Synthesis of a Hexasaccharide Repeating Unit from Bacillus anthracis Vegetative Cell Walls

The first synthesis of hexasaccharide 1 representing a repeat unit of a polysaccharide specific to the vegetative cell wall of Bacillus anthracis is reported. The synthetic hexasaccharide is equipped with an n-pentenyl handle at the reducing terminus to allow for further functionalization. Key transformations during the synthesis are the conversion of a glucose into a mannosazide residue, a (2+2) coupling, followed by double α-galactosylation to furnish the hexasaccharide, and global deprotection under Birch conditions.