Experimentally Facile Controlled Polymerization of N-Carboxyan hydrides (NCAs), Including O-Benzyl-L-threonine NCA

It is demonstrated here that three different alpha-amino N-carboxyanhydrides (NCAs), including for the first time O-benzyl-L-threonine NCA, can be polymerized in a controlled/"living" fashion without the need for transition metal catalysts or complex custom-made glassware. Homopolymerizations in tetrahydrofuran gave monomodal distributions, high conversions, predictable M-n values and displayed first-order kinetics. Chain extension experiments from poly(benzyl-L-threonine), using N,N-dimethylacetamide to avoid the formation of insoluble beta-sheets, was used to create a range of block copolypeptides of controlled structure. Monomodal molecular weight distributions are observed throughout and molecular weights agree well with predicted values, although polydispersities are generally higher than those observed using more experimentally challenging techniques. This method therefore represents a practical approach to the synthesis of well-defined polypeptides without the requirement for specialized glassware or glove-box techniques. (c) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2882-2891, 2009