Department of Chemistry, Mississippi State University, Mississippi, USA.
Chirality. 2012 Oct;24(10):854-9. doi: 10.1002/chir.22083. Epub 2012 Jul 10.
The chromatographic chiral resolution of two new series of racemic 4-substituted-1,4-dihydropyridine derivatives was studied on a commercial Chiralpak AD-H column. Analytes without 5,5-dimethyl substituents (1-15) are more efficiently resolved than analytes with 5,5-dimethyl groups (16-30). The AD-H column discriminated between enantiomers through both hydrogen bonding attractions and π-π interactions. This interpretation is in accord with plots of the logarithm of separation factors, log(α), versus σ (Hammett-Swain substituent parameter) and σ(+) (Brown substituent constant) plots. By elucidating the effects of the remote substituents on these chiral separations, it was shown that the influence of π-π interaction forces increase when steric bulk effects act to decrease the hydrogen bonding attractive forces on the AD-H column.
本文研究了两个新系列的外消旋 4-取代-1,4-二氢吡啶衍生物在 Chiralpak AD-H 柱上的色谱手性拆分。没有 5,5-二甲基取代基的分析物（1-15）比具有 5,5-二甲基取代基的分析物（16-30）更有效地被拆分。AD-H 柱通过氢键吸引和 π-π 相互作用来区分对映异构体。这一解释与分离因子的对数 log(α) 与 σ（Hammett-Swain 取代基参数）和 σ(+)（Brown 取代常数）的关系图一致。通过阐明远程取代基对这些手性分离的影响，表明当空间位阻效应降低 AD-H 柱上氢键吸引力时，π-π 相互作用力的影响增加。
