Chemical Synthesis of Core Structures

This chapter covers significant contributions to the chemical synthesis of bacterial lipopolysaccharide (LPS) core structures that have been achieved within the last decade. A related review on the synthesis of core structures appeared in 1992. The material presented does not strictly follow the somewhat arbitrary division of the core region into Kdo (3-deoxy-d-manno-oct-2-ulosonic acid)-, heptose- and outer core region, since many oligosaccharides of impressive size have been made comprising almost the whole region from outer core to the lipid A domain. Starting in the early 1980s, chemical synthesis of LPS structures attracted organic chemists as one of the paramount challenges in the chemistry of natural products. This fact may be ascribed to the complexity of protecting-group strategies needed, which have to take into account the compatibility of numerous blocking groups, the presence of ester- and amide-linked fatty acid residues, glycosidic and ester-bound phosphate groups and the acid-sensitivity of the ketosidic bonds of Kdo residues.