The polymerization of 7-benzyl-N-carboxy-L-glutamate anhydride with initiators such as sodium hydroxide, sodium methoxide, sodium borohydride and triethylamine can lead to polypeptides of molecular weight over 500,000 (degree of polymerization > 2000). In the cases of the first three initiators the molecular weight is related to the anhydride-initiator ratio (A/I) but is always higher than calculated for a given A/I. With triethylamine initiation the molecular weight is essentially independent of the amount of initator over a twenty-fold range of A/I. Data are presented that show that increasing the anhydride concentration, or raising the temperature of polymerization, yields polymers of much lower molecular weight. The solvent in which the polymerization takes place also affects the molecular weight. Evidence is presented that the N-carboxy anhydride ring opens in two different ways in the presence of sodium methoxide. This may be an explanation of the obtaining of molecular weights higher than calculated from the A/I's.Since the original synthesis of ce-amino acid-Ncarboxy anhydrides3 these compounds have been used extensively for the preparation of poly-'amino acids.4 Water, alcohols and amines can serve as initiators or catalysts for the polymerization of N-carboxy-a-amino acid anhydrides, and most previous work has been performed using such materials as initiators. There are only a few studies on the molecular weights of the polypeptides obtained and few data, except the work of Stahmann,6 on the effect of varying initiator concentration upon the molecular weight. Furthermore, there is no evidence that very high molecular weight polypeptides (molecular weight >100,000) could be prepared by the aforementioned means.

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