Taibaihenryiin C的构型、构象及晶体结构

从太白山产的鄂西香茶菜中分离得到新骨架的二萜类化合物TaibaihenryiinC,对其进行X射线衍射晶体结构分析,确定其分子中各取代基的相对构型、环构象及晶体结构.研究表明,C-3位的羟基和C-11位的乙酰氧基以C-20位的甲基为参考均位于β位;分子中的A环为椅式构象,B,C环接近于船式构象,D环接近于信封式构象.特别是在D环中存在较大的扭转角,使D环中有内应力存在,这表明该化合物具有潜在的生理活性.TaibaihenryiinC的晶体结构属正交晶系,P2₁2₁2₁空间群,晶胞参数a=0.6162(1)nm,b=1.2730(1)nm,c=2.5193(3)nm,Z=4.在晶体中分子间通过C-3位的-OH氢与C-11位的乙酰氧基上的羰基氧形成分子间氢键,使分子在晶体中沿a轴呈螺旋结构排列.

Configuration, Conformation and Crystal Structure for Taibaihenryiin C

Relative configuration, conformation and crystal structure for Taibaihenryiin C(1) isolated from Isodon henryi was elucidated on the basis of the single-crystal X-ray diffraction analysis. The X-ray crystal structure showed that the hydroxyl at C-3 and the acetoxyl at C-11 were in the β-orientations, respectively, and ring A is in a chair conformation, rings B and C approximate in the boat conformations, ring D approximates an envelope conformation in compound 1, respectively. A bigger tensile force existing in ring D suggests that this compound is a potential bioactive diterpenoid. The crystal of compound 1 is in orthorhombic crystal system, space group P2₁2₁2₁, accurate lattice constants: a=0.616 2(1) nm, b=1.273 0(1) nm, and c=2.519 3(3) nm, Z=4. The molecules arrange in a screw structure along a axis in the crystal resulted from intermolecular hydrogen bonds through the hydrogen atom of the hydroxyl at C-3 to the oxygen atom of the acetoxyl at C-11.