Synthesis of pentasaccharide core structures corresponding to the genus-specific lipopolysaccharide epitope of Chlamydia

Abstract

The trisaccharides allyl O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2 → 6)- O-2-acetamido-2-deoxy-β- d-glucopyranosyl-(1 → 6)-2-acetamido-2-deoxy-α- and -β- d-glucopyranoside ( 16a and 16b), the tetrasaccharides allyl O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2 → 4)- O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2 → 6)- O-2-acetamido-2-deoxy-β- d-glucopyranosyl-(1 → 6)-2-acetamido-2-deoxy-α- and -β- d-glucopyranoside ( 19a and 19b), and the pentasaccharides allyl O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2 → 8)- O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2 → 4)- O-(sodium 3-deoxy-α- d- manno-2-octulopyranosylonate)-(2 → 6)- O-2-acetaido-2-deoxy-β- d-glucopyranosyl-(1 → 6)-2-acetamido-2-deoxy-α- and -β- d-glucopyranoside ( 23a and 23b) were prepared. The glycosidic linkages were formed using 1,3,4,6-tetra- O-acetyl-2-chloroacetamido-2-deoxy-β- d-glucopyranose ( 6) and FeCl 3 as promoter as well as per- O-acetylated Kdo mono- and di-saccharide bromide derivatives ( 12 and 20) under Helferich conditions. The oligosaccharides, which correspond to dephosphorylated part-structures of enterobacterial and chlamydial lipopolysaccharides, were characterized by NMR spectroscopy as well as plasma desorption and matrix-assisted laser desorption mass spectrometry.