First synthesis of an α-D-Fucp3NAc containing oligosaccaride: a study on D-Fucp3Nac glycosylation

The trisaccharide repeating unit of the O-antigen of the lipopolysaccharide from Xanthomonas campestris pv. campestris 8004, a pathogen of cruciferous crops, presents some structural features that renders it a challenging synthetic target:  the presence of a β-d-rhamnosidic linkage, the steric crowd on a 1,2-cis-diglycosylated d-rhamnose, and finally the noncommercial availability of its monosaccharide constituents. The synthesis of this trisaccharide as methyl glycoside has been accomplished by exploiting a strategy whose key steps were the sequential β-d-rhamnosylation with a 2-O-benzylsulfonyl-N-phenyltrifluoroacetimidate donor, debenzylsulfonylation, and coupling with a d-Fucp3NAc thioglycoside donor