Sequential Polypeptides. The Steric Hindrance of L-Valine Residues in the Polycondensation of Peptide Active Esters

Five tripeptide N-hydroxysuccinimide esters with N-terminal L-valine, L-phenylalanine, and L-alanine were polymerized in N,N-dimethylformamide with a variety of concentration of the monomers. The yields and molecular weights of the resulting sequential polypeptides were then compared in order to demonstrate the presence of the steric hindrance of the L-valine residue in polycondensation. The results of the polycondensation and the conformational study of the resulting polypeptides suggest that the side chain of the L-valine residue at the N-terminal position of the monomers hinders the polycondensation of the monomers.