Palladium-catalyzed regioselective C-5 arylation of protected L-histidine: microwave-assisted C-H activation adjacent to donor arm.

An efficient, microwave-assisted direct C-H arylation at the C-5 position of fully protected L-histidine has been achieved via a palladium-catalyzed transformation reaction. This highly regioselective reaction has been applied to synthesize a series of protected 5-aryl-L-histidines using aryl iodides as coupling partners, in good to excellent yields. The reaction is compatible with substrates possessing electron-donating or electron-withdrawing substituents and offers high reactive functional group tolerance.