Binding of Acetylcholine and Tetramethylammonium to Flexible Cyclophane Receptors: Improving on Binding Ability by Optimizing Host's Geometry
作者:Paolo Sarri、Francesca Venturi、Francesco Cuda、Stefano Roelens
DOI:10.1021/jo049899j
日期:2004.5.1
The structure of a cyclophanic tetraester (1), previously employed for investigations on the cation−π interaction, has been optimized to better accommodate acetylcholine (ACh) and tetramethylammonium (TMA) guests. Following indications from molecular modeling calculations, a flexible cyclophane receptor of significantly improved binding properties has been obtained by removing the four carbonyl groups
先前用于研究阳离子-π相互作用的环烷四酸酯(1)的结构已进行了优化,以更好地容纳乙酰胆碱(ACh)和四甲基铵(TMA)来宾。根据分子模型计算的指示,已经通过除去母体宿主的四个羰基获得了结合性能显着改善的柔性环烷受体。通过改进的方法制备了2,11,20,29-四氧合[3.3.3.3]对环磷烷(2),该步骤经便利地设计以避免形成引起严重分离问题的连续的环寡聚物。协会2与TMA苦味酸盐是在CDCl测量3在Ť = 296 K内由1个1 H NMR滴定并与结合为一组参考主机获得的数据,包括父四酯1,相应的cyclophanic四胺,的开链对应物2,其从cyclooligomers五聚体八聚体到。通过主体的几何优化,实现了从15倍(相对于四酯和四胺)到超过80倍(相对于开链四醚)的结合增强。对于各种抗衡离子,研究了2与ACh和TMA的结合。恒定的结合近8千焦mol的自由能的增量- 1相对于1观察到,与