有机磷化合物的研究 72.含磷非对映异构体^3^1P NMR 结构效应的分子力学研究

本文通过两组含磷非对映异构体^3^1P NMR化学位移的测定和分子力学计算,观察到非对映异构体之间,分子力学计算的磷原子局部Van der Waals相互作用能( E~V~D~W~-~P)是影响其^3^1P NMR化学位移的主要因素,即E~V~D~W~-~P大的异构体,δ~3~1~P在低场,E~V~D~W~-~P小的,δ~3~1~P在高场.这一结果对利用非对映异构体中某核的NMR化学位移的实验测定,结合分子力学计算的该核的局部Van der Waals相互作用能, 建立一种简便的确定非对映异构体中未知不对称中心的绝对构型的新方法,具有一定的理论意义和实用价值

Studies on organophosphorus compounds.72.a molecular mechanics study of the structure effect of phosphorus-based diastereoisomers on the ^3^1P NMR chemical shift

The structural influence of two series of phosphorus-based diastereoisomers, e.g. a-aminobenzylphosphonates I and II (R = alkyl, Ph), on the 31P NMR chem. shift is evaluated by mol. mechanics calculation The results reveal that the intramol. local Van der Waals interaction energy of phosphorus atom (EVDW-P) calculated by MM2(85) program is the predominating factor governing the magnitude of the chem. shift of the phosphorus nucleus. The isomer, which has relative large EVDW-P value will show downfield 31P NMR chem. shift or vice versa. This empirical approach provides the experimental basis of a new and facile method for the elucidation of the absolute configuration of diastereoisomers with any asym. center. It has, therefore, significant theor. importance and potential practical value.