定义Definition
阻转异构体是由于单键旋转受到严重空间位阻、能垒足够高而能够分离的构象异构体。最典型的是邻位有大取代基的联芳烃，它们具有轴手性。
Atropisomers are conformers separable because rotation about a single bond is so hindered that the barrier is high. The classic cases are biaryls with bulky ortho substituents, which possess axial chirality.
判据Criterion
大木道则（Ōki）给出的经验定义：室温下异构体半衰期至少 1000 秒（约 16.7 分钟），对应旋转能垒约 93 kJ/mol 以上。药物研发中常按能垒把阻转异构分为三类（< 84、84–117、> 117 kJ/mol）。
Ōki’s working definition: a half-life of at least 1000 s at room temperature, corresponding to a barrier above ~93 kJ/mol. Drug discovery classifies atropisomers by barrier (< 84, 84–117, > 117 kJ/mol).
例子Examples
6,6′-二硝基联苯-2,2′-二甲酸（1922 年克里斯蒂与肯纳首次拆分）；BINOL 与 BINAP 是不对称催化中最重要的阻转异构配体；万古霉素、某些激酶抑制剂含阻转异构轴。
6,6′-Dinitrobiphenyl-2,2′-dicarboxylic acid (first resolved by Christie and Kenner in 1922); BINOL and BINAP are key atropisomeric ligands in asymmetric catalysis; vancomycin and some kinase inhibitors contain atropisomeric axes.
命名Naming
轴手性用 Rₐ/Sₐ 或 P/M（螺旋方向）表示。
Axial chirality is labelled Ra/Sa or P/M (helicity).
年表Timeline
- 1922
克里斯蒂与肯纳拆分取代联苯
Christie and Kenner resolve a substituted biphenyl
- 1933
库恩提出 atropisomer 一词
Kuhn coins the term atropisomer
- 1980
野依等合成 BINAP
Noyori and co-workers synthesise BINAP