Pyroglutamate PTMs as Bioorthogonal Reactive Handles: Ru/Ni Photoredox Coupling

Abstract Post‐translational modifications (PTMs) play essential roles in living systems. However, the biological roles of some PTMs, such as N‐terminal pyroglutamate, are poorly understood due to a dearth of chemical and/or biological tools to label, quantify, or identify pyroglutamate residues. In this report, we describe a photoredox catalysis process that enables direct pyroglutamate N–H arylation in peptides and proteins, using (hetero)aryl bromide reagents. The reactivity demonstrates the potential for multi‐point binding to recognize peptide backbone structures for exquisitely chemoselective modifications in complex polyfunctional environments. The results provide the first chemical tool to modify pyroglutamate residues within complex polypeptides in biocompatible aqueous environments.