Fructose preparation

Fructose, prepared from hydrolysis of sucrose and isomerization of glucose is used in the manufacture of candy, soft drinks, and other processed foods. As fructose is 124 percent as sweet as sucrose, substitution of fructose for sucrose in foods permits a reduction in the calorie content of a food. 

Comments an equimolecular mixture of dextrose and fructose prepared by the hydrolysis of sucrose with a suitable mineral acid such as hydrochloric acid. Invert sugar may be used as a stabilizing agent to help prevent crystallization of sucrose syrups and graining in confectionery. A 10% aqueous solution is also used in parenteral nutrition. 

Bredereck and coworkers also studied the 1,6-ditrityl ether, and definite proof of its structure was afforded by an outstanding series of experiments. The amorphous material (m.p. 94r-96°) was treated with the ordinary acetylation mixture, and yielded 3,4,5-tri-O-acetyl-l,6-di-O-trityl-fce(o-D-fructose. Preparation of the oxime followed by further acetylation gave the crystalline acetate of the oxime [ m.p. 207-208° Ca ]D - -118° (in chloroform)]. < The oxime of l,6-di-t>-trityl-D-fructose affords the same product on acetylation. The keto form was proved by formation of the crystalline diethyl dithioacetal from the acetyl derivative. 

Zervas and Sessler synthesized an isomeric mono-O-isopropylidene-D-fructose by acetonating 1,6-di-O-benzoyl-D-fructose, prepared by treatment of D-fructose cyanohydrin with two molar proportions of benzoyl chloride in the presence of pyridine. The cyclic acetal obtained after debenzoylation was named 2,3-acetone-a-D-fructo-furanose by the authors, although, quite evidently, it is 2,3-0-isopropylidene-j8-D-fructofuranose (90). 

Isoglucose is an equilibrium mixture of glucose and fructose prepared from cornstarch. It is a substitute for invert sugar, which is a 1 1 mixture of glucose and fructose prepared from sucrose. Starch is a mixture of the glucose polymers amylose (39) and amylopectin (40). The former contains... 

As part of a study on the structural features responsible for the intense sweetness of D-fructose, 3-deoxy-D-fructose, prepared by a literature procedure... 

Cyclopentane rings can also be formed readily by treating 6-deoxy-6-nitro-D-fructose (prepared enzymatically from dihydroacetone phosphate and 3-deoxy-3-nitro-D,L-glyceraldehyde in the presence of an aldolase then phosphatase) with acetic anhydride and boron trifluoride etherate, then subjecting the mixture to chromatography on silica gel thereby affording 63 and the epimer at the indicated carbon atom. ... 

Benzoates. Benzoyl chloride has a very limited application as a reagent in the sugar series, but it is useful for the preparation of a crystal line derivative of glucose and of fructose. 

In a 50-100 ml. conical flask place a solution of 0 -5 g. of glucose in 5 ml. of water, 12-15 ml. of 10 per cent, sodium hydroxide solution and 1 ml. of benzoyl chloride, cork tightly, and shake until the odour of benzoyl chloride has disappeared and a crystalline (frequently sticky) soUd has separated. Filter oflF the solid, wash it with a Uttle water, and recrystaUise it from ethyl or n-butyl alcohol. (If the product is sticky, it should be removed, and spread on a porous tile before recrystaUisation.) Glucose pentabenzoate has m.p. 179°. Fructose pentabenzoate, m.p. 78-79°, may be similarly prepared. 

Similar anomalous distributions are observed in other thermal product mixtures. A commercial soft caramel made by heating sucrose and 0.1% acetic acid to 160°C contained 18% of a mixture of di-D-fructose dianhydrides.94 fi-D-Fru/-1,2 2,1 - 3-D-Fru/(now assigned as a-D-Fru/-l,2 2,l -a-D-Fru/83), ot-D-Fru/-1,2 2,1 -p-D-Fru/(5), ot-D-Frup-1,2 2,l -0-D-Fnjp (4), ot-D-Fru/-l,2 2,1 - 3-D-Frup (1), and p-D-Fru/-l,2 2,3 - 3-D-Fru/ (2) were found in the ratio 4 12 1 6 2. The first three of these, constituting 68% of the mixture, are considered to be kinetic products. The authors commented on this, but did not offer any explanation. Notice, however, that the preparation of such commercial caramels commences with heating of an acidic aqueous solution of sucrose, which almost certainly results in hydrolysis. Hence, the final dianhydrides are probably derived from the reaction of fructose, rather than sucrose. 

Tschiersky and Baltes96 prepared di-D-fructose dianhydrides by heating fructose. Mass spectra of the permethyl ethers were obtained. Although the dianhydrides were of unknown structure, examination of the spectra indicate that all are difuranose dianhydrides (mlz 101 as the base peak, and low intensities of the ions mlz 88 and 277) and at least one is reminiscent of a 2,3-linked difuranose structure (relatively intense mlz 363 [M — 45]+).95-98... 

The raw materials from which di-D-fructose dianhydrides can be obtained in appreciable yield are readily available from comparatively inexpensive agricultural feedstocks. Thus, these compounds are attractive as chiral-starting materials for chemical synthesis. Their stability to acid and heat, and their relative rigidity, because of the conformational constraints covered here, are also features that might be exploited during syntheses.119 A series of variously substituted di-D-fructose dianhydrides has been prepared,119 starting from 6,6 -dideoxy-6,6 -di-halosucroses. The properties of these and other derivatives of di-D-fructose dianhydrides are summarized in Tables XIV-XX. Two of these derivatives, 48 and 56, exhibit thermotropic liquid-crystal properties.119... 

The most convenient method is the formation of two equivalents of (25) by retro-aldol cleavage from commercially available (26) by the combined action of FruA and triose phosphate isomerase (Figure 10.18 inset) [84]. This scheme has been extended into a highly integrated, artificial metabolism for the efficacious in situ preparation of (25) from inexpensive feedstock such as glucose and fructose (two equivalents of... 

Figure 10.18 Enzymatic in situ generation of dihydroxyacetone phosphate from fructose 1,6-bisphosphate (b), with extension to an in vitro artificial metabolism for its preparation from inexpensive sugars alongthe glycolysis cascade (a), and utilization for subsequent stereoselective carbon-carbon bond formation using an aldolase with distinct stereoselectivity (c).

Deoxy-4-fluoro-D-fructose (552) was prepared (59%) by fermentation of 3-deoxy-3-fluoro-D-mannitol with Gluconobacter oxydans. The structure of 552 (fi-T) form) was confirmed by the n.m.r. spectrum, which resembles that of 4-deoxy-4-fluoro-Q -D-sorbopyranose (553) 552 was identical with one of the products obtained from the oxirane-ring opening of 3,4-anhy-dro-l,2-0-isopropylidene- -D-tagatopyranose with KHFj. 

With the experimental results accumulated during his stay in Berlin, Garcia Gonzalez prepared two doctoral dissertations, entitled New Crystalline Phosphoric Esters of o-Fructose and Tests on Some Assumed Phases of Alcoholic Fermentation, which he presented in order to receive his doctorates in Chemistry and in Pharmacy, respectively, at the University of Madrid in 1932. Armed with these two degrees, he decided to pursue an academic career in his own country. His early training in a provincial... 

Other compounds identified in caramels are di-D-fructose and poly(glycosyl) dianhydrides (DFAs). DFAs were found in caramels prepared from D-fructose, D-glucose, and sucrose. The analysis was done after derivatization as TMS (per-0-trimethylsilyl) derivatives or as TMS-oxime (per-O-trimethylsilyl oxime) by... 

Competitive reduction of Au(III) and Ag(I) ions occurs simultaneously in solution during exposure to neem leaf extract leads to the preparation of bimetallic Au-core/Ag-shell nanoparticles in solution. TEM revealed that the silver nanoparticles are adsorbed onto the gold nanoparticles, forming a core/sheU structure. Panigrahi et al. [121] reported that sugar-assisted stable Au-core/Ag-shell nanoparticles with particles size of ca. 10 nm were prepared by a wet chemical method. Fructose was found to be the best suited sugar for the preparation of smallest particles. 

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