Synthesis of a tetrasaccharide repeating unit of the exopolysaccharide from Burkholderia multivorans

The chemical synthesis of a tetrasaccharide repeating unit of the exopolysaccharide discovered from Burkholderia multivorans with a 3-aminopropyl group linked to the glycan downstream end, α-D-Manp-(1→2)-α-D-Manp-(1→2)-3-O-methyl-α-D-Rhap-(1→3)-α-D-Rhap-O(CH₂)₃NH₂ (1), was described. The target tetrasaccharide was achieved by both a convergent [2 + 2] and a linear glycosylation strategies. The latter synthesis was proved to be more efficient than the former due to the excellent stereocontrol of glycosylation. Furthermore, the 3-aminopropyl group in the target molecule would enable its conjugation with functional biomolecules to explore its biological applications.