Synthesis of biologically active oligosaccharides of the Lewis b family and investigations towards the synthesis of glycoclusters

Abstract: The gastric pathogen Helicobacter pylori is a Gram negative bacterium which may cause diseases such as peptic ulceration and gastric adenocarcinoma. It colonises a host by attaching to the gastric epithelial cells, an attachment mediated by outer membrane proteins on the bacterial surface, e.g, the blood group antigen binding adhesin, BabA. This adhesin recognises and binds to specific carbohydrates, Lewis blood group antigens, on the epithelial cell walls.This thesis presents the synthesis of three oligosaccharides of the Lewis family. A new and improved block synthesis of a Leb hexasaccharide and synthesis of HSA-conjugates thereof are described. Also presented are the syntheses of a Leb pentasaccharide and a B-Leb heptasaccharide via linear routes. The latter strategy is designed to enable the synthesis of other Lewis blood group antigens by only minor changes in protection patterns.Investigations have been made towards finding a route for the synthesis of glycoclusters using of unprotected carbohydrates. The biologically active dendrimers will be used in examinations of binding to galectin-3, an important animal lectin abundant in nature.The thesis also includes an efficient synthesis of an oxazolidinone protected thioethyl LacNAc disaccharide, and its ability as a donor has been examined.