Selective modification of tryptophan in polypeptides via C–N coupling with azoles using in situ-generated iodine-based oxidants in aqueous media

-generated iodine-based oxidant. The protocol was successfully applied to the selective modification of tryptophan in nonprotected polypeptide bearing oxidatively sensitive residues in acidic aqueous media. The present method allows the attachment of reactive handles to polypeptides and the peptide stapling.