A practical route to 3,6-dideoxyhexoses

A De Novo Route to 3,6-Dideoxy Sugars

We report the de novo asymmetric synthesis of the 3,6-dideoxy sugars abequose, paratose, and tyvelose from 2-acetylfuran. Conversion of this readily available ketone to a pyranone derivative was followed by transformation to either an α- or β-glycoside via diasteroselective acylation. Michael addition at C2 controlled primarily by the C1 configuration in the glycoside produced 3,6-dideoxy-4-keto sugars, which could be reduced and converted to either fully deprotected monosaccharides or to immediate precursors of glycosyl donors.

Synthesis of threeSalmonellaepitopes for biosensor studies of carbohydrate–antibody interactions

Disaccharides 1-3 corresponding to the antigenic determinants of Salmonella serotypes A, B, and D1were synthesized in a form suited for use in biosensors. The disaccharide determinants each contain a unique 3,6-dideoxyhexose, namely abequose (3,6-dideoxy-D-xylo-hexose), paratose (3,6-dideoxy-D-ribohexose), and tyvelose (3,6-dideoxy-D-arabino-hexose), are α-linked to the 3-position of D-mannopyranose. The disaccharides were further derivatized with a linear aglycon that has a terminal amino group, and can be readily coupled to pertinent chains carrying a terminal thiol for the construction of self-assembled monolayers (SAMs). Efficient routes that employed a single 3,6-dideoxygenation step were developed for the synthesis of paratoside 15 and tyveloside 22.Key words: Salmonella O-antigens, lipopolysaccharide, abequose, paratose, tyvelose, 3,6-dideoxyhexose, deoxygenation, glycoside tethers, immobilization via pentenyl glycosides.

Synthesis of disaccharide congeners of the Trichinella spiralis glycan and binding site mapping of two monoclonal antibodies

The tetrasaccharide epitope, β-D-Tyvp(1[Formula: see text]3)β-D-GalNAcp(1[Formula: see text]4)[α-L-Fucp(1[Formula: see text]3)]β-D-GlcNAcp (1) is the major constituent of the N-glycan expressed on the cell surface of the parasite Trichinella spiralis. Two monoclonal antibodies (Mabs 9D4 and 18H1) that protect rats against infection by T. spiralis bind the terminal disaccharide epitope β-D-Tyvp(1[Formula: see text]3)β-D-GalNAcp conjugated to BSA. The syntheses of disaccharide congeners containing mono-deoxy, mono-methyl, as well as modifications to replace the acetamido group are reported. These target disaccharides were assayed for binding to the protective MAbs. For each antibody different clusters of three hydroxyl groups, that include C-2 and C-4 of tyvelose and for 18H1, the GalNAc acetamido group, provide the key polar interactions with the antibody binding sites. Mapping of the sites by functional group replacement revealed a similar pattern of recognition for the dideoxyhexose by the two MAbs while each recognizes distinct surfaces of the GalNAc residue. Consequently although both antibodies bury the 4-OH of tyvelose, the principal contact surface occurs on opposite sides of the 3,6-dideoxyhexose.Key words: β-tyveloside, 3,6-dideoxy-D-arabino-hexose, Trichinella carbohydrate antigen, antibody mapping, Trichinella spiralis, N-glycans, molecular recognition of carbohydrates, antigen topology, functional group replacement.