Oligomerization of a rhamnanic trisaccharide repeating unit of O-chain polysaccharides from phytopathogenic bacteria

An efficient synthesis of a protected trisaccharide building block α-l-Rha(1→3)-α-l-Rha(1→2)-α-l-Rha related to the structure of many lipopolysaccharide O-chains from phytopathogenic bacteria has been developed. The protecting group pattern consisting of benzoyl, benzyl and chloroacetyl groups facilitated the use of the trisaccharide building block in the synthesis of two higher oligomers, an oligorhamnosyl hexasaccharide and a nonasaccharide.