Complete Structure Elucidation of Maitotoxin

毛霉毒素是迄今已知的非生物聚合物中毒性最强、体积最大的天然产物。尽管环系中的大部分立体中心是通过简单的NOE实验确定的，但非环部分，特别是C1-C14和C134-C142侧链中不对称中心的存在阻碍了完整的结构阐明。本研究成功地用核磁共振波谱和立体选择性合成碎片结构的方法阐明了总的结构。在核磁共振分析中，我们重点研究了碳质子共振常数，它为侧链的构象和构型分配提供了重要的二面角。片断C的所有可能的立体异构体的合成也被指定为绝对立体化学，片断C是由毛霉毒素的高碘酸盐降解产生的。

Maitotoxin is the most toxic and largest natural product among non-biopolymers known to date. Althought most of stereogenic centers in ring systems was assigned by simple NOE experiments, the complete structural elucidation was hampered by the presence of asymmetric centers in acyclic portions, particularly, C1-C14 and C134-C142 side chains. The present study has successfully elucidated the total sturcture by menas of NMR spectroscopy coupled with stereoselective synthesis of the fragmental structures. In the NMR analysis, we focused on the carbon-proton copling constants, which provided important dihedral angles for the conformational and configurational assignments of the side chains. The absolute stereochemistry has been also assigned by the synthesis of all the possible stereoisomer for fragment C,which was generated by periodate degradation of maitotoxin.