First synthesis of β-d-Galf-(1→3)-d-Galp—the repeating unit of the backbone structure of the O-antigenic polysaccharide present in the lipopolysaccharide (LPS) of the genus Klebsiella Original Research Article

β-d-Galactofuranosyl-(1→3)-d-galactopyranose (1), the repeating unit of the backbone structure of the O-antigenic polysaccharide present in the lipopolysaccharide (LPS) of the genus Klebsiella, has been efficiently synthesized using 1,2:5,6-di-O-isopropylidine-α-d-galactofuranose (3) as the glycosyl acceptor and 2,3,5,6-tetra-O-benzoyl-β-d-galactofuranosyl trichloroacetimidate (6) as the glycosyl donor with TMSOTf as catalyst by the well-known Schmidt glycosylation method. The preparation of 3 was improved by increasing the ratio of DMF to acetone and employing a solid-supported catalyst.