6-Deoxy-D-talose

Non-stereospecific reduction of GDP-6-deoxy-D-/yxo-hexos-4-ulose (7c) to derivatives of 6-deoxy-D-mannose (D-rhamnose) and 6-deoxy-D-talose (see Section III,l,c) was found to occur with an enzyme from an unidentified,... 

Formation of the identical sugars of the D-series, 6-deoxymannose (rhamnose) and 6-deoxytalose, seems to proceed by a different pathway. According to Winkler and Markowitz (13), GDP-6-deoxy-D-mannose is first converted to GDP-6-deoxy-D-lyxo-4-hexulose. This 4-keto intermediate is the direct precursor for the unspecific enzymatic reduction leading to GDP-6-deoxy-D-mannose and GDP-6-deoxy-D-talose. For a pyridine-nucleotide requiring enzyme, the transformation seems to be unusual because of its lack of stereospecificity. However, closer examination and evaluation of properties of the different 4-keto-intermediate reductases must await availability of more highly purified enzyme preparations. 

Nao S, Yoshio N, Yasuo Y et al (2002) Guanosine diphosphate-4-keto-6-deoxy-D-mannose reductase in the pathway for the synthesis of GDP-6-deoxy-D-talose in Actinobacillus actinomycetemcomitans. Eur J Biochem 269 5963-5971... 

D-Fucose, in the furanose or pyranose form, has been identified in bacteria. Actinobacillus actinomycetemcomitans strains, of all serotypes, commonly produce polysaccharide antigens consisting of 6-deoxyhexoses. In fact, the serotype b-specific polysaccharide antigen from A. actinomycetemcomitans Y4 consists of the following disaccharide repeating-unit -3)-a-D-Fuc/4 I 2)-a-i.-Rha/u( I. l92 On the other hand, serotype a consists solely of 6-deoxy-D-talose and serotype c is a polysaccharide of the l enantiomer.175... 

A reaction catalyzing the inversions at C-3 and C-5 is postulated to occur in the formation of GDP-L-galactose from GDP-D-man-nose also, the synthesis of 6-deoxy-D-talose from GDP-D-mannose is assumed to involve a reduction at C-6 and inversion at C-4. 

There have been many reports of syntheses of deoxy nucleosides by standard sugar-base condensation reactions. These include 5 -deoxy-ribo nucleosides and 5 -mono- or 5",5-di-deuterated analogues, as well as derivatives of 5-deoxy-D-xylose and 5-deoxy-D-glucose, 5-alkylated thymidine derivatives, 2 -deoxy-6-methyl-5-azacytidine and its a-anomer, the thymidine analogue 4-(2-deoxy-B-D-erythro-pento-furanosyl)-6-methyl-l,2,4-triazine 3(HH)-one-1-oxide, 6-aza-3-deaza analogues of 2 -deoxy-cytidine and 2 -deoxyuridine,3 -deoxycytidine from a 3-deoxy-ribofuranose obtained from a fermentation broth producing the 3 -deoxy nucleoside antibiotic, cordycepin, 4-deoxy-DL-threo-pentopyranosyl pyrimidine nucleosides, and 5 -C-methyluridines derived from 6-deoxy-D-allose and 6-deoxy-D-talose. A range... 

Conversion of L-fucosyl- and 3 -0-methyl-D-glycosyl-purines into nucleosides of two naturally occurring, rare sugars, 6-deoxy-L-talose and 3-O-methyl-D-mannose, could be achieved57 by stereospecific reduction at C-2 of 7-(6-deoxy-3,4-0-isopropylidene-/ -L-h/xo-hexopyranosyl-2-ulose)theophylline (35a) and 7-(4,6-0-benzylidene-3-0-methyl-/ -D-orobtno-hexopyranosyI-2-ulose)theophylline (8). Treatment of 35a and 8 with sodium borohydride in ethanol afforded the expected 7-(6-deoxy-3,4-0-isopropylidene-/ -L-talopyranosyI)theophylline (84) and 7-(4,6-... 

Desulfonylation of 2-O-p-tolylsulfonyl or 2-0-(methylsulfonyl) derivatives of D-arabinose, D-xylose, and L-fucose with aqueous barium hydroxide yields D-ribose, D-lyxose, and 6-deoxy-L-talose, respectively, by way of a 1,2-anhydro sugar similarly, 3-0-(methyl-sulfonyl)-D-fructose affords D-psicose. 

SCHEME 13. 33 Mukaiyama s asymmetric aldol reactions total synthesis of D-ribose, 4-C-methyl-D-ribose and 6-deoxy-L-talose. 

The exopolysaccharide of Burkholderia caribensis strain MWAP 71 contains 6-deoxy-L-talose.178 Other strains of Burkholderia pseudomallei incorporate 6-deoxytalose, as a polymer with D-glucose but its configuration has not been established.174... 

The sugars from the nucleoside-like antibiotics have been discussed in Section III,5. These are cordycepose (29), D-psicose (30), angustose (33), and amicetose (39). From actinospectacin, the unusual actinospectose (46) was obtained. Hygromycin and hygromycin B have yielded two novel products, 6-deoxy-D-om6mo-hexos-5-ulose (49) and D-talose (51). Novobiocin contains the sugar derivative called noviose (54). 

Chemical Synthesis.—Purine nucleoside 5 -monophosphates enriched with or 0 on the phosphate group are conveniently prepared by treating phosphorus pentachloride in dry triethyl phosphate with one equivalent of the appropriately labelled water to give PO]- or P 0]P0Cl3, which is not isolated but mixed with adenosine or guanosine in the same solvent. Work-up of the resulting 5 -phos-phorodichloridate in similarly labelled water permits the formation of pO]-or P 0]AMP (or GMP) in fair yield with good enrichment. The 5 -monophos-phates of the 5 -C-methyl uridines derived from 6-deoxy-D-allose and 6-deoxy-L-talose have been prepared via phosphorylation of the 2, 3 -0,0-ethoxymethyl-idene derivative of the nucleosides (1) with -cyanoethyl phosphate and DCC or TPS-Cl. The same method has been used to phosphorylate iV -benzoylated 2, 3 -0,C -isopropylidene derivatives of various 5 -C-alkyladenosine species (2) and also 4 -allyladenosine (3) as part of a study in which derivatives of AMP... 

A number of 6-deoxyhexoses also are widespread in plants, but these compounds are especially common in cardiac glycosides (Courtois and Percheron, 1970). These sugars are formed from the corresponding hydroxylated monosaccharides (Luckner, 1990). Among the 6-deoxyhexoses are L-acofriose (6-deoxy-3-0-methyl-L-mannose) (18), l-acovenose (6-deoxy-3-6>-methyl-L-talose) (19), o-allometh-ylose (6-deoxy-D-allose) (20), L-altromethylose (6-deoxy-L-altrose) (21), D-antiarose (6-deoxy-o-gulose) (22), D-boivi-nose (2,6-dideoxy-D-xy/o-hexose) (17), D-cymarose (2,6-di-... 

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