Visible‐Light‐Enabled Enantioconvergent Synthesis of α‐Amino Acid Derivatives via Synergistic Brønsted Acid/Photoredox Catalysis

An unprecedented radical cross‐coupling reaction was achieved between glycine esters and racemic α‐bromoketones catalyzed by synergistic Brønsted acid/photoredox catalysis, thus serving as an efficient platform for the synthesis of highly valuable enantioenriched unnatural α‐amino acid derivatives. This dual catalysis provides a powerful capability to control the reactive radical intermediate and iminium ion, thereby enabling enantioconvergent bond‐formation in a highly stereochemical manner. An array of valuable enantioenriched unnatural α‐amino acid derivatives bearing two contiguous stereogenic centers are readily accessible with high diastereoselectivity and excellent enantioselectivity, which include α‐amino acids with a unique β‐fluorinated quaternary stereocenter or its β‐all‐carbon counterpart. A strong chiral amplification effect was observed in this dual catalytic system. A radical addition reaction between glycine esters and racemic α‐bromoketones catalyzed by synergistic Brønsted acid/photoredox catalysis is presented. This dual catalysis controls the reactive radical intermediate and iminium ion to facilitate the bond‐forming event in a highly stereochemical manner. An array of valuable enantioenriched unnatural α‐AAs bearing two contiguous stereocenters are accessible.