二维核磁共振波谱和分子力学方法计算香茶菜醛溶液中的三维空间结构

Determination of Three-Dimensional Structures of Amethystonal in Solution by 2D-NMR and Molecular Mechanics Calculation

采用二维核磁共振波谱完全归属了天然有机化合物香茶菜醛的~1H和^(13)C NMR化学位移,测定了部分质子的偶合常数,并用孤立自旋对近似方法定量处理香茶菜醛的相敏NOESY谱,根据1/r_(ij)~8∝A_(ij)计算出相应的质子间距离.其溶液中的三维空间结构采用以NMR结构参数为初始数据的WUPH计算程序和分子力学能量优化(MM2)完成计算.计算结果表明,得到的香茶菜醛在溶液中的三维空间结构反映了该化合物在溶液中的真实空间结构.

Amethystonal was an effectively antineoplastic, antiphlogistic and antibacterial component first isolated from the leaves of Rbdosia amethystoides(Beath) C. Y. WU et Hsuen. , a Chinese herbal medicine collected in Henan province of China. The 13C and 1H NMR spectra were comepletely assigned by decoupled 13C spectrum, DEPT, hetero- and homo-nuclear correlation spectra. The proton coupling constants were measured by resolution-enhanced ID-1H spectrum and 2D-J-resolved spectrum. The interproton distances between proton i and j were calculated according to 1/ij6∝, where Aij was the integration value of the cross peak in phase sensitive NOESY spectrum. The initial spatial structure of amethystonal in solution was computed by WUPH method with the structural parameters measured by NMR experiments as input data, and the minimized three dimensional structure was obtained through the molecular mechanics calculation on the basis of WUPH calculation. The interproton distances of each proton pairs obtained from the cross peaks in phase sensitive NOESY spectrum were calculated from the atomic coordinates, and the coupling constants of protons were predicted from the dihedral angles given by MM2 method with Karplus equation. The maximum deviation between interproton distances calculated with energy minimizing calculation and that obtained from NOESY experimental data of amethystonal was 0. 045 nm, and the root-mean-square deviation was 0. 023 nm. The analysis of interproton distances together with the analysis of coupling constants indicated that the com-binization of WUPH method based upon the NMR experimental data with the molecular mechanics (MM2) calculation could provide the three-dimensional structure of amethystonal in solution.