and diisopropyl ether gives (2S,3R)-2, 3-O-cyclohexylideneerythritol monoacetate [(2S, 3R)-1-acetoxy-2,3-cyclohexylidenedioxy-4-hydroxybutane] with ≥ 99% ee in 91% yield by a preferential attack at the R-center CH₂OAc group. The enantiomeric (2R, 3S)-2,3-O-cyclohexylideneerythritol monoacetate is obtained by acetylation of 2,3-O-cyclohexylideneerythritol with vinyl acetate catalyzed by the same enzyme with ≥ 99% ee in 78% yield by a combined enantiotopos and enantiomer differentiation through a preferential attack at the R-center CH₂OH groups.