Synthesis and NMR spectroscopic investigation of oligosaccharides containing Kdo and L-glycero-D-manno-heptopyranosyl residues.

The disaccharides O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->8)-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (8), O-L-glycero-alpha-D-manno-heptopyranosyl-(1-->7)-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (12), and O-alpha-D-mannopyranosyl-(1-->7)-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (21) and the branched trisaccharides O-L-glycero-alpha-D-manno-heptopyranosyl-(1-->7)-[O-(sodium 3-deoxy-alpha- and -beta-D-manno-2-octulopyranosylonate)-(2-->8)]-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (15 and 16) and O-alpha-D-mannopyranosyl-(1-->7)-[O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->8)]-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (24) were prepared. Per-O-acetylated mannopyranosyl or Kdo bromide derivatives were employed for the glycosylation steps under Helferich conditions, whereas the imidate derivative 9 was used for the coupling of the L-glycero-D-manno-heptopyranosyl residues. The oligosaccharides were fully characterized by NMR spectroscopic data. Their structures correspond to an artificial linkage pattern providing a potential cross-reactive epitope for antibodies directed against the inner-core-region of enterobacterial as well as chlamydial lipopolysaccharides.