Laboratory of Organic Chemistry

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Biologically active natural products have been regarded as the promising drug candidates and useful tool for life science.  Particularly, because of their potent biological activities, natural products isolated from marine organisms have attracted much attention of organic chemists, biologists, and pharmacologists. Since further biological studies are hampered by the limited availability from nature, chemical synthesis has been the sole realistic way to obtain sufficient amounts of the materials. Furthermore, due to their unique molecular architectures, these molecules are particularly attractive targets for synthetic chemists.

Since the discovery of brevetoxin B in 1981, a number of polycyclic ethers have been isolated from marine algae. These compounds show potent neurotoxicity by binding to the ion channels and cause massive fish kills and human food poisoning.  Moreover, the unusual ladder-shaped structures of these compounds are particularly attractive targets for synthetic chemists.  We have developed an efficient method for the convergent synthesis of polycyclic ethers via the intramolecular allylation and subsequent ring-closing metathesis. The methodology has beeb successfully applied to the total synthesis of marine natural products gambierol, brevetoxin B, and brevenal. Further studies towards the total synthses of marine polycyclic ethers are in progress.
Structural elucidation of natural products is not only fundamental but also significant research theme in natural product chemistry.  If the target molecule has a huge molecular size and a number of functional groups, the chemical synthesis is needed for the configurational assignment.   We have examined the synthetic approach toward the structural determination of the polyol natural product symbiodinolide.
We are also investigating the development of new synthetic methdology and its application to the total synthesis of natural products.  Selected examples of the target molecules are shown below.