5-8-5員環系高級テルペノイドの全合成

抄録

Several higher terpenoids having 5-8-5-membered tricyclic frameworks have been isolated from various kind of natural sources. For the total synthesis of this class of compounds, it is desirable that the synthetic strategy has a stereochemical flexibility, since the stereochemistries involving a basic carbon skeleton are quite different depending on the origins. Our synthetic scheme involves three key-steps, which are the dimerization of two iridoids getting B-seco derivatives, the Cope rearrangement of the condensates controlling the stereochemistry of C-11, and the ring-closure forming the central 8-membered ring. We finally accomplished the method to control the transition states in the second step with which any stereochemical combinations of C-6, C-11, and C-14 can be constracted freely. The versatility of this synthetic methodology has been proved by the total syntheses of stereochemically different type of terpenoids, such as ceroplastol II, dictymal, cycloaraneosene, and the diterpene potion of plagiospirolide.