Department of Chemistry, University of California, Riverside, California 92521, USA.
J Phys Chem B. 2009 Aug 27;113(34):11696-701. doi: 10.1021/jp906538g.
While cinchona alkaloids play a key role in many applications, from medicine to catalysis, there is not yet a complete understanding of the reasons for their unique chemical behavior. Past studies have identified the chiral pocket formed by the two main constituting moieties of the cinchona, the quinoline and quinuclidine rings, as the main factor determining their physiological and enatioselective reactivity. That explanation, however, does not account for the differences observed among similar cinchona alkaloids. Here we show that subtle changes in the position of the substituent groups outside the central chiral pocket explain the disparities observed in basic physicochemical properties between pairs of near-enantiomers (quinine vs quinidine, cinchonidine vs cinchonine) such as crystal structure, solubility, and adsorption equilibrium. Both energetic and entropic factors need to be considered to fully account for the trends observed.
虽然金鸡纳生物碱在从医学到催化等许多应用中都起着关键作用，但人们对其独特化学行为的原因还没有完全了解。过去的研究已经确定了由金鸡纳的两个主要组成部分——喹啉环和奎宁环——形成的手性口袋是决定其生理和对映选择性反应性的主要因素。然而，这种解释并不能说明在类似的金鸡纳生物碱中观察到的差异。在这里，我们表明，在手性口袋外的取代基位置的微小变化可以解释在基本物理化学性质上观察到的两对近对映异构体（奎宁对奎尼定，辛可宁对辛可宁）之间的差异，如晶体结构、溶解度和吸附平衡。为了充分解释观察到的趋势，需要考虑能量和熵因素。
