Direct photochemical trifluoromethylation of histidine-containing peptides

Abstract Photochemical trifluoromethylation of the imidazole ring of histidine in the tripeptide Glp-His-Pro-NH 2 (TRH) has been achieved to furnish a mixture of the isomers, 2- and 4(5)-CF3-Im-TRH, which have been separated by reverse-phase HPLC and characterized.