2D NMR方法研究抗癌药物冬凌草乙素的结构与谱线归属

Structure Elucidation and Spectral Assignments of Ponicidin by Two Dimensional Nuclear Magnetic Resonance Techniques

用异核化学位移相关谱、远程异核化学位移相关谱和同核化学位移相关谱等现代核磁共振技术对抗癌中草药冬凌草中分离出的抗癌、抗菌有效成分冬凌草乙素分子的^(13)C和~1H化学位移进行了完全归属,为冬凌草乙素分子溶液中的三维空间结构研究提供了可靠的结构参数。

The 13C and 1H chemical shifts of ponicidin, which is one of antineoplastic and antiseptic effective components isolated from Rabdosia rvbescens (Hemsl. ) Hara, were completely assigned by het-eronuclear chemical shift correlation spectroscopy, long-range heteronuclear chemical shift correlation spectroscopy (COLOC-S) and homonuclear chemical shift correlation spectroscopy. Since the BIRD and TANGO pulse sandwich in COLOC-S pulse sequence were used to suppress effectively the one-bond cross peaks and decouple the modulation of long-range cross peak intensities due to the one bond couplings, the most three-bond 13C-1H interaction in ponicidin were dectected simultaneously in one COLOC-S spectrum, and some four-bond cross peaks were also observed in the same spectrum. After carefully analyzing the 13C and 1H chemical shift data, the XHCR cross peaks at 3. 790/72. 06, 4.196/72. 98 and 5. 010/69. 79 ppm were deduced as the cross peaks of methylene carbon atoms directly bonded to oxygen, the long-range 13C--1H cross peaks in COLOC-S spectrum confirmed that the 13C resonance signals at 72. 06, 72. 98 and 69. 79 ppm were assigned to Cl, C6 and C14 methylene group, and the corresponding 1H chemical shifts were 3. 790, 4.196 and 5. 010 ppm, respectively. The chemical shift assignments of other 13C, 'H resonance signals were completed by combining the COLOC-S spectrum with hetero- and homo-nuclear correlation spectra. The 1H resonance signals of two methyl group geminated at C4 carbon atom were identified unequivocally with the cross peaks in NOESY spectrum. The results show that the 2D NMR methods are very useful for the structure elucidation and spectral assignments of natural organic compounds, and the reliable structure parameters could be provided for calculating the three dimensional structures of ponicidin in solution.