A-D-fructofuranose

P-D-fructofuranose a-D-glucopyranose 1,2 2,1 -dianhydride a-D-fructofuranose a-D-glucopyranose 1,1 2,2 -dianhydride P-D-fructofuranose a-D-glucopyranose 1,1 2,2 -dianhydride P-D-fructopyranose a-D-glucopyranose 1,1 2.2 -dianhydride P-D-fructofuranose a-D-glucopyranose 2,1 3,2 -dianhydride P-D-fructopyranose a-D-sorbopyranose 1,2 2,1 -dianhydride P-D-fructopyranose a-L-sorbopyranose 1,2 2,1 -dianhydride di-a-L-sorbofuranose 1,2 2,3 -dianhydride a-l-sorbofuranose a-L-sorbopyranose 2,1 3,2 -dianhydride di-a-L-sorbopyranose 1,2 2,1 -dianhydride a-D-sorbopyranose a-L-sorbopyranose 1,2 2,1 -dianhydride di p-L-sorbopyranose 1,2 2,1 -dianhydride a-L-sorbopyranose p-L-sorbopyranose 1,2 2,1 -dianhydride a-L-sorbofuranose a-L-sorbopyranose l,2 2,l -dianhydride P-L-sorbofuranose a-L-sorbopyranose 1,2 2,1 -dianhydride a-L-sorbofuranose P-L-sorbofuranose l,2 2,l -dianhydride... 

O-a-D-Galactopyranosyl-a-D-fructofuranose 4-O-a-D-galactopyranosyl-p-D-fructopyranose 1,2 2,1 -dianhydride (31) 3-O-a-D-Glucopyranosyl-QL-D-fructofuranose 3-O-a-D-glucopyranosyl-p-D-fructopyranose 1,2 2,1 -dianhydride (32)... 

Deoxy-6-iodo-a-D-fructofuranose p-D-fructopyranose 1,2 2,1 -dianhydride (49) 6-Chloro-6-deoxy-a-D-fructofuranose p-D-fructopyranose 1,2 2,1 -dianhydride (50) 6-5-Heptyl-6-thio-tt-D-fructofuranose p-D-fructopyranose 1,2 2,l -dianhydride (51) 6-Azido-6-deoxy-a-D-ffuctofuranose P-D-fructopyranose 1,2 2,l -dianhydride (52) 6-Anuno-6-deoxy-a-D-fructofuranose p-D-fructopyranose 1,2 2,l -dianhydride (53) 6-Acetamido-6-deoxy-a-D-fructofuranose p-D-fructopyranose 1,2 2,l -dianhydride (54)... 

Anhydro-a-D-fructofuranose 6-deoxy-6-iodo-p-D-fructofuranose 1,2 2,l -dianhydride (63)... 

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. 

C12H22O1 j H2O 6-O-a-D-Glucopyranosyl-a-D-fructofuranose, monohydrate (isomaltulose, monohydrate palatinose, monohydrate) IMATUL 31 352... 

Figure 9.24 Traditional Fisher and Haworth projections of the ketose, fructose. Fructose can form a five-C ring called a furanose when the C-2 keto group reacts with the hydroxyl on C-5, as shown in a-D-fructofuranose.

Methylation and hydrolysis show that (+)-sucrose contains a D-glucopyranose unit and a D-fructofuranose unit. (The unexpected occurrence of the relatively rare hve-membered, furanose ring caused no end of difficulties in both structure proof and synthesis of (+)-sucrose.) (+)-Sucrose is named equally well as either a-D-glucopyranosyl -D-fructofuranoside or /3-D-fructofuranosyl a-D-glucopyranoside. 

The first report on DFA formation in higher plants dates back to 1933, when Schlubach and Knoop [23] isolated a compound tentatively identified as a-D-fructofuranose p-o-fmctofuranose l,2 2,l -dianhydride (10, also known as DFA I) from Jerusalem artichoke. Alliuminoside, a difructofuranose 2,6 6,2 -dianhydride for which configuration at the glycosidic linkages was not determined, was isolated from tubers of Allium sewertzowi [24], However, the fact that these results have not been further confirmed throws some doubt onto whether the DFAs were actually from plant origin or were formed by the presence of microorganisms. The enzymic formation of a-o-fructofuranose p-o-fructofuranose l,2 2,3 -dianhydride (1, DFA HI) in sterilized homogenates of the roots of Lycoris radiata, a plant use in China as a traditional folk medicine, unequivocally demonstrated the capacity of this plant to produce this particular DFA [25]. The compound was further extracted from the intact bulbs by supercritical carbon dioxide and its structure unequivocally established by NMR [26]. 

Scheme 2 Synthesis of ot-D-fructofuranose P-D-fructopyranose l,2 2,l -dianhydride (9) and a-D-fructofuranose P-D-fmctofuranose l,2 2,l -dianhydride (10) from o-fructose, sucrose and D-fmc-tose oligosaccharides by the action of pyridinium poly(hydrogenfluOTide) complex...

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