D -Fructose

In contrast to these food applications, the highest industrial non-food application for a fructose compound is attributed to the key compound 

Hydrogenation of HMF leads to 2,5-dimethylfuran, an interesting compound for use as a booster due to its high research octane number. Kuster [20] has reviewed intensively the manufacture of HMF and a detailed review of the synthesis, chemistry, and applications of HMF has been published by Lewkowski [21]. 

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D-fructose, C HijOo. Crystallizes in large needles m.p. 102-104 C. The most eommon ketose sugar. Combined with glucose it occurs as sucrose and rafftnose mixed with glucose it is present in fruit juices, honey and other products inulin and levan are built of fructose residues only. In natural products it is always in the furanose form, but it crystallizes in the pyranose form. It is very soluble in... 

Up to this point all our attention has been directed toward aldoses carbohydrates hav ing an aldehyde function in their open chain form Aldoses are more common than ketoses and their role m biological processes has been more thoroughly studied Nev ertheless a large number of ketoses are known and several of them are pivotal inter mediates m carbohydrate biosynthesis and metabolism Examples of some ketoses include d nbulose l xylulose and d fructose... 

D Fructose (a 2 ketohexose also known as levulose it IS found in honey and IS signficantly sweeter than table sugar)... 

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... 

There is another reaction available to the enediol intermediate Proton transfer from water to C 1 converts the enediol not to an aldose but to the ketose d fructose... 

Following Its formation D fructose 6 phosphate is converted to its corresponding 1 6 phosphate diester which is then cleaved to two 3 carbon fragments under the mflu ence of the enzyme aldolase... 

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... 

Deoxy-1-N-octadecylamlno-D-fructose (2). A solution of N-octadecyl-O-gluco-sylamlne 1 (2 5 g, 5 8 mmol) in pyridine (25 mL] was mixed with 0 28 N HCI (21 mL) in pyridine (5 8 mmoO- Next day, water (200 mL) was added and the product was extracted with a rnixture of 41 BOAc BuOH (200 mL) The organic layer was washed wrth water and dried (Na2S04)... 

The most familiar of all the carbohydrates is sucrose—common table sugar. Sucrose is a disacchar ide in which D-glucose and D-fructose are joined at then anomeric carbons by a glycosidic bond (Figure 25.7). Its chemical composition is the same ine-spective of its source sucrose from cane and sucrose from sugar beets are chemically identical. Because sucrose does not have a free anomeric hydroxyl group, it does not undergo mutarotation. 

FIGURE 7.4 D-Fructose and L-fructose, an enantiomeric pair. Note that changing the configuration only at C5 would change D-fructose to L-sorbose. 

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