Polypeptides. III. The Synthesis of High Molecular Weight Poly-γ-benzyl-L-glutamates¹

Abstract

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.

Structural Investigations of Fibers and Films of Poly(p-phenylene benzobisthiazole). Volume 1

“…When the (010),(T10), (110) triplet is tilted such that only the nonequatorial portion of the intensity falls within the aperture (see Figure 38) and the image is compared to a successive image for which the entire reflection contributes to the image, we find both to have uniform spatial distributions of intensity (see Figure 39).…”

“…*PBG is polymerized from an N-carboxy anhydride by primary anionic initiators to form samples with a narrow molecular weight distribution [110,111] in contrast to PBT. The average molecular weight is easily determined [112] from the intrinsic viscosity since the polymer does not protonate in solution.…”

Helix to coil transition in poly(γ-benzyl-L-glutamate)

“…7-Benzyl-L-glutamate N-carboxy anhydride (NCA) was synthesized from ~-benzyl-L-glutamate and phosgene according to Blout and Karlson (10).…”

Acid-triggered core cross-linked nanomicelles for targeted drug delivery and magnetic resonance imaging in liver cancer cells

“…30,31 The synthesis and purification of γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) followed the established methodology, and originated from L-glutamic acid (Sinopharm Chemical Reagent Co, Ltd, Shanghai, People's Republic of China). [32][33][34] Allyl-poly(ethylene glycol)-b-poly(γ-benzyl L-glutamate) (allyl-PEG-PBLG) was prepared using a standard NCA method. 35,36 The removal of the benzyl group in PBLG block was achieved using an acid deprotection method.…”