SYNTHETIC STUDY ON ANTIFEEDANT OF INSECTS AND RELATED COMPOUNDS

在最后一年，进行了以下研究。印楝素的合成研究：印楝素是一类对昆虫具有抗摄食和抑制生长活性的类柠檬素。虽然许多合成化学家一直在尝试合成该分子，但由于其结构非常复杂，尚未有完全合成的报道。今年，我们发现分子内的Diets-Alder反应和脱羧- claisen重排有效地构建了a环上的5个不对称中心。经过几个步骤，制备了一个具有简单环戊烷环而不是三环的模型化合物，并对其进行了自由基环化研究。反应进行得很顺利，形成了Bring。这种方法比其他研究小组报道的全合成时间更短，效率更高。另一化合物：除印楝素外，利用新开发的分子内脱羧罗宾逊环法合成了有望具有昆虫抗食性的velamone，使其分子双环体系得以构建。

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.