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应用规范不变原子轨道GIAO法在HF/6-31G水平计算了MM3、PM3和HF/STO-3G三种最优分子构型下紫杉醇的δ1H-NMR和δ13C-NMR.对NMR化学位移计算值与实验值的对比和误差的统计和分析表明,采用HF/STO-3G优化的几何构型计算得到的化学位移误差最小,因此这一构型与实际分子最为接近.从理论构型得到4-OAc与3’-H的距离为0.2663nm,4-OAc与3’-Ph的距离为0.3104nm,4-OAc与2-OCOPh的距离为0.3707nm,支持了Williams等关于紫杉醇分子内存在NOE(nuclearoverhausereffect)效应及Velde等关于在极性溶剂中4-OAc与3’-Ph、2-OCOPh形成分子内疏水簇的观点.
The δ1H-NMR and δ13C-NMR spectra of paclitaxel in the three optimal molecular configurations of MM3, PM3 and HF / STO-3G were calculated at the HF / 6-31G level using the canonical atomic orbital GIAO method. Compared with the experimental data, the statistics and analysis of the errors show that the chemical shift error calculated by HF / STO-3G optimized geometry is the smallest, so this configuration is the closest to the actual one.From the theoretical configuration, the 4- The distance between OAc and 3’-H is 0.2663nm, the distance between 4-OAc and 3’-Ph is 0.3104nm, the distance between 4-OAc and 2-OCOPh is 0.3707nm, nuclear overhause effect and Velde et al.’s opinion on the formation of intramolecular hydrophobic clusters between 4-OAc and 3’-Ph, 2-OCOPh in polar solvents.