Chemoselective, Enzymatic C-H Bond Amination Catalyzed by a Cytochrome P450 Containing an Ir(Me)-PIX Cofactor
Cytochrome P450 enzymes have been engineered to catalyze abiological C-H bond amination reactions, but this abiological process is limited by the low chemoselectivity for the amination of C-H bonds over competing reduction of the substrate to a sulfonamide. Here we report that P450s derived from a thermophilic organism and containing an iridium porphyrin cofactor (Ir(Me)-PIX) in place of the heme catalyze C-H bond amination reactions with high chemoselectivity for intramolecular insertion of the resulting nitrenes into C-H bonds over reduction of the azide to the sulfonamide and with broader substrate scope than that of enzymes containing iron porphyrins. These insertions into C-H bonds occur in yields up to 98% and TON of ~300. In one case, the enantiomeric excess reaches 95:5 er, and the reactions can occur with divergent site selectivity. The chemoselectivity for C-H bond amination is greater than 20:1 in all cases. Variants of the Ir(Me)-PIX CYP119 displaying these properties were identified rapidly by evaluating Ir(Me)-PIX variants in cell lysates, rather than as purified enzymes, accelerating the catalyst optimization. This study sets the stage to discover suitable enzymes to catalyze challenging C-H amination reactions.
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