Post-synthetic functionalization of tryptophan protected peptide sequences through indole (C-2) photocatalytic alkylation.

We report a selective, mild, and efficient C-H functionalization of tryptophan and of tryptophan-containing peptides with activated α-bromo-carbonyl compounds under visible-light irradiation. The protocol is valued by the wide substrate scope and excellent tolerance of sensitive functional groups present in the amino acid side chains. The method can be successfully extended to access pharmaco-peptide conjugate scaffolds.