Synthesis of terpenoids having unique IN-OUT skeleton and Development of their biological properties

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By the financial support of grant-in-aid for scientific research (C), the research of following two topics were projected, 1) synthesis of trinervitanes ; 2) synthesis of verticillol. After numerous amounts of unsuccessful trials, the trinervitane skeleton was constructed by our original synthetic plan. That is, allyl chloride (1) of secotrinervitane skeleton was prepared by multi-step reactions. By the action of silver perchlorate, 1 was converted to trinervitane (2) in high yield. The newly formed double bond of 2 was exclusively tetrasubstituted. 2 is a geometrical isomer of defense substance of trinervitane (3) isolated from termite soldier. Strain energy of geometrical isomers estimated by MM2 calculation revealed that 2 is the most stable among the isomers. This evidence suggests that hydride transfer to the inner trisubstituted double bond is the essential process in the biosynthesis of natural trinervitane (3) from the hypothetical progenitor (4). The hydride transfer releases the strain energy caused by sp^2 bond. The present results concerning successful synthesis of trinervitane skeleton (4) and the information about the biogenesis of trinervitane are the first achievement.Synthetic study of verticillol lead to the construction of gamma-lactone (5) via the synthetic intermediate, cyanovertecillene. The overall yield of the intermediate is still low and further improvement of the reaction conditions is needed. Development of the biological properties of all the compounds obtained in the present study remains unsolved and is the subject of future investigation.