AbstractsChemistry

This thesis deals with synthetic studies towards Quassinoids and some aspects of the Chemistry of unsaturated sugar. The thesis consists of two chapters. In chapter I, approaches towards the synthesis quassinoids in general bruceantin, in particular are presented, while chapter II contains the chemistry of unsaturated sugars. Each chapter is subdivided into three sections, comprising introduction, results and discussion and experiments, respectively. The introductory section of chapter I briefly covers the biological activity of quassinoids and synthetic strategies culminating in the synthesis of bruceantin. Quassinoids are a group of diterpenes isolated from the bitter principles of Simaronbaceae family. They have been shown to possess antitumour and many other medicinal properties. Bruceantin (1) is one of the most active member of the group and has been the subject of extensive synthetic and pharmacological investigations. We conducted model studies towards the construction of BCD rings of the Quassinoids and towards this end, envisaged a strategy in which an intramolecular hetero Diels - Alder reaction find the key step. After a retrosynthetic analysis, we selected 4-(2-methyl-2-cyclohexen-l-yl) butyraldehyde (42) as the starting material. Compounds 42, when subjected to tandem Knoevanegal - hetero Diels - Alder reaction, failed to give any cycloadduct, but furnished only a condensation products. Several attempts to prepare the cycloadduct 53 were not fruitful. In another approach, the BCD ring system was proposed to be synthesized by the nucleophilic ring opening of an appropriately substituted cyclopropane.%%%References p.177-184