Synthesis of a Structural Analogue of the Repeating Unit from Streptococcus pneumoniae 19F Capsular Polysaccharide Based on the Cross-Metathesis–Selenocyclization Reaction Sequence

Pseudo-oligosaccharides have attracted much interest as scaffolds for the synthesis of sugar mimics endowed with very similar biological properties but structurally and synthetically simpler than their natural counterparts. Herein, the synthesis of pseudo-oligosaccharides using the cross-metathesis reaction between distinct sugar-olefins followed by intramolecular selenocyclization of the obtained heterodimer as key steps is first investigated. This methodology has been then applied to the preparation of structural analogues of the trisaccharide repeating unit from Streptococcus pneumoniae 19F. The inhibition abilities of the synthetic molecules were evaluated by a competitive ELISA assay using a rabbit polyclonal anti-19F serum.