Enantioselective hydrolysis of functionalized 2,2-disubstituted oxiranes with bacterial epoxide hydrolases

The biohydrolysis of 2,2-disubstituted oxiranes bearing various oxygen func tional groups was investigated using the epoxide hydrolase activity of 11 b acterial strains. The results show that the activity and the selectivity st rongly depend on the substrate structure and the biocatalyst. Whereas subst rates possessing free hydroxyl groups were not transformed, their analogs, protected as ethers, were well accepted. This allowed the convenient modula tion of the enantioselectivity by proper choice of the ether group accordin g to size and polarity. it was found that the distance of the ether-oxygen to the stereogenic quaternary carbon center of the oxirane ring had a profo und influence on the enantioselectivity, and several oxiranes were resolved with good to excellent selectivities. The enantiomerically enriched epoxid es and vicinal diols thus obtained contain a useful "synthetic handle" in t heir side chain, which allows their use as building blocks in asymmetric sy nthesis.