Expedient Synthesis of the Tetrasaccharide Repeating Unit Corresponding to the Cell Wall O ‐Antigen of Proteus vulgaris O19 Strain

Synthesis of the aminosugars rich tetrasaccharide related to the cell wall O ‐antigen of Proteus vulgaris O19 strain has been achieved in good yield. Functional group directed stereoselective α‐ and β‐glycosylations were carried out satisfactorily. A rare deoxysugar, L‐fucosamine derivative, was prepared from L‐fucose. The α‐D‐galactosidic linkage and β‐glycosidic linkage of D‐glucosamine moiety were achieved by applying p ‐methoxybenzyl (PMB) and Picoloyl (Pico) groups influenced H ‐bond mediated aglycone delivery, respectively. Satisfactory yields with desired stereochemistry at the glycosidic bonds were achieved in the stereoselective glycosylation reactions.