软珊瑚群柱虫中Clavutriolin衍生物的晶体结构和绝对构型的测定

软珊瑚群柱虫中的一个化学组分Ia,经乙酰化分离得到其衍生物Ib,用x射线晶体结构分析法测定Ib的晶体结构。Ib属正交晶系,空间群P2_12_12_1,a=12.722(2),b=14.726(4),c=12.255(3),z=4。由Ib的晶体结构分析结果推断Ia的分子式为C_(20)H-(33)O_4Cl。它是一个具有五、十一员双环碳骨架的新型含氯二萜。十一员环上带有一个环氧基和一个环外双键,分子中含有两个叔羟基和一个伯羟基。利用C1、O和C对Cukα辐射的反常散射,测定对于对映体敏感的Friedel反射对的Bijvoet差,确定了Ib的绝对构型,进而确定Ia的绝对构型。

CRYSTAL STRUCTURE AND ABSOLUTE CONFIGURATION OF CLAVUTRIOLIN DERIVATIVE FROM SOFT CORAL

Clavutriolin Ia, one of the chemical components of soft coral (Clavularia sp.), was isolated by its acetylated into Ib. The crystal structure has been determined by X-ray crystal structure analysis, The crystals are orthorhombic, space group P212121, with a = 12.722(2) , b = 14.726(4), c = 12.255(3)A, z = 4. The X-ray intensity data were collected on a four-circle diffractomer, using MoKα radiation. The crystal structure was solved by direct method and refined by block-diagonal least-squares method. The final R-factor was 0.0516 for 2985 observed independent reflections. The molecular structure of Ia, which was deduced from the result of crystal structure analysis of Ib, shows that it is a novel diterpene containing chlorine with a 5,11-bicyclic carbon skeleton, the molecular formula C20H33O4Cl. An epoxide group and an out-ring double-bond are attached to the 11-membered ring. The molecule contains one primary and two tertiary hydroxyl groups. The absolute configuration of Ib has been dete-rmined from the enantiomer-sensitive Bijvoet differences, using the CuKαanomalous scattering of Cl, O and C atoms. Ia can be assigned the same configuration as Ib.