Synthesis of a tetrasaccharide of the genus-specific lipopolysaccharide epitope of Chlamydia.

Allyl 2-acetamido-2-deoxy-3,4-O-(1,1,3,3-tetraisopropyldisiloxan-1,3- diyl)-beta-D- glucopyranoside was coupled with methyl (4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosyl bromide)onate (1) to give a good yield of the alpha-(2----6)-linked disaccharide, isolated after deacetylation and regioselective conversion into the corresponding 7',8'-O-carbonyl or 7',8'-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl) derivatives, respectively. Subsequent glycosylation with 1 gave a high yield of the alpha- and beta-(2"----4')-linked trisaccharide derivatives 16 and 18, whereas block synthesis using the alpha-(2----8)-linked Kdo-disaccharide bromide derivative 19 afforded a low yield of the corresponding alpha- and beta-(2"----4')-linked tetrasaccharide derivatives 20 and 22. Removal of the protecting groups furnished the disaccharide allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2----6)-2-acetamido -2-deoxy- beta-D-glucopyranoside, the trisaccharide allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2----4)-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2----6)-2-acetamido -2-deoxy- beta-D-glucopyranoside, and the tetrasaccharide allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2----8)-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2----4)-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2----6)-2-acetamido -2-deoxy- beta-D-glucopyranoside in high yield. Copolymerization of the allyl glycosides with acrylamide gave artificial polyvalent haptens suitable for defining epitope specificities of monoclonal antibodies directed against Chlamydia lipopolysaccharides.