Syntheses and Circular Dichroism Studies of Oligopeptides Having Tri- or Tetra-l-prolyl Sequences

CD spectra of many oligopeptides having tri- or tetra-l-prolyl sequences showed that a penta- or hexapeptide having a tetra-l-prolyl sequence took poly(l-proline) II helix irrespective of amino acid residues at N- or C-terminal of a l-prolyl cluster and that as to a size of the cluster, tri-l-prolyl sequence was enough to form the helix, when glycine was used as substituent.