Synthesis of an L-quinovose-containing disaccharide.

The synthesis of a versatile L-rhamnose monosaccharide synthon is described. This synthon is used in the synthesis of a disaccharide containing the rare sugar, 6-deoxy-L-glucose, linked to the 3-C-hydroxymethyl group of methyl 2,3-O-isopropylidene 3-C-(hydroxymethyl)-beta-D-erythrofuranoside.

Immunochemical characterization of polyclonal and monoclonal Streptococcus group A antibodies by chemically defined glycoconjugates and synthetic oligosaccharides.

Synthetic oligosaccharides of increasing complexity that represent different epitopes of the Streptococcus Group A cell-wall polysaccharide were used as haptens and glycoconjugates of bovine serum albumin (BSA) and horse hemoglobin (HHb) to characterize polyclonal and monoclonal antibodies. Rabbits were immunized with the BSA glycoconjugates of a linear trisaccharide, branched trisaccharide, and branched pentasaccharide. The binding specificities of the polyclonal antisera were determined by a series of inhibition ELISA studies in which disaccharide through pentasaccharide haptens were used as inhibitors of antibody-glycoconjugate binding. Monoclonal antibodies derived from mice immunized with a killed bacterial vaccine were selected for their binding to native polysaccharide antigen coupled to BSA and the BSA glycoconjugates of the di- and linear tri-saccharides. Polyclonal antibodies were moderately specific for the oligosaccharide epitope of the immunizing glycoconjugate and only those antibodies raised to the branched pentasaccharide antigen showed cross-reaction with the bacterial antigen. The behaviour of selected monoclonal antibodies parallels the binding profile of polyclonal antibodies in that the two highest-titre antibodies were directed toward an epitope displayed by the branched pentasaccharide.

Convergent synthesis of higher-order oligosaccharides corresponding to the cell-wall polysaccharide of the beta-hemolytic Streptococci group A. A branched hexasaccharide hapten.

A convergent synthesis of a hexasaccharide corresponding to the cell-wall polysaccharide of the beta-hemolytic Streptococci Group A is described. The strategy relies on the preparation of a key branched trisaccharide unit alpha-L-Rhap-(1----2)-[beta-D-GlcpNAc-(1----3)]-alpha-L-Rhap which functions both as a glycosyl acceptor and donor. The hexasaccharide is obtained after only three glycosylation reactions. This fully functionalized unit can serve, in turn, as a glycosyl acceptor or donor for the synthesis of higher-order structures. Deprotection gives a hexasaccharide for use as a hapten in immunochemical studies. The characterization of all compounds by high resolution 1H- and 13C-n.m.r. spectroscopy is also described.

Synthesis and n.m.r. analysis of branched trisaccharide and pentasaccharide haptens of the beta-hemolytic streptococci group A and the preparation of synthetic antigens.

The synthesis of branched trisaccharide and pentasaccharide portions of the cell-wall polysaccharide of the beta-hemolytic Streptococci Group A is described. The key dissaccharide acceptors, allyl or 8-(methoxycarbonyl)ocytol 3-O-(3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-4-O -benzyl - alpha-L-rhamnopyranoside, in conjunction with a selectively blocked alpha-L-rhamnopyranosyl chloride under Koenigs-Knorr conditions, afforded the branched trisaccharides in 81 and 62% yield, respectively. Analogously, glycosylation of the 8-(methoxycarbonyl)octyl disaccharide with a protected beta-D-GlcpNAc-(1----3)-alpha-L-Rhap-(1----3)-alpha-L-Rhap chloride gave the pentasaccharide in 43% yield. The key disaccharide acceptors were obtained, in turn, from the allyl or 8-(methoxycarbonyl)octyl rhamnoside acceptors and 3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl chloride under Koenigs-Knorr conditions. The latter glycosyl donor has not been described previously. Removal of the protecting groups afforded the trisaccharide haptens as their 1-propyl and 8-(methoxycarbonyl)octyl glycosides and the pentasaccharide as its 8-(methoxycarbonyl)octyl glycoside. The compounds have been subjected to detailed analysis by two-dimensional n.m.r. methods. Preparation of the synthetic antigens followed coupling of the 8-(methoxycarbonyl)octyl glycosides to bovine serum albumin via the acyl azide intermediates.