Di-D-fructose dianhydrides

Isolation of Di-D-fructose Dianhydrides from Higher Plants. 213... 

Acid Hydrolysis of Di-D-fructose Dianhydrides and Their Per-O-methyl... 

Di-D-fructose dianhydrides were first reviewed in 1946 as part of a chapter1 in this Series. That work described the outcome of a burst of activity in this field,... 

The literature in this field is confusing because of a somewhat haphazard method of nomenclature that has arisen historically. This is compounded by some mistakes in structure determination, reported in early papers, and which are occasionally quoted. The first part of this chapter deals with nomenclature and with a brief overview of early work. Subsequent sections deal with the formation and metabolism of di-D-fructose dianhydrides by micro-organisms, and the formation of dihexulose dianhydrides by protonic and thermal activation. In relation to the latter topic, recent conclusions regarding the nature of sucrose caramels are covered. Other sections deal with the effects of di-D-fructose dianhydrides upon the industrial production of sucrose and fructose, and the possible ways in which these compounds might be exploited. An overview of the topic of conformational energies and implications for product distributions is also presented. 

Historically, the trivial names diheterolevuloson 1, 11, III, and IV have been used to describe the di-D-fructose dianhydrides, which contain one or two pyra-nose rings. Similarly, the names di-D-fructose dianhydride (or difructose anhydride) 1,11, III, IV, and V have been used to describe those compounds in which two furanose rings occur. The names diheterosorhosan I and II have also been coined. Trivial names should not be used in other than a secondary manner for example, they may be listed in parentheses after the IUPAC name. 

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. 

The biosynthesis and degradation of fructans by microbial organisms has been reviewed in detail recently.35 Additionally, a review of the production of di-D-fructose dianhydrides from inulin and levan by enzymes has been published in Japanese.36 This account is therefore limited to a general overview. 

It is obvious that there remain unanswered a number of interesting questions relating to the role of the di-D-fructose dianhydrides in Nature. First, it is not... 

Little information is available on the specific control of fructan metabolism in higher plants73 or in microorganisms.35 If a regulatory role is envisaged for the di-D-fructose dianhydride enzymes, as has been suggested for microorganisms,71 then more detailed studies are required. 

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. 

Thermal activation of sucrose and inulin in the presence of citric acid,93 and sucrose in the presence of acetic94 acid, yields caramels containing, among other products, di-D-fructose dianhydrides and glycosylated difructose dianhydrides, as described in Section V.6). Similarly, the thermal treatment of 6-0-ot-D-glu-copyranosyl-D-fructofuranose (palatinose) in the presence of citric acid87 has been shown to produce appreciable proportions of glucosylated di-D-fructose dianhydrides. 

Di-D-fructose dianhydrides have resulted from the thermal activation of inulin95 and fructose,96 as described in section VI3. 

Di-D-fructose dianhydrides have also been isolated" from commercial chicory, which is used as an additive for coffee or in coffee substitutes. Chicory is obtained by roasting the roots of chicory (Cichorium sp.), a member of the Compositae, which contains inulin (in its roots) as a storage polysaccharide. 

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 non-precipitable (that is, lower molecular weight) component of a product from thermolysis (170°C, 80 min.) of anhydrous amorphous sucrose acidified with 1% citric acid contains 19% disaccharides, predominantly di-D-fructose dianhydrides.93 Only two of these were identified, namely a-D-Fru/-1,2 2,1 - 3-D-Fru/ (5) and ct-D-Fru/-l,2 2,1 - 3-D-Frup (1) in the ratio 1 1. This result can be compared with the ratio 2 1 for the commercial caramel.94... 

These results indicate that, during thermolyses of fructose-containing saccharides, di-D-fructose dianhydrides are formed readily, but subsequent isomerization is extremely slow—even in the presence of added acid. However, under these conditions, the protonating power of any acid is moot. At the high temperatures used, residual water would be driven off rapidly, unless the reaction vessel is pressurized therefore, reaction occurs in the anhydrous melt. It is presumably protonation of one of the ring oxygen atoms in the dianhydrides that constitutes the first step in isomerization, followed by scission of a C-O bond to yield one of the oxocarbenium ion intermediates postulated in Refs. 31 and 80. Such ions have also been postulated as intermediates in the isomerization of spiroketals to a more-stable product. This latter isomerization can be extremely facile 104 dilute aqueous acid,120 or non-aqueous Lewis-acid conditions121 have been used to effect such transformations. 

VIII. Uses of Di-d-fructose Dianhydrides 1. Di-D-fructose Dianhydrides and Nutrition... 

In 1993, the di-D-fructose dianhydrides were summarized as being of little, if any, commercial importance. 73 However, a search of the literature reveals an appreciable number of patents issued since 1989 for the manufacture of these compounds. These include enzymic methods for the production of individual dianhydrides (Ref. 130) or methods of production of mixtures using anhydrous HF or pyridinium poly(hydrogen fluoride) (see Ref. 131). Most cite the di-D-fructose dianhydrides as low-calorie sweetening agents (Ref. 132), and some claim anti-cariogenic properties (Refs. 132 and 133). 

Di-D-fructose dianhydrides have been claimed to promote the growth of bifidobacteria in vitro.134 Bifidobacterium spp. are found in the large intestines of most vertebrates.135 The benefits attributed to the presence of a healthy population of bifidobacteria in the gut include inhibition of carcinogenesis,136 suppression of putrefactive substances,137 lowering of blood pressure and blood... 

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... 

Optical Rotations and Melting Points of Di-D-fructose Dianhydride Derivatives and Their Per-0-acetates... 

C NMR Spectra of the Fructose Components in Di-D-fructose Dianhydride Derivatives... 

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