跨四个单键的折线型体系(W型) "w"coupling 水及为 跨五个单键的折线型体系 Ja,b-0 Hz ab=7 其它体系的远程偶合 Delayed COSY 之中产 gof signals which are very JBCA,J-based Configuration Analysis 固相核磁共振新技术 ,固相核藏共振技术可以实现对固体天然产物样品 的直按测定，但是所需样品量要大，所以在天然产 he ster 物分析中较少使用。 26 6 6 231 跨四个单键的折线型体系(W型) Hb Ha Hb Ha Hb Ha O H X O H 跨五个单键的折线型体系 N H O2N Ha Hc O Hb H H O 232 Ha Cl Hb Ha Cl N Hb O O N Ha Cl Hb O N Ha Cl Hb N O 4 Ja,b = 0 Hz 4 Ja,b = 7 Hz "W" coupling 233 其它体系的远程偶合 X Ha X Ha H Hb O b X Ha O Hb X Hb O Ha 234 Delayed COSY Delayed COSY allows linking of signals which are very weakly coupled (down to 0.1 Hz) Journal of Ethnopharm. 1991, 32, 103-110. 235 JBCA, J-based Configuration Analysis • NMR is the most useful method to elucidate the structures of natural products with a molecualar weight over 1000 since these compounds can hardly be crytalized. Murata had developed the method called "JBCA, J-based Configuration Analysis" which can be used to determine the stereochemistry of asymmetric carbon atoms residing in acyclic structures of natural products. • Murata,M., Matsuoka, S., Matsumori, N., Paul, G. K. and Tachibana, K. J. Am. Chem. Soc.. 121, 870-871 (1999). • Matsumori, N., Kaneno, D., Murata, M., Nakamura, H. and Tachibana, K. J. Org. Chem. 64, 866-876 (1999). 236 固相核磁共振新技术 • 固相核磁共振技术可以实现对固体天然产物样品 的直接测定,但是所需样品量要大,所以在天然产 物分析中较少使用