Site‐Selective Functionalization of (sp3)C−H Bonds Catalyzed by Artificial Metalloenzymes Containing an Iridium‐Porphyrin Cofactor

• Published in: Angewandte Chemie (International ed.) 2019-09, Vol.58 (39), p.13954-13960
• Main Authors: Gu, Yang, Natoli, Sean N., Liu, Zhennan, Clark, Douglas S., Hartwig, John F.
• Format: Article
• Language: English
• Subjects: artificial metalloenzymes; biocatalysis; Carbenes; Catalysts; Chemical reactions; C−H functionalization; Hydrogen bonds; Iridium; Isomers; Mutants; P450 enzymes; porphyrins; Selectivity
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201907460

The selective functionalization of one C−H bond over others in nearly identical steric and electronic environments can facilitate the construction of complex molecules. We report site‐selective functionalizations of C−H bonds, differentiated solely by remote substituents, catalyzed by artificial metalloenzymes (ArMs) that are generated from the combination of an evolvable P450 scaffold and an iridium‐porphyrin cofactor. The generated systems catalyze the insertion of carbenes into the C−H bonds of a range of phthalan derivatives containing substituents that render the two methylene positions in each phthalan inequivalent. These reactions occur with site‐selectivity ratios of up to 17.8:1 and, in most cases, with pairs of enzyme mutants that preferentially form each of the two constitutional isomers. This study demonstrates the potential of abiotic reactions catalyzed by metalloenzymes to functionalize C−H bonds with site selectivity that is difficult to achieve with small‐molecule catalysts. Ir‐replaceable: Site‐selective functionalizations of C−H bonds differentiated solely by remote substituents were achieved with nearly 10:1 ratios between constitutional isomers by using two distinct mutants of an artificial metalloenzyme generated from an evolvable P450 scaffold and an Ir‐porphyrin cofactor. This site selectivity is difficult to achieve with small‐molecule catalysts.