The position of the dinitrophenyl group in im-dinitrophenylhistidine derivatives

Abstract

Reinvestigation of the ring-opening reaction of N-(2,4-dinitrophenyl)imidazole with benzyl chloroformate in ethyl acetate–aqueous sodium hydrogen carbonate has shown the product to be benzyl N-[cis-2-(2,4-dinitroanilino)vinyl]-N-formylcarbamate (2), which undergoes deformylation on further treatment with alkali. Spectroscopic examination of corresponding products obtained from the 2,4-dinitrophenyl derivatives of 4(5)-methylimidazole and N^α-benzyloxycarbonyl-L-histidine has proved that 2,4-dinitrophenylation of these compounds occurs exclusively at the less hindered heterocyclic nitrogen atom, giving 1-(2,4-dinitrophenyl)-4-methyl-imidazole (1) and N^α-benzyloxycarbonyl-N^τ-(2,4-dinitrophenyl)-L-histidine (8), respectively.