Abstract
This article reviews generally the synthetic studies on limonoids, a large group of natural products with highly oxidized cyclic terpenoid structures, and related compounds. Recent interest on insect antifeedant and growth disrupting activity of limonoid compounds, specially of azadirachtin (17), gave an impetus to the synthetic investigations : Due to the complex structural elements involved, total synthetic works are very limited, the achievement having been reported only one case for the synthesis of an intact-ring limonoid, azadiradione (6). The synthetic studies on 17 are also under way, which represent a formidable challenge because of its utmost structural complexity. As a prelude to the total synthesis or with the aim of biological studies, a number of investigations have been carried out on the syntheses of degraded limonoids, and compounds with partial structure units of limonoids, which are mostly their CDE-ring analogs. These studies in conjunction with the partial syntheses of other ring structures have brought much progress in the methods for the construction of the unique structural units involved in limonoids.
