Synthesis of block copolypeptides by click chemistry

A novel synthetic methodology to diblock copolypeptides was developed by ring-opening polymerization (ROP) of N-carboxyanhydrides (NCAs) from alpha-omega-functionalized initiators combined with the Huisgen 1,3 dipolar cycloaddition (click chemistry). Poly(gamma-benzyl-L-glutamate) (PBLGlu) and poly(trifluoroacetyl-L-Lysine) (PTFALys) containing either an azide or an alkyne functional group in alpha-position were first synthesized by ROP of the corresponding NCA at room temperature in DMF as a solvent, using appropriate omega-amino-containing alpha-alkyne and a-azido difunctional initiators. The Copper(I) -catalyzed coupling reactions of alpha-azido-PBLGlu with the alpha-alkyne-PTFALys, on the one hand, and of the alpha-alkyne-PBLGlu with the alpha-azido-PTFALys, on the other hand were suitably accomplished in DMF. This afforded the targeted PBLGlu-b-PTFALys diblock copolypeptides pos- sessing a triazole group in between the two 1 blocks, as evidenced by SEC, IR, and NMR analysis. Block copolypeptides could be successfully purified by selective extraction with chloroform.