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.