Destabilization of the 3(10)-helix in peptides based on C(alpha)-tetrasubstituted alpha-amino acids by main-chain to side-chain hydrogen bonds

The conformational preferences of a novel C(alpha)-tetrasubstituted alpha-amino acid characterized by concomitant Ci(alpha) - Ci(alpha) cyclization and the presence of two ether oxygen atoms in the gamma-positions of the six-membered ring 1,3-dioxane system were investigated. The homooligopeptide series based on O,O-isopropylidene-alpha-hydroxymethylserine from dimer through pentamer was synthesized. It was found that the extent of regular 3(10)-helix formation in peptides increases as peptide main-chain length increases.