Regio- and Stereoselective Concurrent Oxidations with Whole Cell Biocatalyst: Simple and Green Syntheses of Enantiopure 1,2-Diols via Oxidative Kinetic Resolution

Abstract

A simple and green method for preparing several enantiopure 1,2-diols was developed, for the first time, via regio- and stereoselective concurrent oxidations of the racemates with microbial cells. Sphingomonas sp. HXN-200 was found to catalyze the regio- and stereoselective oxidations of 3-O-benzylglycerol 1 to the corresponding α-hydroxy aldehyde 5 and then to the α-hydroxy carboxylic acid 6. Concurrent biooxidations of racemic 3-O-benzylglycerol 1 with resting cells of Sphingomonas sp. HXN-200 gave (S)-1 in 99.2% enantiomeric excess (ee) and 32% yield. Similar biooxidations of racemic 1-(4-chlorophenyl)-1,2-ethanediol 2, 1-(4-methylphenyl)-1,2-ethanediol 3, and phenyl-1,2-ethanediol 4 gave (R)-2 in 98.4% ee and 48% yield, (R)-3 in 99.6% ee and 45% yield, and (R)-4 in 98.7% ee and 36% yield, respectively. These represent the best results known thus far for the enzymatic syntheses of the useful and valuable diols (S)-1 and (R)-2–4.