D-Fructose, l-

D,L-Mannitol has been obtained by sodium amalgam reduction of D,L-mannose. The identical hexitol is formed from the formaldehyde polymer, acrose, by conversion through its osazone and osone to D,L-fructose (a-acrose) followed by reduction (83). 

L-Fructose does not occur naturally. Fischer11 showed that part of the mixture of hexoses called acrose which he obtained synthetically could be converted through the osone to D,L-fructose. Treatment of this by yeast left L-fructose. This sugar has also been synthesized from L-ara-bonic acid by Wolfrom and Thompson.12... 

An attempt has been made by Hersant and Linnell146 to isolate 5-methyl-D,L-fructose from the products obtained when dihydroxyacetone condenses with D,L-/ -hydroxy-a-methoxypropionaldehyde, but their results are inconclusive. 

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. 

The presence of asymmetric carbon atoms also confers optical activity on the compound. When a beam of plane-polarized hght is passed through a solution of an optical isomer, it will be rotated either to the right, dextrorotatory (+) or to the left, levorotatory (—). The direction of rotation is independent of the stereochemistry of the sugar, so it may be designated d(—), d(+), l(—), or l(+). For example, the naturally occurring form of fructose is the d(—) isomer. 

Franke, D., Machajewski, T., Hsu, C.-C. and Wong, C.-H. (2003) One-pot synthesis of L-fructose using coupled multienzyme systems based on rhamnulose-1-phosphate aldolase. The Journal of Organic Chemistry, 68 (17), 6828-6831. 

Fig. 1.—Fischer s Total Synthesis of D-Glucose, D-Mannose, and D-Fructose and of L-Glucose, L-Mannose, and L-Fructose.

Among many other methods for epoxidation of disubstituted E-alkenes, chiral dioxiranes generated in situ from potassium peroxomonosulfate and chiral ketones have appeared to be one of the most efficient. Recently, Wang et /. 2J reported a highly enantioselective epoxidation for disubstituted E-alkenes and trisubstituted alkenes using a d- or L-fructose derived ketone as catalyst and oxone as oxidant (Figure 6.3). 

Both D-[l- C]xylose and D-[5- C]arabinose were exposed to a concentrated phosphate buffer solution (pH 6.7). 1-Hydroxy-2-propanone (ace-tol) was distilled from the heated solution. Radioassay indicated that similar labeling [3- C] occurred in the acetol from both pentoses, with loss of the configurational difference thus, a 3-ketopentose or its enediol was suggested as an intermediate. Further work with 3-0- and 6-0-methyl-D-glucose and with 1-0-methyl-D-fructose indicated that /3-elimination from a 3-ketose or, in the case of a hexose, from a 3-ketose or a 4-ketose, or both, tautomerization of the resulting a-diketone to a /3-diketone, and hydrolytic cleavage are essential steps in the formation of acetol. 

In 1996, ketone 26 was reported to be a highly effective epoxidation catalyst for a variety of trans- and trisubstituted olefins [53]. Ketone 26 can be readily synthesized from D-fructose by ketalization and oxidation (Scheme 2) [54-56]. The enantiomer of ketone 26 (ent-26) can be obtained by the same methods from L-fructose, which can be obtained from L-sorbose [57, 58]. 

The first, total synthesis of sugar-like compounds was performed as early as 1861 in that year, Butlerov2 reported the formation of methylenitan on treatment of aqueous formaldehyde with calcium hydroxide. The first, defined sugar derivative, DL-mannitol ( a-acrit ), was obtained by Emil Fischer and Tafel,3 and the first, optically active, totally synthetic sugars, D- and L-mannose and D- and L-fructose, were also prepared by Fischer.4... 

Scheme 14 Biosynthesis of the C5 unit of thiamin from isotopically labelled hexoses. Label from D-[l-14C]glucose and D-[l-uC]fructose label C-4 exclusively D-[2-14C]glucose labels C-4 and C-4 equally D-[6-14C]glucose labels C-4 (16% of 14C incorporated the precise location of the remaining 14C was not determined) d-[6-D2]glucose gives rise to both [4 -D2]- and [7-D2]-thiamin...

Recognition systems in animal cells have been extensively reviewed. Some examples include the D-galactose- and L-fructose-recognition system of mammalian hepatocytes,233,234 the 2-acetamido-2-deoxy-D-glucose-recogni-... 

Exercise 15-15 How can D-glucose, D-fructose, and D-ribose be considered products of the addition of an alcohol to the carbonyl group of an aldehyde or ketone Name each of the carbonyl compounds by the IUPAC system. For the ribose carbonyl structure, determine the configuration at each chiral center, using the D,L system. 

The aqueous oxidation of D-[l-14C]glucose and D-[6-14C]glucose at 100 °C afforded formic, acetic, and glycolic acids, and carbon dioxide. The last is mainly produced from C-2 to C-5, the formic acid from C-l, and the acetic acid from C-6.96 Addition of aluminum(III) chloride greatly increased the yield of carbon dioxide. Oxidation of D-glucose and D-fructose, studied with lsO-enriched oxygen, showed that they decompose via the C-l and C-2 hydroperoxides to give D-erythronic acid as the main product.76... 

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