Synthesis of a tetrasaccharide containing Janus aglycone related to the terminal fragment of polysaccharides of mycobacteria

A convergent synthesis of arabinofuranose-based, α-(1→5), β-(1→2)-linked tetrasaccharide related to the terminal fragment of lipoarabinomannan and arabinogalactan of mycobacteria was carried out. The tetrasaccharide was synthesized as a glycoside with 4-(2-azidoethoxy)phenyl aglycone belonging to the class of Janus aglycones, which can serve as both a temporary protective group of the anomeric position of the carbohydrate residue and a (pre)spacer for the synthesis of neoglycoconjugates (NGCs) useful in the development of new diagnostic agents for tuberculosis. The key step is the formation of a 1,2-cis-glycosidic bond.