Sequential polypeptides. Part VII. The synthesis of poly-(L-glutaminyl-L-alanine), a model of the silks produced by sawflies of the family Argidae

Abstract

The synthesis of poly-(L-glutaminyl-L-alanine), which has the repeating sequence proposed for the silks produced by members of the sawfly family Argidae, is described. The o-hydroxyphenyl ester method was used, the synthesis being performed via the fully protected tetrapeptide derivative benzyloxycarbonyl-L-glutaminyl-L-alanyl-L-glutaminyl-L-alanine 2-benzyloxyphenyl ester. Exhaustive dialysis of the product gave the required polymer of weight average molecular weight 5000–10,000 judged on viscosity criteria. Poly-(γ-methyl-L-glutamyl-L-alanine) was similarly prepared. An N-t-butyl substituent was shown to be unsuitable for side-chain amide protec-tion, since this group survives an hour's exposure to liquid hydrogen fluoride in the presence of anisole.