Iron photocatalysis towards site-selective C(sp ³ )–H alkylation of glycines and peptides

)-H alkylation of glycines and peptides. The method exhibits broad applicability, cost-effectiveness, and excellent tolerance to various functional groups. It is a flexible and efficient approach applicable to the synthesis of various unnatural α-amino acids and enables peptide drug bioconjugation. In addition to secondary and tertiary radicals, the iron-LMCT system enables access to primary radicals and the highly unstable methyl radical, derived from acetic acid, facilitating the production of methylated glycine derivatives. Preliminary mechanistic studies suggest a reaction pathway involving an Fe(iii)-Fe(ii)-Fe(iii) redox cycle and radical-radical cross-coupling.