Late-Stage Modification of Peptides with Maleimides through Palladium-Catalyzed β‑C(sp³)–H Alkylation

Transition-metal-catalyzed C–H activation has proven to be a powerful tool for the late-stage modification of peptides. We herein report a method for site-selective alkylation of peptides with maleimides through Pd-catalyzed β-C(sp³)–H activation. In this protocol, the methionine residues within peptides serve as the directing groups, which circumvented the preinstallation and subsequent removal of the directing groups. This chemistry exhibited broad substrate scope and can be utilized for peptide ligation.