The synthesis of glycosphingolipids: I.~The synthesis of lactosylceramide and lactosylsphingenine and a short synthesis of triacetyl -D-Erythro -sphingosine. II.~The synthesis of the Le(x) family of glycosphingolipids

Glycosphingolipids are ambiphilic molecules usually found embedded on the surface of mammalian cells. These molecules are important to a variety of cell-surface interactions and certain glycosphingolipids may act as antigenic cell markers. Structurally glycosphingolipids consist of a carbohydrate unit linked to the fatty acid amide of a long chain hydoxylamine, commonly known as sphingosine, which anchors these molecules on the cell surface. Unfortunately, many important glycosphingolipids are relatively inaccessible from natural sources especially in homogeneous form. Therefore the chemical synthesis of these biomolecules would provide a homogeneous source of glycosphingolipids. A classic problem in glycosphingolipid syntheses is coupling the glycan unit to the ceramide unit in an efficient manner. In chapter one of this manuscript, a short enantioselective synthesis of (2S,3R,4E)-2-azido-3-O-tert-butyldimethylsilyl-4-octadecene-1,3-diol is described. This azido-sphingosine equivalent has been demonstrated to be an efficient glycosyl acceptor with various glycosyl fluorides. Chapter one also describes the synthesis of both lactosylceramide and lactosylsphingenine from a common intermediate. Chapter two describes the synthesis of the Le$\sp{\rm x}$ family of glycosphingolipids, a series of tumor associated antigens. The described chemical synthesis provides a source of these complex glycosphingolipids and therefore may help further insight into the significance of these biomolecules