Synthesis of oligosaccharides related to the repeating unit of the capsular polysaccharide from Streptococcus pneumoniae type 37

A tetra- and a pentasaccharide were synthesized as analogues to the structure of the Streptococcus pneumoniae type 37 capsular polysaccharide, a homopolymer with a disaccharide-repeating unit of →3)[β-d-Glcp-(1→2)]-β-d-Glcp-(1→. Synthesis of the tetrasaccharide employed a β-(1→2)-diglycosylation of a β-(1→3)-linked disaccharide. Subsequently, the pentasaccharide was synthesized from a suitably protected tetrasaccharide derivative by a β-(1→3)-extension at O-3′. Steric crowding was found to be an important factor in the formation of the pentasaccharide.