D-Tyvelose

A similar reaction sequence without the last epimerization would yield D-abequose. CDP-D-tyvelose arises by C-2 epimerization of CDP-D-paratose.65a Other unusual sugars66-68 are formed from intermediates in Eq. 20-11. One is a 3-amino-3,4,6-trideoxyhexose in which the amino group has been provided by transamination67 (see also Box 20-B). 

Ellis, L.A., McVay, C.S., Probert, M.A., Zhang, J., Bundle, D.R. and Appleton, J.A. (1997) Terminal [blinked tyvelose creates unique epitopes in Trichinella spiralis glycan antigens. Glycobiology 7, 383-390. 

Reason, A.J., Ellis, L.A., Appleton, J.A., Wisnewski, N., Grieve, R.B., McNeil, M., Wassom, D.L., Morris, H.R. and Dell, A. (1994) Novel tyvelose-containing tri- and tetra-antennary N-glycans in the immunodominant antigens of the intracellular parasite TrichineUa spiralis. Glycobiology 4, 593-603. 

M. A. Probert, J. Zhang, and D. R. Bundle, Synthesis of a- and /blinked tyvelose epitopes of the Trichinella spiralis glycan 2-Acetamido-2-deoxy-3-0-(3, 6-dideoxy-D-arabmo-hexopyninosyl)-/)-D-galactopyranosides. Carbohydr. Res., 296 (1996) 149-170. 

The biologically important sugars paratose (3,6-dideoxy-D-nho-hexose) and tyvelose (3,6-dideoxy-D-arafctno-hexose) have also been conveniently prepared203 by routes involving reductive dechlorination by hydrogenation over Raney nickel catalyst these 3,6-dideoxy-... 

The derivative (9) of 3,6-dideoxy-a-D-xyIo-hexopyranose (abequose) was isolated from a strain of Salmonella typhimurium,16 that (10) of 3,6-dideoxy-a-D-nfco-hexopyranose (paratose) from Salmonella paratyphi,54 and a mixture of 10 and the ester (11) of 3,6-dideoxy-a-D-arabino-hexopyranose (tyvelose) from Salmonella enteritidis.,6 It was shown that these derivatives are formed from cytidine 5 -(a-D-glu-copyranosyl pyrophosphate) by treatment with nicotinamide adenine dinucleotide (NAD+) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) in the presence of cell extracts of the respective bacterial strain. For example, formation of 9 is characteristic of preparations from Salmonella, group B,55,56 or Pasteurella pseudotuberculosis, type II.56 The derivative 10 was obtained with extracts of Salmonella, group A,56 and Pasteurella pseudotuberculosis, type I and III,56 and a mixture of 10 and 11 with those of Salmonella, group D,55-60 or Pasteurella pseudotuberculosis, type IV 56.59,60 Under similar conditions, the ester (12) of cytidine 5 -pyro-... 

E. H. Williams, W. A. Szarek, and J. K. N. Jones, Synthesis of paratose (3,6-dideoxy-D-rifw-hexose) and tyvelose (3,6-dideoxy-D-orahmo-hexose), Can. J. Chem. 49 796 (1971). 

CDP-6-deoxy-D-xy/o-hexos-4-ulose (7b) serves as a precursor in the biosynthesis of CDP-3,6-dideoxyhexoses28,168 having the d-ribo (paratose, 3,6-dideoxy- D-glucose ), o-xylo (abequose, 3,6-dideoxy- D-galactose ), and d-arabino (tyvelose, 3,6-dideoxy- D-mannose ) configurations. These monosaccharides are characteristic components of O-specific polysaccharides from Salmonella and Yersinia pseudotuberculosis. 

The conversion includes at least three enzymic reactions.169-171 In the first stage, which requires pyridoxamine 5 -phosphate as a cofactor,171,172 dehydration of 7b occurs through intermediate formation of the Schiff base.173 Reduction of the resulting, unsaturated derivative with NADPH, the mechanism of which is not completely clear,174 leads to CDP-3,6-dideoxy-D-eryf/iro-hexos-4-ulose,169 and, in the third stage, further reduction of the latter at C-4 of the hexosyl group produces the derivatives of paratose or abequose the stereochemistry of the reaction is determined by the source of the enzyme.168 The tyvelose derivative is formed as a result of enzymic epimerization at C-2 of the hexosyl group in CDP-paratose.175... 

Dideoxyhexoses. Several bacterial antigenic determinants with the general structure of 3,6-dideoxyhexoses occur in the cell wall of Pasteurella and Salmonella strains. Most of the transformations reported so far occur as cytidine nucleotides (see Table I, References 15, 16, 17, 18, 19). Here, again the first step is the transformation of the cytidine diphospho-linked glucose into its corresponding 4-keto derivative. By at least two distinct steps, requiring NADPH, reduction to several different 3,6-dideoxyhexoses have been reported. One 3,6-dideoxyhexose CDP-tyvelose (3,6-dideoxy-D-arabino hexose) is formed by a specific 2-epimer-ase from CDP-paratose (24). 

Starting from 1,5-anhydro-2,3,4-tri-0-benzoyl-6-deoxy-D-ura >/ o-hex-1 -enitol (48), an unusual approach to the synthesis of disaccharides of serogroup A and D has applied the allylic rearrangement glycosylation procedure of Ferrier [127] to obtain an a-D-< rj//zTO-hex-2-enopyranosyl residue in the disaccharide 49a. Reduction of the 2-enopyranose double bond gave both the paratose (ribo) 49b and tyvelose (arabino) 49c products [28]. 

Glycosides of the disaccharide p-Tyv-(l- 3)-p-D-GalNAc (139)221 and the trisaccharide epitope 140 carrying the challenging (3-1,2-cis-linked tyvelose of the Trichinella antigen were synthesized. The co-amino tether 141 and the fluorescein conjugate 142 of the trisaccharide were described.222... 

The phenyl 1-thioparatoside 145 was activated with TV-iodosuccinimide and silver triflate and reacted with a convenient derivative of the disaccharide (1-d-GalpNAc-(l ->4)-p-D-GlcpNAc. After removal of the pivaloyl-protecting group with sodium methoxide, isomerization of paratose to tyvelose was performed in a one-pot reaction by oxidation with dimethyl sulfoxide and acetic anhydride, followed by reduction with L-Selectride. Selectivity of the reduction was better... 

A. J. Reason, L. A. Ellis, J. A. Appleton, N. Wisnewski, R. B. Grieve, M. McNeil, D. L. Wassom, H. R. Morris, and A. Dell, Novel tyvelose-containing tri- and tetra-antennary V-glycans in the immunodominant antigens of the intracellular parasite Trichinella spiralis, Glycobiology, 4 (1994) 593-603. 

L. A. Ellis, C. S. McVay, M. A. Probert, J. Zhang, D. R. Bundle, and J. A. Appleton, Terminal beta-linked tyvelose creates unique epitopes in Trichinella spiralis glycan antigens, Glycobiology, 7 (1997) 383-390. 

Some of the rare sugars that have been prepared by way of chloro-deoxy derivatives are 4,6-dideoxy-3-0-methyl-D-xyZo-hexose (D-chal-cose), 3,6-dideoxy-D-n foo-hexose (paratose), 3,6-dideoxy-D-arafcmo-hexose (tyvelose), methyl 2,3-dideoxy-/3-D-glr/cero-hex-2-enopyrano-sid-4-ulose, and certain aminodeoxy sugars. 

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