The Synthesis of Poly-l-arginine Hydrobromide and Copolymers of l-Arginine and Other Amino Acids

Pure crystalline Nω,ω′-dicarbobenzyloxy-l-arginine N-carboxyanhydride hydrochloride was obtained from Nα,ω,ω′-tricarbobenzyloxy-l-arginine and thionyl chloride. It was polymerized to poly-Nω,ω′-dicarbobenzyloxy-l-arginine. This polymer was converted to poly-Nω-carbobenzyloxy-l-arginine by treating it with alcoholic potassium hydroxide; also, both carbobenzyloxy groups of the protected polymer were completely removed into poly-l-arginine by treating them with hydrogen bromide in glacial acetic acid. Several copolymers containing l-arginine residue were also prepared by the copolymerization of the above NCA and the NCAs of other amino acids, such as γ-benzyl-l-glutamate, l-alanine, and Nε-carbobenzyloxy-l-lysine.