Inai Yoshihito, Ishida Yuya, Tagawa Kenichi, Takasu Akinori, Hirabayashi Tadamichi
Department of Environmental Technology and Urban Planning, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
J Am Chem Soc. 2002 Mar 20;124(11):2466-73. doi: 10.1021/ja017126w.
Recently, a novel chiral intermolecular interaction was found in an N-deprotected achiral nonapeptide that undergoes the predominance of one-handed screw sense through the addition of chiral small carboxylic acid (Inai, Y.; Tagawa, K.; Takasu, A.; Hirabayashi, T.; Oshikawa, T.; Yamashita, M. J. Am. Chem. Soc. 2000, 122, 11731). We here clarify to what extent such noncovalent chiral domino effect affects the helical screw sense of an N-deprotected chiral peptide. Two chiral peptides consisting of C-terminal L-Leu (1) or L-Leu(2) (2) and the preceding achiral helical octapeptide segment were employed. NMR and IR spectroscopy, and energy calculation indicated that both peptides adopt a helical conformation in chloroform. Peptide 1 showed a small excess of a left-handed screw sense for the achiral helical octapeptide, but peptide 2 strongly preferred a right-handed screw sense. The addition of chiral Boc amino acid to a chloroform solution of peptide 1, depending on its chirality, underwent a unique helix-to-helix transition or led to remarkable stabilization of the original left-handed screw sense. Peptide 2 retained the original right-handed screw sense on addition of chiral Boc-amino acid, but its helical stability changed to some extent depending on its added chirality. Therefore, the importance of noncovalent domino effect for controlling the helical screw sense or helical stability of a chiral peptide has been demonstrated here for the first time. In addition, we here have presented a unique system that both N-terminal noncovalent and C-terminal covalent domino effects operate simultaneously on the helical screw sense of a single achiral segment and have compared both powers for inducing the screw sense bias.
最近，在一种N-脱保护的非手性九肽中发现了一种新型的手性分子间相互作用，通过添加手性小羧酸，该九肽呈现出单手螺旋方向占主导的现象（稻井洋；田川和夫；高须明；平林拓；押川彻；山下正。《美国化学会志》2000年，122卷，11731页）。我们在此阐明这种非共价手性多米诺效应在多大程度上影响N-脱保护手性肽的螺旋方向。使用了两种由C端L-亮氨酸（1）或L-亮氨酸（2）（2）以及前面的非手性螺旋八肽片段组成的手性肽。核磁共振和红外光谱以及能量计算表明，两种肽在氯仿中均采用螺旋构象。肽1中，非手性螺旋八肽的左旋螺旋方向略有过量，但肽2强烈倾向于右旋螺旋方向。根据手性Boc氨基酸的手性，将其添加到肽1的氯仿溶液中，会发生独特的螺旋间转变或导致原始左旋螺旋方向显著稳定。添加手性Boc氨基酸时，肽2保留了原始的右旋螺旋方向，但其螺旋稳定性根据添加的手性在一定程度上发生了变化。因此，首次在此证明了非共价多米诺效应对于控制手性肽的螺旋方向或螺旋稳定性的重要性。此外，我们在此展示了一个独特的体系，其中N端非共价和C端共价多米诺效应同时作用于单个非手性片段的螺旋方向，并比较了两者诱导螺旋方向偏差的能力。
