Synthesis of the termite defensive trinervitanes possessing the unique IN-OUT skeleton

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Several species of termite soldiers inhabiting in the tropics are known to secrete their defensive substances, from which a varieties of cyclic diterpenes were characterized by G.D.Prestwich and his co-workers. The diterpenes are composed of bicyclics known as 2, 3-dihydroxy secotrinervitane, tricyclics as exemplified by 2, 3-dihydroxytrinervitanes, and tetracyclics as typified by kempan. The plausible biogenesis of these skeletons are suggested to commence from geranylgeranyl-OPP to monocyclic neocembrene, well known as a trail pheromone of the termite workers. The six membered ring formation causes the construction of bicyclic secotrinervitane skeleton, which seems the common intermediate for the further cyclization to the trinervitane and kempane skeletons. Based on the biogenetical route, we have already achieved the synthesis of secotrinervitane type diterpene. By the aids of financial support of Grant-in-Aid for Scientific Research c, we have further continued the effects to explore the synthetic route to the trinervitane and kempane skeletons featuring the biogenesis and succeeded the construction of both skeletons from the secotrinervitane.