Photoredox-catalyzed synthesis of α-alkylated unnatural amino acid derivatives with glyoxylimines and 4-alkyl-1,4-dihydropyridines

A visible-light-mediated radical alkylation of glyoxylimines with 4-alkyl-1,4-dihydropyridines as radical precursors has been developed. Iridium complex was selected as photocatalyst and also, Brønsted acid especially PhCOOH evidently improved the reactivity. A variety of α-alkylated unnatural amino acid derivatives could be produced in good yields. In addition, the straightforward and efficient one-pot procotol, involved a multicomponent reaction of ethyl glyoxalate, primary amines and 4-alkyl-1,4-dihydropyridines occurred smoothly to enable facile access to unnatural amino acid derivatives.