Chemical synthesis of the tetrasaccharide repeating unit of the O-antigenic polysaccharide from Plesiomonas shigelloides strain AM36565

• Synthesis of a tetrasaccharide having one GlcpNAc and one GalpNAc unit each with efficient and stereoselective glycosylation reactions.
• Use of azido and N-phthalimido groups as acetamido precursors to achieve 1,2-cis and 1,2-trans glycosylation respectively.
• Use of H2SO4–silica in conjunction with N-iodosuccinimide for the activation of thioglycosides.

Chemical synthesis of the tetrasaccharide repeating unit of the O-antigenic polysaccharide from Plesiomonas shigelloides strain AM36565 is reported. Glycosylations between suitably protected monosaccharide synthons were achieved by the activation of thioglycosides in the presence of H2SO4–silica in conjunction with N-iodosuccinimide. The glycosylations accomplished were highly stereoselective and afforded the desired products in good to excellent yields.

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