Synthesis of L-glycero- and D-glycero-D-manno-Heptose Building Blocks for Stereoselective Assembly of the Lipopolysaccharide Core Trisaccharide of Vibrio parahemolyticus O2

Synthesis of bacterial cell surface L-glycero-D-manno-heptose (L,D-Hep)- and D-glycero-D-manno-heptose (D,D-Hep)containing higher carbon sugars is a challenging task. Here, we report a convenient and efficient approach for the synthesis of the L,D-Hep and D,D-Hep building blocks. Using L-lyxose and D-ribose as starting materials, this approach features diastereoselective Mukaiyama-type aldol reactions as the key steps. On the basis of the synthetic L,D-Hep and D,D-Hep building blocks, we achieved the first stereoselective synthesis of the unique alpha-L,D-Hep-(1.3)-alpha-D,D-Hep-(1 5)-alpha-Kdo core trisaccharide of the lipopolysaccharide of Vibrio parahemolyticus O2.