5-Keto-D-fructose

Keto-D-fructose, bisdiphenylhydrazone D-Glucosone, monodiphanylhydrazone D-Galactosone, monodiphenylhydrazone,... 

In another recent study it was concluded that both the py-ranose and the furanose forms of the alternate substrate 5-keto-D-fructose act as substrates. The pyranose form can be compared to glucose lacking hydro l at C-1 and having a second hydroxyl at C-2 (ketohydrate form). The furanose form is comparable to fructose but bears an extra hydroxyl moiety at C-5. Correcting for the amount of 5-keto-D-fructose in the pyranose form (98%), a K value for the furanose form could be calculated that is more tfian an order of magnitude smaller than that for fructose. This suggests that there is a favorable interaction between the enzyme and the additional C-5 hydroxyl. However, since no conclusive data for C-... 

Pyrones are also formed from D-fhreo-2,5-hexodiulose ( 5-keto-D-fructose ) (67) when it is heated in aqueous solution.89 Compounds 68 and 69 are formed in high yield, with 68 preponderating. Kojic acid (68) results from /3-eliminations in which the ring remains intact, but the formation of 5-hydroxymaltol (69) requires ring opening, because of the absence of a proton on C-2. 

D-fhreo-2,5-Hexodiulose ( 5-keto-D-fructose ) is mainly (>95%) in the / -pyranose form (7) in aqueous solution98 furanose forms involving... 

The mono- (283) and bis-phosphate (284) derivatives of D-threo-2,5-hexodiulose ( 5-keto-D-fructose, 260) were synthesized enzymically and purified by anion-exchange chromatography. The proportions, ring size, and anomeric configuration were determined by 31P and 13C NMR spectroscopy. Compound 283 was found to exist preponderantly (80%) in the /f-pyranose form, with the remainder being present in the 2R.5R-furanose form. Compound 284 assumes two different furanose forms in solution, one ( 80%) being the 2i ,5i -furanose and the other the 2i ,5S -furanose.500... 

G. Avigad and S. Englard, 5-Keto-D-fructose. I. Chemical characterization and analytical determination of the dicarbonylhexose produced by Gluconobacter cerinus, J. Biol. Chem., 240 (1965) 2290-2296. 

L. Butera, S. Englard, and J. S. Blanchard, Structure of D-t/jreo-2,5-hexodiulose 1-phosphate and D-t/jreo-2,5-hexodiulose 1,6-bisphosphate (5-keto-D-fructose mono-and bis-phosphate) in solution by 13C NMR spectroscopy, Carbohydr. Res., 148 (1986) 179-188. 

A similar double-reductive amination of 5-keto-D-fructose provides a route to pyrrolidines (equation I). This reductive amination also shows some stereoselectivity for the glucitol isomer. 

Skeletal muscle and yeast phosphofructokinases will catalyse the phosphorylation of 5-keto-D-fructose-l,6-bisphosphate (9). The latter has been isolated chromatographically and identified by its phosphorus content and the rather doubtful method of acid lability of the phosphate groups. The bis-phosphate is a competitive inhibitor of the reaction between aldolases and fructose-1,6-bisphosphate probably because of Schiff base formation with the enzyme. ... 

Synthesis from o-fructose D-Fructose has been used for the synthesis of 2R,5S-dihydroxymethyl-31 ,47 -dihydroxypyrrolidine (3) and its analogues (Scheme 4). Thus, microbial oxidation of D-fructose led to 5-keto-D-fructose (24), which was condensed with Ph2CHNH2 to afford a mixture of 25, 26 and 27 in a ratio of 86 8 6. Removal of the benz-hydryl group from 25 by hydrogenation in the presence of Pd(OH)2 afforded 3 in 91 % yield. 

An analogous scheme was revealed in the ammonolysis of 1,3,4,5-tetra-O-benzoyl-jS-D-fructopyranose and 1,3,4,5,6-penta-O-acetyl-keto-D-fructose,37 with formation of the imidazole derivatives 37, 38, 40, 41, and 4(5)-(D-arabino-tetritol-l-yl)imidazole (42), which were identified by paper chromatography. 

J. Defaye and J. M. G. Fernandez, Difructose dianhydrides as synthetic intermediates, Synthesis of 3,6-anhydro-keto-D-fructose, Tetrahedron Asymmetry, 5 (1994) 2241-2250. 

Two methylations of levan by means of dimethyl sulfate and potassium hydroxide (not sodium hydroxide) followed by one inethylation with methyl iodide and silver oxide yielded trimethyllevan in 88% yield. This was purified by solvent fractionation over-all yield 75%, m. p. 145-146°, OCHs 45.9%. Trimethyllevan, hydrolyzed by heating at 95° for twenty-four hours with a dilute solution of sulfuric acid gave a 98.5% yield of a crystalline trimethyl-D-fructose. The trimethyl-D-fructose was proved940 to be 1,3,4-trimethyl-D-fructofuranose since oxidation with nitric acid gave a 97% yield of a dimethyl-2-keto-D-gluco-saccharic acid which was identified as the crystalline diamide (95% yield). 

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