A new monooxygenase from Herbaspirillum huttiense catalyzed highly enantioselective epoxidation of allylbenzenes and allylic alcohols†
Asymmetric epoxidation is a green route to enantiopure epoxides, but often suffers from low enantioselectivity toward unconjugated terminal alkenes. Mining of the NCBI non-redundant protein sequences with a reconstructed ancestral sequence based on six styrene monooxygenases identified a monooxygenase (HhMo) from Herbaspirillum huttiense with 29.6–32.3% sequence identity with styrene monooxygenases, which was previously annotated as an alanine phosphoribitol ligase. HhMo catalyzed the epoxidation of allylbenzenes with moderate to excellent enantioselectivity yielding the corresponding epoxides in up to 99% ee. The HhMo-catalyzed epoxidation could also achieve the kinetic resolution of racemic secondary allylic alcohols, yielding the corresponding epoxides with up to 50% yields, as well as excellent enantio- and diastereoselectivity (up to >99% ee and >99% de) within 20–60 min, making a greener strategy for the production of valuable enantiopure glycidol derivatives in the fine chemical and pharmaceutical industries.