新香茶菜素的晶体结构和电子结构研究

Study on the Crystal Structure and Electronic Sturcture for Neorabdosin

新香茶菜素是从中草药显脉叶香茶菜中提取出来的一种天然有机二萜化合物．由 Ｘ 射线衍射测定结果可知，其晶体属单斜晶系，空间群为 Ｐ２１ ，α＝ ０ ．６７７６（２） ，ｂ ＝ １ ．４６４０（８） ，ｃ ＝ １ ．１４１２（５）ｎ ｍ ，β＝ ９５ ．７１°（３） ， Ｚ＝ ２ ．晶体结构表明，分子中含有一个α－ 亚甲基环戊基乙酸酯和一个四氢γ－ 吡喃酮结构，这两种结构中与环直接键连的双键部分具有一定的内应力，是反应活性区．由量子化学计算结果可知，该分子的 Ｈ Ｏ Ｍ Ｏ 主要是由α－ 亚甲基环戊基乙酸酯的 Ｃ＝ Ｃ 双键原子所组成， Ｌ Ｕ Ｍ Ｏ 主要是由四氢γ－ 吡喃酮的 Ｃ＝ Ｏ 双键原子所组成， Ｌ Ｕ Ｍ Ｏ 是一个π Ｍ Ｏ．

Neorabdosin is a kind of the natural diterpenoids extracted from rabdosia nervosin (a chinese medical herb). From the results of x ray diffraction determination, it is found that the crystal belongs to monoclinic system with the space group P2 1, a=0.6776(2),b= 1.4640(8) ,c=1.1412(5) nm ,β=95.71°(3),Z =2. In the molecular there is a 5 membered ring with the C=C bond in its outer side and a 6 memebered ring with the ether bound and C=O bond in its outer side. The C=C bond and C=O bond are active zone owing to its strain. From the results of the quantum chemical calculations it is found that the HOMO mainly consists of the above C=C bond atoms, the LUMO is a πMO, which mainly consists of the above C=O bond atoms.