Hexos-5-ulose

Example CH=N-NHPh 1 CH = N—NHPh HOCH HCOH HCOH i ch2oh D-araib/no-Hexos-2-ulose bis(phenylhydrazone)... 

D-arab/no-Hexos-2-ulose phenylosotriazole or (1 fl)-1-(2-phenyl-2H-1,2,3-triazol-4-yl))-D-erythritol or 2-phenyl-4-(D-arab/no-1,2,3,4-tetrahydroxybutyl)-2H-1,2,3-triazole... 

Scheme 16 shows that 3-deoxy-D- ry < -hexos-2-ulose (39) can be formed by the cleavage of a diketosamine. Such an intermediate has already been implicated in the formation of 5-(hydroxymethyl)-2-furalde-hyde (see Scheme 7). Interest in 39 and its formation is directed towards its role in the production of two major groups of products observed in...

In the presence of molecular oxygen, D-arabinose (82) is the major deamination product. D-tfrafeino-Hexos-2-ulose (79) is also formed, but the formation of 2-deoxy-D-hexonic acid (80) and 2-deoxy-D-ert/fhro-hexos-3-ulose (81) is suppressed. It has been suggested34 that the peroxyl radical derived from the W-centered radicals (78) may be, in part, the precursor of D-arabinose. A mechanism similar to the... 

In this reaction sequence, 11 was not isolated, but, when the same series of reactions was conducted starting with D-crafctno-hexos-2-ulose (D-glucosone, 12), the cyclic imine 13 was isolated.77... 

In addition, L-sorbose (25) has been converted into L-xty/o-2-hexulo-sonic acid (28) by way of L-xiy/o-hexos-2-ulose (44) by using mixtures of Gluconobacter melanogenus IFO 3293 and Pseudomonas syringae NRRL B-865 immobilized in a poly(acrylamide) gel.305 The yields were, however, low. 

One of them involves the enzymes D-glucose-l-oxidase (EC 1.1.3.4) and pyranose-2-oxidase (EC 1.1.3.10). An alternative enzymatic pathway (Scheme 9, Path b) requires the same two enzymes, but proceeds through the intermediate o-arabino-hexos-2-ulose, D-glucosone, (107) the enzyme catalase can be used to decompose the H202.283... 

It has been suggested that D-arabino-hexos-2-ulose (205) is formed by metal-catalyzed autooxidation of glucose.410... 

The 3-deoxyhexos-2-uloses, which had long been hypothesized as intermediates in many important degradation reactions of carbohydrates, have been isolated and studied,412 in particular, 3-deoxy-D- erythro-hexos-2-ulose 3-deoxyglucosone (206), which is found in higher concentrations in diabetic animals.413 In mammals, a significant proportion of 206 is reduced to form 3-deoxy-D-eryt/ ro-hexos-2-ulose (3-deoxy-D-fructose, 207), which was detected in blood and urine. This conversion is likely to be biologically useful, since 207 would be less reactive, and therefore less damaging than 206. 

A synthesis of D-tagatose from D-galactose proceeds via the hexos-2-ulose derivative 212, which was obtained by oxidation under Moffatt conditions from 211 and exists as the tautomeric form 213.426... 

Wood-degrading fungi produce a family of pyranose oxidases (EC 1.1.3.10), enzymes catalyzing the oxidation at C-2 of several aldoses. A simple and convenient conversion of D-glucose into D-arabino-hexos-2-ulose involves the use of a pyranose-2-oxidase isolated from Polyporus obtusus, which was purified and immobilized on activated CH-Sepharose 4B.446... 

A quinone-dependent sugar oxidoreductase, purified from Agaricus bisporus, catalyzes C-2 and C-3 oxidation of D-glucose to o-arabino-hexos-2-ulose and preferentially to D-n fto-hexos-3-ulosc. The two aldoketoses accumulate transiently in the reaction mixture, being converted into the same end-product, D-eryt/zro-hexos-2,3-diulose. D-Galactose is oxidized exclusively at C-2 to produce D - /y.w - h c x o s - 2 - u 1 o s c.447 Fukui and Hochster448 prepared n-/vAo-hexos-3-ulose (219) by enzymic oxidation and hydrolysis of sucrose. 

D-arabino Hexos-2-ulose (205) reacts with methanolic hydrogen chloride to afford D-arabino-hexos-2-ulose 1,1-dimethyl acetal (235) and the crystalline methyl /f-D-ara/)/ u-hexos-2-ulose-2,5-furanoside 1,1-dimethyl acetal (236) as the main components.451... 

Crude enzyme extracts from the white-rot fungus Oudemansiella mucida oxidize D-glucose to D-pryt/zro-hexos-2,3-diulose (265) via o-arabino-hexos-2-ulose. Compound 265 was identified by NMR and mass spectroscopy of the N, N- di p he n y 1 h y dr a zo ne derivatives 491... 

J. Geigert, S. L. Neidleman, D. S. Hirano, B. Wolf, and B. Panchar, Enzymic oxidation of D-araWrco-hexos-2-ulose (D-glucosone) to D-arabino-2-hexulosonic acid ( 2-keto-D-gluconic acid ), Carbohydr. Res., 113 (1983) 163-165. 

At low temperatures, D-glucose and D-fructose in the presence of ferrous sulfate are converted into D-uru/u770-hexos-2-ulose (36), which can be degraded by further oxidation to glycolic acid, glyoxylic acid, and D-erythronic acid. The nature of the products formed under various conditions and the mechanism of the reaction have been described (see Ref. 1, p. 1133). In dilute solution, in the presence of ferrous sulfate at low temperature, compound 36 gave D-ura mo-2-hexulosonic acid (37) and D-ery//zro-hexo-2,3-diulosonic acid (38). In concentrated solutions, formaldehyde was also found. The formation of these products at low temperature was ascribed to the series of reactions in Scheme 19. 

The most important ketoses are the hexos-2-uloses H0CH2(CH2) 3C0CH20H, such as fructose. They have one less chiral centre than the aldoses of the same chain length i.e., there are only four diastereomerically different hexos-2-uloses. 

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