Paratose

Other trivial names that have been used include ascarylose for 3,6-dideoxy-L-arabino-hexose, colitose for 3,6-dideoxy-L-ry/o-hexose and paratose for 3,6-dide-oxy-D-rifeo-hexose. 

Paratose Planteose 3,6-Dideoxy-D-r/bo-hexose a-D-Galactopyranosyl-(1 ->6)-P-D-fructofuranosyl a-D-glucopyranoside... 

An important step in the synthesis of paratose (3,6-dideoxy-n-rtfoo-hexose) involved the conversion of methyl 3-chloro-3-deoxy-/8-D-allopyranoside into methyl 3,6-dichloro-3,6-dideoxy-/8-D-allo-pyranoside in 33% yield.359... 

CDP-PARATOSE EPIMERASE CDP-Choline l,2-diacylglycerol cholinephos-photransferase,... 

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-... 

A solution of methyl 3,6-dichloro-3,6-dideoxy-p-D-allopyranoside (25, 148 mg) in ethanol (50 mL) containing potassium hydroxide (70 mg) and W-4 Raney nickel [27,58] (40 mg) was shaken in an atmosphere of hydrogen for 2 days. A solid product was isolated in the usual manner recrystallization from ethyl acetate-petroleum ether gave methyl 3,6-dideoxy-P-D-nbo-hexopyranoside (35, 89 mg, 86%) mp 63°-65°C, [a]D —60° (c 1.5, MeOH). A solution of methyl 3,6-dideoxy-p-D-ribo-hexopyranoside (35, 86 mg) in 1 N sulfuric acid (10 mL) was heated at 90°C for 5 h. The cooled solution was neutralized with Duolite A-4(OH ) iou-exchange resin and concentrated to yield paratose 36 as a homogeneous (TLC) syrup (61 mg, 78%) R 0.21 [Silica Gel G 6 1 (v/v) chloroform-methanol], [a]D +7° (c 1.1, HzO), in agreement with values reported previously [61,62] for paratose. 

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). 

C. Fouquey, J. Polonsky, and E. Lederer, Synthesis of three 3,6-dideoxyhexoses. Determination of the structure of the natural sugars tyvelose, ascarylose, and paratose, Bull. Soc. Chim. Fr. p. 803 (1959). 

Paramecium 17, 20 Paramylon 170,174 Parathion 636s Parathyroid hormone 314 Paratose 180s Partition coefficient 410 Parvalbumin 312-316 Parvoviruses 244 Patterson map 135 Pauling, Linus C. 83, 84 Paxillin 406... 

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). 

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... 

Such a situation is rather common for D-galactose and the structurally related monosaccharides L-arabinose218 and D-fucose thus far, the latter monosaccharide has been identified only as the furanose form in the O-specific polysaccharide of Eubacterium saburreum.219 6-Deoxy-L-altrose is present as the pyranose in the lipopolysaccharide of Yersinia enteroco-litica,20 but as the furanose in a similar polymer220 of Y. pseudotuberculosis type VB. Paratose, which is usually present in polysaccharides as the a-pyranose, was identified as the /3-furanose in the O-specific polysaccharide221,222 of Y. pseudotuberculosis serotype IB. 

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). 

The branching 3,6-dideoxyhexoses are exclusively a-linked to the main chain mannose residues of the O-polysaccharide and for paratose and abequose this requires the formation of a 1,2-cis-glycopyranoside bond [8]. Thus, glycosyl halides with the ribo and xylo configuration are required with a nonparticipating group at... 

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]. 

A more successful approach was the introduction of the terminal p-tyveloside in the trisaccharide via its epimer, 3,6-dideoxy-D-r/Z>u-hexopyranose (paratose). The paratose glycosyl donor 145 was synthesized through a series of high-yielding steps starting from p-methoxyphenyl (1-D-glucopyranoside 144 (Scheme 41). 

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... 

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