A New Method of Reducing Nitroarginine-peptide into Arginine-peptide, with Reference to the Synthesis of Poly-l-arginine Hydrochloride

With stannous chloride in formic acid, nitroarginine can be reduced to l-arginine hydrochloride quantitatively. This new method for the removal of the nitro group was applied successfully in the synthesis of poly-l-arginine hydrochloride from poly-l-nitroarginine, which had been prepared by the polymerization of N-carbothiophenyl-l-nitroarginine in dimethylsulfoxide at 120°C for 14 hr. The infrared absorption spectra of these polymers showed absorptions at 1708 cm−1 and 1766 cm−1, these absorptions might correspond to the C=O group in the hydantoin of the N-terminal. The poly-l-arginine hydrochloride showed positive Biuret and Sakaguchi reactions.