PREPARATION AND REACTIONS OF GLYCOSYL FLUORIDES: I. OLIGOSACCHARIDE SYNTHESIS: SYNTHESIS OF A HEXASACCHARIDE AND TOTAL SYNTHESIS OF THE RHYNCHOSPOROSIDES; II. A NOVEL APPROACH TO THE SYNTHESIS OF 2-DEOXY GLYCOSIDES.

摘要

The synthesis of carbohydrate-containing natural products is a significant goal in organic chemistry. An important problem in carbohydrate chemistry is the efficient, stereoselective formation of the O-glycosidic linkage. We have utilized glycosyl fluorides as intermediates to attain highly efficient synthesis of these important molecules.;The introduction to chapter II reviews the approaches to the construction of the 2-deoxy O-glycosidic linkage that have been previously reported in the literature; additionally, the novel 1,2-migration reaction, that was developed in these laboratories, is surveyed. The results and discussion section discusses new methodology for the preparation of 2-deoxy glycosides utilizing the 1,2-migration reaction. This approach was found to be highly effective for the synthesis of both (alpha)- and (beta)-2-deoxy glycosidic linkages.;The introduction to chapter I reviews the previously reported methodologies for the preparation of the O-glycosidic linkage and the chemistry of glycosyl fluorides. The previous biological and synthetic investigations of the rhynchosporosides are also presented. The results and discussion section of chapter I discusses the technology that has been developed in these laboratories for the synthesis of oligosaccharides employing glycosyl fluorides. The synthesis of a hexasaccharide and a series of phytotoxic oligosaccharides, the rhynchosporosides, is presented. The latter is the first oligosaccharide, natural product total synthesis utilizing solely glycosyl fluorides as the glycosyl donors. These methods were found to be highly effective for the synthesis of these oligosaccharides.