Synthesis of Pseudomonas aeruginosa lipopolysaccharide core antigens containing 7-O-carbamoyl-l-glycero-α-d-manno-heptopyranosyl residues

The monosaccharide allyl 7-O-carbamoyl-l-glycero-α-d-manno-heptopyranoside, the reducing disaccharide 7-O-carbamoyl-l-glycero-α-d-manno-heptopyranosyl-(1→3)-l-glycero-d-manno-heptopyranose and the disaccharides allyl 7-O-carbamoyl-l-glycero-α-d-manno-heptopyranosyl-(1→3)-l-glycero-β- and α-d-manno-heptopyranoside were prepared in good yields. The 7-O-carbamoyl substituent was regioselectively introduced via NH3–NH4HCO3 treatment of a 6,7-O-carbonate group. Glycosylation steps were carried out using Me3SiOTf or BF3·Et2O promoted coupling of allyl alcohol with trichloroacetimidate or fluoride glycosyl donors, respectively. The deprotected allyl glycosides were reacted with cysteamine to afford spacer glycosides which were subsequently linked to bovine serum albumin. The artificial antigens which are related to the dephosphorylated heptose region of the lipopolysaccharide core region from Pseudomonas aeruginosa classified into RNA group I may be used for the characterization of monoclonal antibodies directed against inner core epitopes of human-pathogenic Pseudomonas species.