Kdo Glycosylations and their Application in the Oligosaccharides Synthesis

The nonmammalian 8-carbon saccharide 3-Deoxy-D-manno-oct-2-ulsonic acid (Kdo) is the structural unit of bacterial lipopolysaccharides (LPSs) and capsular polysaccharides. In the inner core region of LPSs, Kdo is present, and this region is structurally conserved. Being nonmammalian in origin, Kdos are effectively recognized by the machinery of the native and adaptive immune system. Therefore, the synthesis of new Kdo derivatives and neoglycoconjugates is highly important for the development of vaccines. This review highlights recent accomplishments related to α-glycosylations, β-glycosylations and C-glycosylations of Kdos and their application to the stereoselective synthesis of inner core oligosaccharides.