Difructose anhydrides from inulin

A possible mechanism for the origin of the difructose anhydrides from inulin has been suggested by McDonald and Jackson7 in the following paragraph ... 

Jackson and Goergen16 found that when D-fructose was treated with sulfuric acid under conditions similar to those used in preparing the difructose anhydrides from inulin, no condensation of the D-fructose took place. 

In 1933, Schlubach and Knoop32 isolated a di-D-fructose dianhydride from Jerusalem artichoke and tentatively identified it as difructose anhydride I [a-D-Fru/-1,2 2,1 - 3-D-Fn / (5)]. Alliuminoside ( -D-fructofuranose- -D-fructofura-nose 2,6 6,2 -dianhydride) was isolated from tubers of Allium sewertzowi by Strepkov33 in 1958. Uchiyama34 has demonstrated the enzymic formation of a-D-Fru/-1,2 2,3 -(3-D-Fru/ [di-D-fructose anhydride III (6)] from inulin by a homogenate of the roots of Lycoris radiata Herbert. 

An extracellular inulin fructotransferase that results in the formation of a-D-Fru/-1,2 2,1 -(3-D-Fru/ [difructose anhydride I (5)] has been purified from Arthrobacter globiformis S14-3,65,66 from Arthrobacter sp. MCI-249367 and from Streptomyces sp. MCI-2524.68... 

A mechanism was proposed31 for the formation of di-D-fructose dianhydrides from inulin and fructose. It was suggested that a-D-Fru/-1,2 2,1 - 3-D-Fru/ [difructose anhydride I (5)] formed first and then isomerized via ionic intermediates to produce the remaining products. Important support for the concept of the reversibility of the isomerization was the observation that ot-D-Frup-1,2 2,1 - 3-D-Frup (4) and p-D-Frup-1,2 2,1 - 3-D-Frup produced, upon treatment with HF, the same product mixture as did D-fructose. 

Irisin — tetrafructose anhydride — difructose anhydride —> D-fructose. The difructose anhydride, although not isolated in pure form, was readily hydrolyzed by acid and thus differed from the difructose anhydrides isolated from inulin. 

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. 

Difructose anhydride II reacts with one mole of per-iodic acid. Hydrolysis of its methyl derivative indicates that two different trimethyl-D-fructoses are formed whose combined specific rotations in water amount to between + 20° and + 30°. If we assume that this anhydride, like the other two derived from inulin, is made up of D-fructofuranoses, the facts that have been mentioned allow only three possible structures for this anhydride. 

Inulin, Dahlin alantin alant starch. Mol wt approx 5000. Polysaccharide of Compositae which partially or completely replaces starch as a reserve food. Isoln from dahlia tubers McDonald, "Polyfructosans and Difructose Anhydrides" in Advan. Carbohyd. Chem. vol. 2, 254 (1946) from Jerusalem artichoke tubers Bacon, Edelman, Biochem. J. 48, 114 (1951). Structure E. G. V. Percival. Structural Carbohydrate Chemistry (J. Garnet Miller, London, 2nd ed., 1962) p 274. 

Jackson and Goergen 133) and Jackson and McDonald 134) have isolated three dianhydrides of D-fructose from the nonreducing residue that remains after the removal of D-fructose from the acid hydrolyzate of inulin 135). On the basis of methylation data 136), structure (III) was assigned to difructose anhydride I. Difructose anhydride III was considered 135) to be di-D-fructofuranose l,2 2,3 -dianhydride. Wolfrom, Hilton, and Binkley 129) believe, on the basis of rotational data, that difructose anhydrides II and III are structural units differing only in the configuration of one of the asymmetric centers on the substituted dioxane ring. 

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