Synthesis of poly (γ-benzyl-L-glutamate) with well-defined terminal structures and its block polypeptides with alanine, leucine and phenylalanine

The ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) was initiated by n-hexylamine in N,N-dimethyformamide under normal pressure at 0 °C. The products were characterizated by gel permeation chromatography, matrix-assisted laser desorption/ionization time of flight mass spectroscopy (MALDI-TOF MS), nuclear magnetic resonance etc. MALDI-TOF MS gave direct evidence that the side reactions during the polymerization of BLG-NCA could be greatly reduced by decreasing the reaction temperature, e.g. from room temperature to 0 °C. As a result, over 90% of the products were amino-terminated poly(γ-benzyl-L-glutamate) (PBLG) with low polydispersity index when the polymerization was carried out at 0 °C, which could be used to re-initiate the polymerization of other NCAs. Then several well-defined PBLG-containing block copolypeptides were successfully synthesized in a convenient way. Copyright © 2012 Society of Chemical Industry