Synergistic Glycosylation as Key to the Chemical Synthesis of an Outer Core Octasaccharide of Helicobacter pylori

Helicobacter pylori, a widespread gastric bacterial pathogen that infects 90 % of the population in developing countries, causes chronic gastritis, peptic ulcers and gastric cancer. Battling H. pylori infection is a serious challenge due to the increased resistance to antibiotics and the lack of vaccines. The lipopolysaccharide covering the H. pylori cell-surface outer membrane is an attractive target for the development of a glycoconjugate vaccine. Here, we report a 3+5 convergent synthesis of an outer core octasaccharide of H. pylori employing just three orthogonally protected building blocks. A synergistic glycosylation strategy enables the creation of five pivotal 1,2-cis-α-glucosidic bonds consist of four types of linkages using just three monomers. This strategy can be expanded to many 1,2-cis-α-gluoside-containing oligosaccharides both in solution and solid phase.