LINEAR POLYPEPTIDES OF A KNOWN REPEATING SEQUENCE OF AMINO-ACIDS . SYNTHESIS OF POLY-(L-GLUTAMYL-L-GLUTAMYL-L-ALANYLGLYCYL,[1-14C]GLYCINE ETHYL ESTER

Selective removal of the o-nitrophenylsulphenyl protecting group from N-o-nitrophenylsulphenyl-γ-t-butyl-L-glutamyl-γ-t-butyl-L-glutamyl- L-alanylglycine pentachlorophenyl ester gave γ-t-butyl-L-glutamyl-γ- t-butyl-L-glutamyl-L-alanylglycine pentachlorophenyl ester hydrochloride. Polymerisation of this material on the partially blocked monomer [1- 14C]glycine ethyl ester hydrochloride, at a relatively high dilution, gave poly-(γ-t-butyl-L-glutamyl-γ-t-butyl-L-glutamyl-L- alanylglycyl)[1-14C] glycine ethyl ester. The t-butyl ester protective groups were removed to give the title compound. The majority of the radioactivity was incorporated into the polypeptide. Comparison of the number average molecular weights obtained by end group assay and calculated from osmometry, 2.6 × 105 and 2.3 × 105 respectively, indicates that the polypeptide is linear.