Synthesis of PSI Oligosaccharide for the Development of Total Synthetic Vaccine against .

causes serious nosocomial diarrhea in humans. In particular, ribotype 027 strain, which is more virulent in nature, is associated with higher mortality rates. To prevent disease caused by , capsular polysaccharides such as PSI, PSII, and PSIII from the outermost protective layer of bacterium are good targets in the development of vaccine against . In this study, we report for the first time an efficient synthesis of phosphorylated PSI oligosaccharide and its derivatives in various lengths. We have also developed a one-pot strategy for the synthesis of a pentasaccharide repeating unit and used this approach to successfully synthesize the protected pentasaccharides in the gram scale.