Late-Stage <i>N</i>-Arylation of Tryptophan-Containing Peptides and Drug Molecules via Arylthianthrenium Salts

We report herein a mild and efficient method for the late-stage <i>N</i>-arylation of tryptophan and tryptophan-containing peptides using readily accessible arylthianthrenium salts through dual photoredox/copper catalysis. Applying this protocol, a library of noncanonical amino acids and <i>N</i>-arylated peptides was facilely prepared. Moreover, this protocol enables efficient peptide ligation and conjugation, offering convenient access to ligated peptides and peptide/drug conjugates. Remarkably, this strategy can also be applied for the late-stage modification of complex drug molecules.