Preparation of (S)-2-, 3-, and 4-chlorostyrene oxides with the epoxide hydrolase from Sphingomonas sp. HXN-200

Abstract

The epoxide hydrolase from Sphingomonas sp. HXN-200 catalyzed the enantioselective hydrolysis of racemic 2-, 3-, and 4-chlorostyrene oxides 1-3 to form the corresponding (R)-diols and gave the (S)-epoxides 1-3 in high ee. The reactions were examined with frozen/thawed cells as well as cell-free extracts of Sphingomonas sp. HXN-200 as catalysts in an aqueous, and a two-liquid phase system, respectively. Biotransformation in the two-liquid phase system containing n-hexane as an organic phase showed a higher enantioselectivity than that in the single aqueous phase, due to the reduced non-enzymatic hydrolysis. Hydrolysis of 60 mM 2-chlorostyrene oxide 1 gave 31.3% of (S)-2-chlorostyrene oxide 1 in 98.8% ee with an enantioselectivity factor (E) of 12; hydrolysis of 100 mM 4-chlorostyrene oxide 3 afforded 30.8% of (S)-4-chlorostyrene oxide 3 with 98.6% ee with an E-value of 11. The best results were obtained with the hydrolysis of 3-chlorostyrene oxide 2: biotransformation with 100 mM substrate gave 44.0% of (S)-3-chlorostyrene oxide 2 in 99.0% ee with an E-value of 41; such enantioselectivity is much higher than that of any other known epoxide hydrolases for this reaction; preparative biotransformation demonstrated the efficient synthesis of (S)-3-chlorostyrene oxide 2, an intermediate for the preparation of an IGF-1R kinase inhibitor BMS-536924, with 99.1% ee and 41% isolated yield. © 2008 Elsevier Ltd. All rights reserved.