Disaccharide polysaccharide synthesis from

The structures of polyprenyl diphosphate-linked intermediates of Salmonella O-specific-polysaccharide biosynthesis were confirmed by chemical synthesis of their analogs derived from the plant polyprenols ficaprenol and moraprenol (structurally related to bacterial polyprenol57) with the following study of their behavior as substrates of enzymic reactions. Synthetic polyprenyl a-D-galactopyranosyl diphosphate291,292 was found to serve as an effective acceptor for the transfer of L-rhamnosyl groups.293"295 Two synthetic, isomeric disaccharide derivatives,292 13 and296 14, were tested as acceptors for enzymic D-mannosyl transfer from GDP-Man, but only the former was found to be an efficient substrate.294... 

Synthesis of f -D-(l,6) linked disaccharides of N-fatty acylated 2-amino-2-deoxy-D-glucose an approach to the lipid A component of the bacterial lipopolysaccharide. Carbohydr. Res., 88, C10-C13 Kochetkov, N.K., Dmitriev, B.A., Malysheva, N.N., Chernyak, A.Ya., Klimov, E.M., Bayramova, N.E., and Torgov, V.I. (1975). Synthesis of O-p-D-mannopyranosy l-( 1 - 0-0-ot -L-rhamnopyranosy l-( 1 -3)-D-galacto-pyranose, the trisaccharide repeating-unit of the O-specific polysaccharide from Salmonella anatum. Carbohydr. Res. 15, 283-290... 

From this brief survey, it is seen that there were few features of carbohydrate metabolism in plants that escaped Hassid s touch, and much that we now know about the role of sugar nucleotides in the interconversion of carbohydrates in plants is a direct result of his persistent effort. From the incorporation of labelled precursors into monosaccharides, to the conversion of the monosaccharides into their glycosyl phosphates, to the action of the pyrophosphorylases in the synthesis of glycosyl esters of nucleoside pyrophosphates, to the interconversion of the resulting sugar nucleotides, to the polymerization of the activated monosaccharides to yield disaccharides and the homopolysaccharides, and, finally, to the modification of the polysaccharides by methylation—in summary, to almost every aspect... 

The native bacterial GAG glycosyltransferase polypeptides are associated with the cell membranes this localization makes sense with respect to synthesis of polysaccharide molecules destined for the cell surface. The first Pasteurella GAG synthase to be identified was the 972-residue HA synthase from Type A strains, pmHAS (Table I). This single polypeptide transfers both sugars, GlcNAc and GlcUA, to form the HA disaccharide repeat (i). 

Block synthesis has also been employed to produce the pentasaccharide repeating unit (22) of the O-specific polysaccharide of S. Strasbourg, The orthoester method allowed condensation between units from which the disaccharide at the reducing end and the trisaccharide at the non-reducing end were derived. Compounds (23)-(26) were used in the synthesis of the linear compound a-D-gal NAc-( 1 3 )- 3-D-gal NAc-( 1- 3 )-o -D-gal-( 1 4)-/ -D-gal-( 1 4)-D-glc which... 

The usefulness of dispiroketal to act as practical glycosyl donors was further illustrated in a facile one-pot synthesis of a trisaccharide fragment from the capsular polysaccharide of Group B Streptococci [80]. In the following example (Scheme 29), armed perbenzylated ethyl l-thio-oj-L-rhamnopyranoside donor 157 was treated with semidisarmed dispiroketal 158 under IDCP promoted glycosylation to provide disaccharide 159 in 59% yield. Glycosidation of acceptor 159 with acceptor 160 with the more potent NIS/TfOH couple afforded protected... 

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