Dual-function enzyme catalysis for enantioselective carbon-nitrogen bond formation

A haem protein that serves as a dual-function catalyst capable of inserting a carbene into a N-H bond to form alpha-amino lactones has been reported. The enzyme catalyses both carbene transfer and the subsequent proton transfer in a single active site. This transformation can proceed at the gram scale with high efficiency and enantioselective control. Chiral amines can be made by insertion of a carbene into an N-H bond using two-catalyst systems that combine a transition metal-based carbene-transfer catalyst and a chiral proton-transfer catalyst to enforce stereocontrol. Haem proteins can effect carbene N-H insertion, but asymmetric protonation in an active site replete with proton sources is challenging. Here we describe engineered cytochrome P450 enzymes that catalyse carbene N-H insertion to prepare biologically relevant alpha-amino lactones with high activity and enantioselectivity (up to 32,100 total turnovers, >99% yield and 98% e.e.). These enzymes serve as dual-function catalysts, inducing carbene transfer and promoting the subsequent proton transfer with excellent stereoselectivity in a single active site. Computational studies uncover the detailed mechanism of this new-to-nature enzymatic reaction and explain how active-site residues accelerate this transformation and provide stereocontrol.

Automated summary

A haem protein has been reported as a dual-function catalyst for inserting a carbene into an N-H bond to form alpha-amino lactones. The engineered cytochrome P450 enzymes demonstrate high activity and enantioselectivity in this enzymatic reaction. Computational studies provide insight into the detailed mechanism and stereocontrol of this new-to-nature reaction.