SYNTHETIC STUDY ON ANTIFEEDANT OF INSECTS AND RELATED COMPOUNDS

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In the final year, the following researches were carried out.Synthetic study on azadirachtin : Azadirachtin belongs to a class of limonoid which shows antifeeding and growth-inhibitory activities to insects. Although many synthetic chemists have been trying to synthesize the molecule, no total synthesis was reported due to the very complicated structure. This year, we have found that intramolecular Diets-Alder reaction followed by decarboxylation-Claisen rearrangement proceeded efficiently to construct the five asymmetric centers on A-ring. After several steps, a model compound, which possessed a simple cyclopentane ring instead of tricyclic moiety, was prepared and radical cyclization was investigated. The reaction proceeded suite smoothly to form Bring. This approach enables the shorter and more efficient total synthesis than those reported by other groups.Anther compound : In addition to azadirachtin, velamone, which is expected to exhibit the insect antifeedant activity, was synthesized by employing a newly developed intramolecular decarboxylative Robinson annulation which enabled the construction of bicyclic system of the molecule.