Synthesis, Ion Complexation Study, and 3D‐Structural Analysis of Peptides Based on Crown‐Carrier, C α ‐Methyl‐ L ‐DOPA Amino Acids

Selected series of terminally protected model peptides to the hexamer level, based on four novel, crown‐ether containing C α ‐methyl‐ L ‐DOPA ( L ‐Mdp) amino acid residues, namely L ‐Mdp[15‐C‐5], L ‐Mdp[18‐C‐6], L ‐Mdp[benzo‐24‐C‐8] and L ‐Mdp[( S )‐Binol‐20‐C‐6], combined with either L ‐Ala or L ‐Ala/Aib or Gly/Aib, were synthesized by solution methods. An ESI‐MS analysis of their alkali metal cation complexation ability was carried out. Their FTIR absorption, 1 H NMR, ECD, and VCD spectroscopic properties suggest that all of these crowned amino acids are strong inducers of (left‐handed) β‐turns and 3 10 ‐helical structures.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)