Complete Structure Elucidation of Maitotoxin

Maitotoxin是迄今为止已知的非生物聚合物中毒性最大和最大的天然产物。尽管环体系中的大部分立体中心可以通过简单的NOE实验来确定，但由于非环部分，特别是C1-C14和C134-C142侧链中存在不对称中心，阻碍了完整的结构解析。本研究成功地阐明了总结构的核磁共振波谱结合立体选择性合成的碎片结构。在核磁共振分析中，我们着重于碳-质子耦合常数，它提供了重要的二面角的构象和构型分配的侧链。绝对的立体化学也已指定的所有可能的立体异构体的合成片段C，这是由高碘酸盐降解的maitotoxin。

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.