Synthesis, molecular dynamics simulations, and biology of a carba-analogue of the trisaccharide repeating unit of Streptococcus pneumoniae 19F capsular polysaccharide

The synthesis of a carba-analogue corresponding to the trisaccharide repeating unit of Streptococcus pneumoniae type 19F capsular polysaccharide, where a residue of carba-l-rhamnose has been inserted into the natural trisaccharide in place of l-rhamnose, is described. The conformational properties of the analogue were investigated with the aid of molecular dynamics simulations and were strictly analogous to those of the natural compound. The biological activity of the carba-analogue was comparable to that of the corresponding natural repeating unit, thus suggesting that this compound, more stable to hydrolysis, is a good mimic of the natural structure.