| Research Abstract |
1) The first total synthesis of (+)-obtusenyne isolated from a red alga, Laurencia obtusa, has been achieved. Furthermore, two isomers of obtusenyne, which had been isolated by None and undetermined stereochemically, were totally synthesized. These results led to establishment of the absolute configuration of these compounds.
2) The synthetic route has been established toward realization of the proposed biosynthetic pathway for condensed cyclic polyether compounds of marine sources. Eventually, construction of the condensed bicyclic and tricyclic ether compounds were carried out firstly in endo-fashions starting from the corresponding polyepoxy alcohols as the models.
3) Two new efficient methods have been established in order to construct convergently two-condensed cyclic ethers.
4) The synthetic studies were developed toward the total synthesis of ciguatoxin which is the causative compound for ciguatera intoxication. The synthetic strategy was based on the convergent procedure to synthe
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size the four respective fragments and then to combine them constructing three residual 6-7-membered cyclic ether systems (CD,GH,JK). The synthesis of the CD and JK ring systems has been already achieved.
5) The first total synthesis of polycavernoside A isolated from a red alga, Polycavernosa tsudai, regarding as a causative compound for human intoxication, has been achieved. Furthermore, the structure-biological activity relationship has been clarified.
6) The study toward the total synthesis of pinnatoxins causing shell-fish poisoning originated from Pinna attenuata has been developed. Resultingly, the 1-step construction of the common BCDEF-ring system has been achieved. Furthermore, the strategy for construction of the AG-ring system has been established using an intermolecular Diels-Alder reaction by the model experiments.
7) The study toward the total synthesis of pectenotoxins causing shell-fish poisoning originated from Patinopecten yessoensis has been developed. Resultingly, all the fragments were able to be constructed except the C30 position. Less
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