School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
J Org Chem. 2013 Mar 15;78(6):2248-55. doi: 10.1021/jo302705k. Epub 2013 Jan 22.
Oligomers of the achiral amino acid Aib adopt helical conformations in which the screw-sense may be controlled by a single N-terminal residue. Using crystallographic and NMR techniques, we show that the left- or right-handed sense of helical induction arises from the nature of the β-turn at the N terminus: the tertiary amino acid L-Val induces a left-handed type II β-turn in both the solid state and in solution, while the corresponding quaternary amino acid L-α-methylvaline induces a right-handed type III β-turn.
非手性氨基酸 Aib 的低聚物在螺旋构象中，螺旋的手性可以由单个 N 端残基控制。我们使用晶体学和 NMR 技术表明，螺旋诱导的左右手性源于 N 端的β-转角的性质：三级氨基酸 L-Val 在固态和溶液中均诱导出左手型 II 型β-转角，而相应的四级氨基酸 L-α-甲基缬氨酸则诱导出右手型 III 型β-转角。
