秋水仙碱立体异构体电子结构及圆二色谱性质的理论研究

摘要

The structures of four stereoisomers of colchicine have been studied by the theoretical calculations using density functional theory(DFT) and time-dependent density functional theory (TD-DFT)at B3LYP/6-311 ++G** level. Based on the optimized structures, the vibrational circular dichroism(VCD), ultraviolet-visible(UV-Vis) and electronic circular dichroism(ECD) spectra of every stereoisomer were investigated. In addition ,the influence of water solvent on the electronic structures and spectral properties were estimated for getting a deep insight into the nature of colchicine. The results demonstrate that the stability of stereoisomers decreases in the sequence: Ⅰ = Ⅲ ＞ Ⅱ = Ⅳ. There is a dihedral angle between ring A and B because of the strain of ring C. Ⅰ and Ⅱ (or Ⅲ and Ⅳ )are enantiomers, of which VCD and ECD spectra are mirror images of each other. The title compounds are more stable in water. The solvent also may make the absorption peak around 370 nm show a red shift.%采用量子化学密度泛函理论(DFT)在B3LYP/6-311++G二水平上对秋水仙碱四个立体异构体分子几何构型进行了优化,在优化的基础上进行了振动圆二色谱(VCD),紫外-可见光谱(UV-Vis)和电子圆二色谱(ECD)研究.为模拟真实条件,以水为溶剂,计算其对分子电子结构和光谱性质的影响.研究结果表明:秋水仙碱四个立体异构体均能稳定存在,其中异构体Ⅰ 、Ⅲ能量较低,为优势构型.由于分子中环C存在张力,造成环A与环B之间存在约500的二面角.立体异构体Ⅰ与Ⅲ、Ⅱ与Ⅳ分别为对映异构体,其VCD和ECD呈镜像关系.水溶液中,秋水仙碱分子更为稳定;水溶液还使秋水仙碱UV-Vis光谱370 nm左右的吸收峰发生红移.