Helical Secondary Structures of Oligopeptides Composed of CMral Five-membered Ming Amino Acids

摘要

Homopeptides composed of achiral cyclic amino acids form 3_(10)-helical structures, in which both right-handed and left-handed screw sense of helices exist [1]. We have reported that homo-chiral homopeptides composed of chiral cyclic amino acid (S,S)-Ac5c~(dOM) having side-chain chiral centers but not having α-carbon chiral centers, preferentially form left-handed (M) helical structures [2]. The left-handed helical-screw sense was exclusively controlled by the side chain chiral centers, without an a-carbon chiral center. Herein, we synthesized two diastereomeric five-membered ring a-amino acids (1S,3S)- and (1R,3S)-1-amino-3-(methoxy)cyclopentanecarboxylic acids (Ac5c~(O,)), prepared two series of Ac5c~(OM) homo-chiral homopeptides, and studied their preferred secondary structures [3].