Synthesis of <scp>l</scp>-<i>glycero</i>- and <scp>d</scp>-<i>glycero</i>-<scp>d</scp>-<i>manno</i>-Heptose Building Blocks for Stereoselective Assembly of the Lipopolysaccharide Core Trisaccharide of <i>Vibrio parahemolyticus</i> O2

Abstract

Synthesis of bacterial cell surface l-<i>glycero</i>-d-<i>manno</i>-heptose (l,d-Hep)- and d-<i>glycero</i>-d-<i>manno</i>-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 α-l,d-Hep-(1→3)-α-d,d-Hep-(1→5)-α-Kdo core trisaccharide of the lipopolysaccharide of <i>Vibrio parahemolyticus</i> O2.