Li Minyi, Wu Jun, Zhang Si, Xiao Qiang, Li Qingxin
Guangdong Key Laboratory of Marine Materia Medica, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, P.R. China.
Magn Reson Chem. 2007 Aug;45(8):705-9. doi: 10.1002/mrc.2032.
Xylocarpins A and B, two new mexicanolides with a tiglate group at C-3, have been identified in the mixture using NMR spectroscopy. Both compounds were isolated in the mixture from the seeds of a Chinese mangrove Xylocarpus granatum. The first complete assignments of 1H and 13C NMR data for these mexicanolides were achieved by means of 2D NMR techniques, including 1H-1H COSY, HSQC, HMBC and NOESY spectra. In order to separate xylocarpins A (1) and B (2) by chemical method, the mixture of two compounds was reduced with sodium borohydride in anhydrous methanol. However, the reduction led to the opening of the delta-lactone ring in xylocarpin B and afforded compound 3 as the main product. The complete NMR assignments of compound 3 were also achieved by means of the above 2D NMR techniques. Moreover, xylocarpin A was easily transformed into xylocarpin B during our normal liquid column chromatography. From this point of view, xylocarpin A was deemed to be the genuine natural product and xylocarpin B might be an artifact.
已通过核磁共振光谱法在混合物中鉴定出木果内酯A和B，这两种新的墨西哥内酯在C-3位带有一个惕各酸酯基团。这两种化合物是从中国红树林植物木果楝的种子混合物中分离得到的。借助二维核磁共振技术，包括1H-1H COSY、HSQC、HMBC和NOESY谱，首次完成了这些墨西哥内酯的1H和13C核磁共振数据的归属。为了通过化学方法分离木果内酯A（1）和B（2），将两种化合物的混合物在无水甲醇中用硼氢化钠还原。然而，该还原反应导致木果内酯B中的δ-内酯环开环，并以化合物3作为主要产物。化合物3的完整核磁共振归属也通过上述二维核磁共振技术得以完成。此外，在常规液相柱色谱过程中，木果内酯A很容易转化为木果内酯B。从这一角度来看，木果内酯A被认为是真正的天然产物，而木果内酯B可能是一种人工产物。
