|This present thesis describes the synthesis of different O-antigen fragments of the Gram-negative bacteria Burkholderia anthina and Pseudomonas aeruginosa. First, a hexasaccharide was synthesized by modular design principle. Some 2,3-diazido-2,3-dideoxy-D-mannuronic acids were then prepared with different aglycons. Key compounds of the multi-step synthesis were different allo-configurated 2,3-anhydroglucosides. After the successful synthesis of several glycosyl acceptors and donors, the compounds were used for the preparation of the corresponding β-linked disaccharide.