Synthesis of the tetrasaccharide repeating unit of the O -glycan from the polar flagellum flagellin of Azospirillum brasilense Sp7

Application of a Janus aglycon with dual function in benzyl-free synthesis of spacer-armed oligosaccharide fragments of polysaccharides from rhizobacterium Azospirillum brasilense sp7

Both protective and pre-spacer features of 4-(2-chloroethoxy)phenyl (CEP) aglycon, which belong to the class of Janus aglycons, were engaged in a benzyl-free synthesis of oligosaccharide fragments of polysaccharides from rhizobacterium Azospirillum brasilense sp7. Introduction of α-1,4-linked L-fucose residue was performed using 3,4-di-O-benzoyl-2-O-triisopropylsilyl-α-L-fucopyranosyl N-phenyltrifluoroacetimidate in excellent stereoselectivity and high yields. The obtained deprotected di-, tri- and tetrasaccharides contain 4-(2-azidoethoxy)phenyl (AEP) spacer aglycon, which allows straightforward preparation of neoglycoconjugates that will be used for the study of the role of lipopolysaccharide of rhizobacterium A. brasilense sp7 in plant-microbe symbiosis. The intermediate protected oligosaccharide building blocks with cleavable CEP/AEP aglycons have a strong potential for further application in the synthesis of more complex oligosaccharides.

Convergent chemical synthesis of the pentasaccharide repeating unit of the O-antigen from E. coli O158

Synthesis of the pentasaccharide repeating unit of the O-antigen fromE. coliO158 through a convergent [3 + 2] strategy is reported.