Of D-fructose

Another name for glucitol obtained by reduction of d glucose is sorbitol it is used as a sweetener especially in special diets required to be low in sugar Reduction of D fructose yields a mixture of glucitol and mannitol corresponding to the two possi ble configurations at the newly generated chirality center at C 2... 

This cleavage is a retro aldol reaction It is the reverse of the process by which d fruc tose 1 6 diphosphate would be formed by aldol addition of the enolate of dihydroxy acetone phosphate to d glyceraldehyde 3 phosphate The enzyme aldolase catalyzes both the aldol addition of the two components and m glycolysis the retro aldol cleavage of D fructose 1 6 diphosphate... 

Because i.-fructose is the enantiomer of D-fructose, simply look at the structure of n-fructose and reverse the configuration at each chirality center. 

Problem 25.12 Figure 25.5 shows only the jS-pyranose and /3-furanose anomers of D-fructose. Draw the cr-pyranose and n-furanose anomers. 

Manley-Harris and Richards (Missoula, Montana) have compiled a comprehensive account of the dianhydrides of D-fructose and related compounds, more than 30 in all. These compounds, several of which are of importance in the sugar industry, have in the past presented significant problems in their chemical characterization. Their chemistry was surveyed as early as 1945 by McDonald in Volume 2 of this series, and discussed again in Volume 22 by Verstraeten. The current article furnishes detailed NMR data for each of the anhydrides, providing definitive reference data for accurate identification and correlation with earlier literature, where erroneous structural attributions are rather frequent. 

Figure 8.7 Reaction schemes for hydrogenation of d-fructose, d-xylose, and d-lactose.

The taste of D-fructose has been widely studied, and numerous relativesweetness intensity-scores have been assigned to it. Shallenberger and Acree reported that the crystalline solid is 1.8 times as sweet as sucrose. Verstraeten claimed that it is 8 times as sweet, but this must have been a misinterpretation of a statement made by E. G. V. Percival. ... 

By application of first-order, kinetic equations, B. Anderson and Degn claimed that an equilibrated (25°) aqueous solution of D-fructose contains 31.56% of jS-D-fructofuranose and 68.44% of -D-fructopyranose. N.m.r. studies, however, showed that, at equilibrium, a solution of D-fructose contains /3-D-fructopyranose, -D-fructofuranose, a-D-fructofuranose, and a trace of a-D-fructopyranose the distribution of these isomers was shown by gas-liquid chromatography to be 76,19.5, and 4%, respectively. Based on Anderson and Degn s result, Shallenberger reasoned that, as 0.68 X 1.8 = 1.22 (which approximates the reported sweetness of mutarotated D-fructose ), the furanose form(s) must possess very little sweetness. 

Bacterial cellulose, dextran and many other bacterial polysaccharides are composed entirely of D-glucose units the levans are condensation polymers of D-fructose. Dextrans from different species of Leuconostoc... 

It is believed by Schlubach and Sinh35 that the polyfructosans are, as a rule, made up of D-fructose residues joined in a ring. According to these authors, when the methyl derivatives of the polysaccharides are hydrolyzed, the amounts of dimethyl- and tetramethyl-D-fructose formed... 

From these results the authors conclude that irisin is composed of a series of D-fructose units, each member having an additional D-fructose molecule attached. The tetramethyl-D-fructose is thus derived from these dangling D-fructose units. The position of the unions in the rest of the molecule has not been ascertained since the structure of the dimethyl-D-fructose is unknown. 

Difructose anhydrides I, II, and III have been isolated from the nonreducing residue that remains after removal of D-fructose and d-glucose from acid-hydrolyzed inulin. 

The second mechanism (B) likewise does not agree with the results of recent experiments, as compound XI, from the reaction of D-fructose with ethyl acetoacetate, cannot be formed from either of the enolic forms of D-fructose. The structure of the crystalline compound isolated shows that the substituents at Cl and C2 of D-fructose also take part in the condensa-... 

The essentially nonreversible formation of D-fructose 1-phosphate in the muscle-aldolase system is probably attributable to thermodynamic stabilization. D-Fructose 1-phosphate can form a stable pyranose structure, whereas D-fructose 1,6-diphosphate can exist only in the less stable furanose or acyclic forms.72(,) Only when the cleavage products are removed is the monophosphate effectively split under the influence of aldolase. 

Dihydroxyacetone phosphate reacts with D-glycerose in the presence of aldolases of muscle and liver to give D-fructose 1-phosphate (XII) exclusively, whilst DL-glycerose forms equimolar proportions of D-fructose 1-phosphate (XII) and L-sorbose 1-phosphate (XIII).65 Specificity of the enzyme is interesting in the light of Fischer and Baer s observations66 in... 

Jack-bean aldolase and liver aldolase catalyze the conversion of one mole of D-fructose 1-phosphate into one mole each of dihydroxyacetone phosphate and D-glycerose, and the reaction is reversible.73-77... 

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