Synthesis of Copoly(amino acids) as Potential Biomaterials by Diphenyl Phosphoryl Azide

Abstract

A convenient chemical synthesis of copoly(amino acids) as potential biomaterials is described. Direct copolycondensations of α-amino acids using diphenyl phosphoryl azide (DPPA) as condensation agent were carried out in the presence of triethylamine (TEA) as a base. The amino acids used were β-benzyl-L-aspartate (Asp.Bz), γ-benzyl-L-glutamate (Glu.Bz), L-phenylalanine (Phe), and O-benzyl-L-tyrosine (Tyr.OBz). Copoly(amino acids) with weightaverage molecular weights up to 28,000 were obtained in reasonable yields. Bimodal molecular weight distribution was observed in all the cases. Both the overall yield of the product and the yield of high molecular weight fraction are influenced by [DPPA]/[Monomer] and [TEA]/[Monomer] ratios. No significant solvent effect was observed.