Sequential polypeptides. Part III. The synthesis of two polyheptapeptides with functional side-chains

Abstract

Poly(leucylglutamyl-lysylalanylglutamylserylglycine)(I) and poly(leucylglutamyl-lysylalanylglutamylalanylglycine)(II) have been synthesised via the corresponding 1 -(biphenyl-4-yl)-1-methylethoxycarbonylheptapeptide acids which had their side-chains protected by t-butoxycarbonyl, t-butyl ester, and t-butyl ether groups. The C-terminal carboxy-group was activated with bis-4-nitrophenyl sulphite: selective acidolysis of the N(α)-protecting group followed by treatment with triethylamine in dimethyl sulphoxide gave a polymer which was deprived of its side-chain protecting groups by treatment with trifluoroacetic acid. After dialysis the weight average molecular weight of peptide (I) was found, by gel chromatography, to be 11,000 and that of peptide (II) to be 6000.