Microbial epoxide hydrolases

Chiral epoxides and 1,2-diols, which are central building blocks for the asymmetric synthesis of bioactive compounds, can be obtained by using enzymes, which catalyse the enantioselective hydrolysis of epoxides - epoxide hydrolases. These biocatalysts are more widely distributed in fungi and bacteria than previously expected, and sufficient sources from bacteria, such as Rhodococcus and Myobacterium sp., or fungi, for instance Aspergillus and Beauveria sp. have recently been identified. The reaction proceeds via an S(N)2-specific opening of the epoxide leading to the formation of the corresponding trans-configurated 1,2-diols. For the resolution of 2-monosubstituted epoxides and for 2,2-disubstituted substrates fungal cells and several bacteria, respectively, have been shown to possess excellent selectivities. In addition, the use of non-natural nucleophiles such as azide or amine provides access to chiral azido- and amino-alcohols. The synthetic potential of these enzymes is illustrated with recent examples of kinetic resolutions of epoxides from the literature.