Synthesis of two sequential polypeptides by dispersion in benzene and their circular dichroism spectra in aqueous solution: Poly( L ‐Glu‐ L ‐Lys‐ L ‐Ala‐Gly) and Poly( L ‐Ala‐ D ‐Glu‐ L ‐Lys‐ D ‐Ala‐Gly)

The monomers γ‐benzylglutamyl‐ε‐benzyloxycarbonyl‐lysylalanylglycine pentachlorophenyl ester and alanyl‐γ‐benzyl‐D‐glutamyl‐ε‐benzyloxycarbonyllysyl‐D‐alanyl‐glycine pentachlorophenyl ester, were polymerized in dilute solutions of dimethylform‐amide (DMF) or as dispersions in the same volume of benzene. After deprotection with hydrogen bromide, the products were either chromatographed on Sephadex G‐50 or dialyzed. The polymers derived from the polymerization in benzene were considerably larger than those from DMF. The results in benzene indicated that high monomer to solvent ratios are not necessary for the production of high‐molecular‐weight sequential polypeptides. Circular dichroism spectra of the polymers and monomers at neutral and acid pH indicated that poly(L‐Glu‐L‐Lys‐L‐Ala‐Gly) exists in a random coil configuration and poly(L‐Ala‐D‐Glu‐L‐Lys‐D‐Ala‐Gly) exists in a β conformation.