Chemical synthesis of the rare D-Fuc3NAc containing tetrasaccharide repeating unit of the O-antigenic polysaccharide from E. coli O74.

Chemical synthesis of the tetrasaccharide repeating unit of the O -antigen from E. coli O74 is accomplished by a convergent [2 + 2] block synthesis strategy. The challenging rare D-Fuc3NAc has been prepared using DTBP and TIPST mediated deoxygenation reaction. Other monosaccharide synthons are prepared through rational protecting group manipulations and the stereoselective glycosylations are achieved either by the activation of thioglycoside or glycosyl trichloroacetimidate. The target tetrasaccharide is made in the form of its 2-aminoethyl glycoside to facilitate further glycoconjugate formation without affecting the anomeric stereochemistry. [Display omitted] • Total chemical synthesis of the tetrasaccharide repeating unit of the O-antigent from E. coli O74. • Synthesis of rare D-Fuc3NAc derivative and incorporation in oligosaccharide. • Deoxygenation reaction with DTBP and TIPST. • Potential vaccine designing. [ABSTRACT FROM AUTHOR]