Difructose Dianhydrides Research Articles

Hydrolysis of Sucrose over Sulfonic Acid Resins

AbstractSucrose hydrolysis on acidic ion‐exchange resins is a long‐established process in the sugar industry, but the formation of side products is less understood. A resin typically used in the industrial process (C124SH, Purolite) was investigated in a broad range of sucrose concentration (7 to 75 % w/w) and temperatures from 25 to 80 °C. Fructose is converted to 5‐hydroxymethylfurfural (HMF) due to a 1/2 order reaction. This is explained by the formation of a fructose disaccharide (monoanhydride) as an intermediate decomposing to HMF and fructose. Difructose dianhydrides (DFAs) are separately formed as prevailing by‐products. The color of the product mixture is correlated to HMF and found to be reduced by size exclusion inside the resins. Diffusional limitations of the total reaction are investigated by comparison of the entire resin bead with its size‐reduced forms obtained by milling. Without diffusion limitation the catalytic activity increases with the sugar concentration while the diffusion control leads to a maximal activity around 40 % w/w sugar. Diffusion coefficients of sucrose are calculated.

Adsorption of difructose dianhydrides on hydrophobic Y-zeolites

The chemical conversion of fructose to a mixture of isomeric difructose dianhydrides (DFAs) is limited by thermodynamical reason, and the enzymatic production of DFAIII from inulin is restricted by the yield of the final crystallization. Both processes require a separation process for the isolation of pure samples. Hydrophobic Y-zeolites are shown here to adsorb DFAs from aqueous solution. The interaction of the zeolite with DFAs is significantly greater than the interaction with fructose and higher fructose containing oligosaccharides and varies with the structure of the DFA isomer, the β,β-(1-2':2-1′)-connected difructopyranose dianhydride having an exceptional high affinity. Compared to sucrose the DFA adsorption is significantly slower. Molecular modeling of the DFAs by ab initio (GTO 3-31G*) and MM+ force field revealed a stiff but stretched geometry which enables the molecules to enter the 0.74 nm pore openings without great conformational change. An application of the DFA adsorption was realized for isolating biotechnologically produced DFA III. DFA III can be selectively adsorbed from the residue after its crystallization and desorbed with ethanol. The application of the method to the isolation of DFAs from a mixture of 13 isomers, obtained by chemical condensation of fructose, yields a preferential sorption of 2 DFA isomers. • DFA adsorption by hydrophobic interaction. • Much greater adsorption compared to fructose. • Cylindrical carbohydrate conformation. • Molecular diameter matches pore opening.

A comparison of fast and reactive pyrolysis with insitu derivatisation of fructose, inulin and Jerusalem artichoke (Helianthus tuberosus)

Reactive pyrolysis is a technique that provides mechanistic information by performing pyrolysis of the substrate in a sealed glass capsule at elevated temperature and pressure for relatively long time. This technique has already shown great potential for the analysis of biomass, favouring the formation of only the most thermostable compounds. In this work, both fast and reactive pyrolysis with on-line gas chromatography-mass spectrometry analysis (Py-GC/MS) are used to study fructose, inulin and Jerusalem artichoke tubers (Heliantus tuberosus). Interesting differences were found between the two systems, and became even more evident as the reaction time was increased. The most striking result was the formation of di-fructose dianhydrides (DFAs), a class of compounds with interesting biological activities. DFAs were obtained in high yields from reactive pyrolysis, but not from fast pyrolysis. Hypotheses on the pyrolysis mechanisms were made based upon the composition of the pyrolysates. This work describes for the first time the behaviour of fructans under reactive pyrolysis.

Carbon Dioxide as a Traceless Caramelization Promotor: Preparation of Prebiotic Difructose Dianhydrides (DFAs)-Enriched Caramels from d-Fructose.

Activation of a concentrated solution of d-fructose with carbonic acid, generated from carbon dioxide, induces the formation of difructose dianhydrides (DFAs) and their glycosylated derivatives (glycosyl-DFAs), a family of prebiotic oligosaccharides. Under optimized conditions, up to 70% of the active DFA species were obtained from a highly concentrated solution of fructose, avoiding the filtration step and contamination risk associated with the current procedures that employ heterogeneous catalysis with acid ion-exchange resins. The optimized CO2-promoted preparation of DFA-enriched caramel described here has been already successfully scaled up to 150 kg of d-fructose for nutritional studies, showing that implementation of this process is possible at a larger scale.

Fructose and inulin: Behaviour under analytical pyrolysis

EGA-MS (evolved gas analysis–mass spectrometry) and Py(HMDS)-GC/MS (pyrolysis-gas chromatography coupled with mass spectrometry with in situ derivatisation using hexamethyldisilazane as a silylating agent) were used to study the behaviour under pyrolytic conditions of fructose, inulin and topinambour (Jerusalem artichoke), a tuber, in which inulin coexists with other organic and inorganic species. The aim was to acquire a complete picture of the chemical characteristics and reactivity of fructose and its polymers (fructans). In fact, fructans constitute the reserve carbohydrates of several botanical species and are important substrates for obtaining high value-added products.EGA-MS of inulin and topinambour provided information on their different thermal and chemical complexities. Despite tuber being constituted mostly by inulin, its thermogram was much more complex than obtained for inulin alone. The EGA curve of topinambour extended for a wider temperature range and provided mass spectra containing several peaks related to the fragmentation of compounds different from those obtained in the analysis of inulin. The evolution of levoglucosan clearly indicates the presence of glucose units in the tuber. The pyrolysis of fructose and inulin carried out by Py-GC/MS generated a high number of pyrolysis products, the main ones being dihydroxyacetone, 5-hydroxymethyl-2-furaldehyde, and 2,6-anhydrofructofuranose. The similarity between the two pyrograms suggests that under pyrolysis conditions, one of the first reactions of inulin is the cleavage of the glycosidic bond. An important difference was obtained in the pyrolysis of inulin alone, which led to the formation of di-fructose dianhydrides. A different quali-quantitative distribution of the pyrolysis products was obtained for topinambour likely due to the different monosaccharides in the topinambour composition from fructose, as well as to the presence of significant amounts of inorganics.

From fructans to difructose dianhydrides.

Fructans are the polymers of fructose molecules, normally having a sucrose unit at what would otherwise be the reducing terminus. Inulin and levan are two basic types of simple fructan, which contain β-(2, 1) and β-(2, 6) fructosyl-fructose linkage, respectively. Fructans not only can serve as soluble dietary fibers for food industry, but also may be biologically converted into high-value products, especially high-fructose syrup and fructo-oligosaccharides. In recent years, much attention has been focused on production of difructose dianhydrides (DFAs) from fructans. DFAs are cyclic disaccharides consisting of two fructose units with formation of two reciprocal glycosidic linkages. They are expected to have promising properties and beneficial effects on human health. DFAs can be produced from fructans by fructan fructotransferases. Inulin fructotransferase (IFTase) (DFA III-forming) and IFTase (DFA I-forming) catalyze the DFA III and DFA I production from inulin, respectively, and levan fructotransferase (LFTase) (DFA IV-forming) catalyzes the production of DFA IV from levan. In this article, the DFA-producing microorganisms are summarized, relevant studies on various DFAs-producing enzymes are reviewed, and especially, the comparisons of the enzymes are presented in detail.

Microwave-assisted synthesis of prebiotic di-D-fructose dianhydride-enriched caramels.

The synthesis of prebiotic caramels involving the use of microwaves as the activating/heating source has been achieved. The yields in di-fructose dianhydrides (DFAs) in caramels were measured. The aim of this study was twofold: first to check the feasibility of the process, and second to determine the conditions to obtain an optimum response with microwave heating. The study showed that it was possible to obtain a yield of almost 50% of DFAs in a reaction time that was 10 times shorter than a previous study; i.e. 5-10 min for microwave activation compared to 60-120 min for conventional heating. It was shown that the radiation time and the radiation power were linked. The simultaneous determination of the values of these two factors was therefore necessary to obtain significant yields. This technique demonstrates the advantage of activation for mixtures such as caramels.

PREBIOTIC DI‐D‐FRUCTOSE DIANHYDRIDE‐ENRICHED CARAMELS: DEVELOPMENT OF BATCH PROCESS (1 L) AND OPTIMIZATION OF OPERATING CONDITIONS

ABSTRACTAn experimental design was used to scale up the synthesis of caramels enriched in di‐D‐fructose dianhydride. The scale‐up from 100 mL to 1 L is particularly difficult because the mixture is a viscous paste. Using the Doehlert design for three factors, a model of difructose dianhydrides (DFAs) yield in relation to operating conditions was established. By considering only the significant coefficients, a second model was rewritten. The second model was verified and validated. F‐test was calculated (3.3) and was satisfactory (probability of adjustment is 25%). In a 100‐mL flask, the optimum DFAs yield was 30%. The determination of an optimum in a 1‐L reactor was 50% with better rheological conditions (a lower proportion of resin and a higher proportion of water).PRACTICAL APPLICATIONSDFAs have prebiotic properties and are intended to be used as food additives. The possibility of producing them by caramelization allows one to consider the addition of these healthy caramels to different food matrices. The synthesis used at 100‐mL scale presented the advantage of satisfying yields but the inconvenience of strong rheological constraints. This work shows that the passage at the larger scale is possible while increasing performance and decreasing the viscosity of the medium. This step is fundamental in the industrial extrapolation process.

Stereoselective Synthesis of Difructose Dianhydrides by Use of the Xylylene Group as Stereodirecting Element in Spiroketalisation Reactions

AbstractThe use of the o‐xylylene protecting group as an element of remote stereochemical control in bis(spiroketalisation) reactions of D‐fructose has been investigated. The presence of the cyclic diether functionality favours the trans‐diequatorial disposition of oxygen substituents, a conformational arrangement that is encountered in the 3‐O/4‐O segment in β‐D‐fructopyranoside and β‐D‐fructofuranoside moieties in di‐D‐fructose dianhydrides (DFAs). Moreover, the presence of the o‐xylylene group in cis‐oriented vic‐diol segments slows down the interconversion rate between the two chair conformers in fructopyranose rings, which has a strong influence on the stereochemical outcome of the dimerisation reaction. Those features have been exploited to develop stereoselective syntheses of dipyranose and difuranose DFAs with the aid of triflic acid activation of 1,2‐O‐isopropylidene‐D‐fructose precursors. For difuranose DFAs, the combination of this strategy with the concept of rigid spacer‐mediated intramolecular spiroketalisation, with use of xylylene‐tethered D‐fructose precursors, further allows double stereocontrol. The conclusions of this study open new perspectives in the stereoselective synthesis of complex spiroketal derivatives in general and in the preparation of pure DFA standards with application in food chemistry in particular.

Di-d-fructose Dianhydride-Enriched Caramels: Effect on Colon Microbiota, Inflammation, and Tissue Damage in Trinitrobenzenesulfonic Acid-Induced Colitic Rats

In the present study we describe the preparation and chemical characterization of a caramel with a high (70%) content of difructose dianhydrides (DFAs) and glycosylated derivatives (DFAs). This product was obtained by thermal activation (90 degrees C) of highly concentrated (90% w/v) aqueous D-fructose solutions using the sulfonic acid ion-exchange resin Lewatit S2328 as caramelization catalyst. DFAs represent a unique family of cyclic fructans with prebiotic properties already present in low proportions (<15%) in commercial caramel. We report the antiinflammatory activity of the new DFA-enriched caramel in the trinitrobenzenesulfonic acid (TNBS) model of rat colitis, an experimental model that resembles human inflammatory bowel disease (IBD), and compare its effects with those obtained with a commercial sucrose caramel and with linear fructooligosaccharides (FOS). For this purpose, the effects on colon tissue damage, gut microbiota, short-chain fatty acid (SCFAs) production, and different inflammatory markers were evaluated. The administration of DFA-enriched caramel to colitic rats showed intestinal antiinflammatory effect, as evidenced macroscopically by a significant reduction in the extent of the colonic damage induced by TNBS. This effect was similar to that obtained with FOS in the same experimental settings, whereas commercial caramel was devoid of any significant antiinflammatory effect. The beneficial effect was associated with the inhibition of the colonic levels of the proinflammatory cytokines, tumor necrosis factor alpha (TNF alpha) and interleukin 1beta (IL-1beta), and the reduction in colonic myeloperoxidase (MPO) activity and inducible nitric oxide synthase (iNOS) expression. The DFA-enriched caramel also promoted a more favorable intestinal microbiota, increasing lactobacilli and bifidobacteria counts as well as inducing higher concentrations of SCFAs in the luminal colonic contents. These results reinforce the concept of DFAs and glycosyl-DFAs as dietary beneficial compounds with prebiotic properties and suggest that the novel DFA-enriched caramel here reported may be an interesting candidate to be explored for the dietary treatment of human IBD.

Hydrolytic Methods for the Quantification of Fructose Equivalents in Herbaceous Biomass

A low, but significant, fraction of the carbohydrate portion of herbaceous biomass may be composed of fructose/fructosyl-containing components ("fructose equivalents"); such carbohydrates include sucrose, fructooligosaccharides, and fructans. Standard methods used for the quantification of structural-carbohydrate-derived neutral monosaccharide equivalents in biomass are not particularly well suited for the quantification of fructose equivalents due to the inherent instability of fructose in conditions commonly used for hemicellulose/cellulose hydrolysis (>80% degradation of fructose standards treated at 4% sulfuric acid, 121 degrees C, 1 h). Alternative time, temperature, and acid concentration combinations for fructan hydrolysis were considered using model fructans (inulin, beta-2,1, and levan, beta-2,6) and a grass seed straw (tall fescue, Festuca arundinacea) as representative feedstocks. The instability of fructose, relative to glucose and xylose, at higher acid/temperature combinations is demonstrated, all rates of fructose degradation being acid and temperature dependent. Fructans are shown to be completely hydrolyzed at acid concentrations well below that used for the structural carbohydrates, as low as 0.2%, at 121 degrees C for 1 h. Lower temperatures are also shown to be effective, with corresponding adjustments in acid concentration and time. Thus, fructans can be effectively hydrolyzed under conditions where fructose degradation is maintained below 10%. Hydrolysis of the beta-2,1 fructans at temperatures > or =50 degrees C, at all conditions consistent with complete hydrolysis, appears to generate difructose dianhydrides. These same compounds were not detected upon hydrolysis of levan, sucrose, or straw components. It is suggested that fructan hydrolysis conditions be chosen such that hydrolysis goes to completion; fructose degradation is minimized, and difructose dianhydride production is accounted for.

Stereoselective synthesis of nonsymmetrical difructose dianhydrides from xylylene-tethered d-fructose precursors

Nonsymmetrical furanose–pyranose difructose dianhydrides (DFAs), a class of cyclic disaccharides present in foodstuffs, have been prepared in high yield by connecting the reacting monosaccharide moieties through a xylylene bridge prior to triflic acid-promoted bis-spiroketalization. The reaction can then proceed either intra- or intermolecularly, both the regio- and the stereoselectivity being strongly dependent on the spacer length. Noteworthy, the longer m- and p-xylylene positional isomers led to the thermodynamic α- d-fructofuranose β- d-fructopyranose 1,2′:2,1′-dyanhydride 1, the major DFA in commercial caramel, in a stereoselective manner. The shorter o-xylylene tether afforded preferentially the elusive contra-thermodynamic β- d-fructofuranose α- d-fructopyranose diastereomer 2, a trace constituent of caramel. The results have been rationalized in terms of stereoelectronic and conformational properties and offer new perspectives for the preparation of pure DFA standards for analytical and nutritional studies.

Structural and Functional Insights into Intramolecular Fructosyl Transfer by Inulin Fructotransferase

Inulin fructotransferase (IFTase), a member of glycoside hydrolase family 91, catalyzes depolymerization of beta-2,1-fructans inulin by successively removing the terminal difructosaccharide units as cyclic anhydrides via intramolecular fructosyl transfer. The crystal structures of IFTase and its substrate-bound complex reveal that IFTase is a trimeric enzyme, and each monomer folds into a right-handed parallel beta-helix. Despite variation in the number and conformation of its beta-strands, the IFTase beta-helix has a structure that is largely reminiscent of other beta-helix structures but is unprecedented in that trimerization is a prerequisite for catalytic activity, and the active site is located at the monomer-monomer interface. Results from crystallographic studies and site-directed mutagenesis provide a structural basis for the exolytic-type activity of IFTase and a functional resemblance to inverting-type glycosyltransferases.

Spacer-Mediated Synthesis of Contra-Thermodynamic Spiroacetals: Stereoselective Synthesis of C2-Symmetric Difructose Dianhydrides

The xylylene moiety (ortho, meta, and para) was employed as a rigid tether in the spacer-mediated synthesis of difructose dianhydrides (DFAs), a unique class of bis-spiroacetal derivatives present in food products. The synthetic methodology exploits the suitability of triflic acid to promote spirocyclization in organic solvents under irreversible reaction conditions, using anomeric isopropylidene fructose derivatives as precursors. Advantage was taken of the strong dependence of the conformational properties of DFAs on the relative configuration of the spiroketal centers. Highly stereoselective syntheses of the contra-thermodynamic difructofuranose and difructopyranose diastereomers, namely the C2-symmetric derivatives having the beta-configuration at both anomeric centers, have been accomplished by judicious choice of the xylylene positional isomer and of the linking position to the fructose building blocks. Interestingly, the rigid spacer concept has also been implemented to favor intermolecular processes leading to higher macrocyclic architectures that incorporate the bis-spiro fructodisaccharide subunit.

ChemInform Abstract: Difructose Dianhydrides as Synthetic Intermediates. A Synthesis of 3,6‐ Anhydro‐keto‐D‐fructose.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Difructose dianhydrides from sucrose and fructo-oligosaccharides and their use as building blocks for the preparation of amphiphiles, liquid crystals, and polymers

Controlled selective protonic activation of the fructosyl moiety in sucrose and fructo-oligosaccharides, with pyridinium poly(hydrogen fluoride) at 20°C, yielded either the kinetic product α- d-fructofuranose β- d-fructofuranose 1,2′:2,1′-dianhydride ( 1), or its thermodynamically more stable isomer α- d- fructofuranose β- d-fructopyranose 1,2′:2,l′-dianhydride ( 2), depending on the hydrogen fluoride-pyridine ratio. A similar reaction was performed with 6,6′-dichloro-6,6′-dideoxysucrose, or 6,6′-dideoxy-6,6′-diiodosucrose, using a slightly higher ratio of HF, resulting in the corresponding 6-deoxy-6-halo-α- d-fructofuranose 6′-deoxy-6′- halo-β- d-fructofuranose 1,2′:2,1′-dianhydride derivatives. Both 6,6′-dihalides were converted, upon action of the appropriate nucleophile, into the difructofuranose dianhydride derivatives bearing the 6,6′-di- S-heptyl-6,6′-dithio, 6,6′-diazido-6,6′-dideoxy and then 6,6′-diamino-6,6′-dideoxy functionalities. 6-Chloro-6-deoxy and 6-deoxy-6-iodo derivatives of 2 were also prepared by direct halogenation, and further converted into the 6- S-heptyl-thio, 6-azido-6-deoxy and then 6-amino-6-deoxy derivatives of 2. Reaction of chloromethyloxirane with 1 or 2 yielded hydrophilic polymers. The 6,6′-di- S-heptyl-6,6′-dithio derivative of 1 displayed liquid crystal properties. The 6,6′-dideoxy-6,6′-diiodosucrose precursor was prepared by the reaction of Garegg's iodine-imidazole-triphenylphosphine reagent with sucrose in N,N-dimethylformamide solution.

Protonic reactivity of sucrose in anhydrous hydrogen fluoride

Sucrose reacts quantitatively, when dissolved at high concentration in anhydrous hydrogen fluoride, to afford a complex mixture of difructose dianhydrides and their glucosylated derivatives. Oligo- and small poly-saccharides up to dp 14 were detected by FABMS. Oligosaccharides up to dp 4, representing ≈50% of the total mixture, have been isolated and characterized by mass spectrometry, 13C NMR spectroscopy, and comparison with reference oligosaccharides previously obtained by unambiguous synthesis, α- d-Fructofuranose β- d-fructopyranose 1,2′:2,1′-dianhydride is the main spirodioxanyl pseudodisaccharide entity found in the mixture, either free or glucosylated at C-6 and to a lesser extent at C-3, C-4, C-4′ C-6, and C-5′ C-6. Minor spirodioxanyl pseudodisaccharide components are di-β- d-fructopyranose 1,2′:2,1′-dianhydride, which has also been found glucosylated at C-5, α- d-fructopyranose β- d-fructopyranose 1,2′:2,1′-dianhydride, β- d-fructofuranose β- d-fructopyranose 1,2′:2,3′-dianhydride, and the 6,6′-diglucosylated α- d-fructofuranose β- d-fructofuranose 1,2′:2,1′-dianhydride. A 13C NMR examination of the higher mass oligomeric fraction fraction suggests that it may involve 6- O-isomaltooligoglycosyl α- d-fructofuranose β- d-fructopyranose 1,2′:2,1′-dianhydride as the main structural components. The reaction of sucrose in anhydrous HF is believed to proceed through initial selective protonic activation of the tertiary anomeric carbon atom of the fructose moiety, resulting in the quantitative formation of difructose dianhydrides, which subsequently suffer electrophilic substitution by glucopyranosyl oxocarbenium ions generated in a second step by action of the HF.

Selective protonic activation of isomeric glycosylfructoseswith pyridinium poly(hydrogen fluoride) and synthesis of spirodioxanyl oligosaccharides

Selective activation of the ketose unit in the isomeric glycosylfructoses, palatinose, leucrose,maltulose, turanose and lactulose, with pyridinium poly(hydrogen fluoride) resulted in the almost quantitative formation of glycosylated difructose dianhydrides. The reaction preferentially involves a reactive fructofuranosyl oxocarbenium ion and is subject to stereoelectronic control. The relative amounts of isomeric spirodioxanyl oligosaccharides obtained within a series was shown to depend on the reaction conditions, especially on the hydrogen fluoride-pyridine ratio. Using suitable concentrations of hydrogen fluoride in pyridine, the reaction was easily directed to the formation of the kinetic difuranosyl or thermodynamic pyranosyl derivatives. More rigorous conditions resulted in the specific hydrolysis of one glycosidic bond in the tetrasaccharides derived from palatinose, leucrose and turanose, to yield spirodioxanyl trisaccharides.

Complexes of carbohydrates with metal cations. XVI•Di-D-fructose and di-L-sorbose dianhydrides

Di-D-fructose 2′, 1:2,1′-dianhydrides form complexes with metal cations if the two anomeric carbon atoms have the same configuration. Such anomers have the central 1,4-dioxane ring in a flexible form; complex formation involves O-1, O-1′, O-3, and O-3′, as confirmed by the X-ray crystal structure of the strontium complex of the β,β-dipyranose anomer. The α,β-anomers, and dianhydrides containing only furanose rings, do not form such complexes. Keywords: difructose dianhydrides, complex formation with cations, crystal structure of complex, chromatographic separation on ion-exchange resins.

Kinetics of Difructose Dianhydrides Formation under Fructose Crystallization Conditions

AbstractFructose undergoes dehydration reactions to form difructose dianhydrides during crystallization. Difructose dianhydrides can be incorporated into fructose crystals and inhibit the crystal growth. In this study, the kinetics of difructose dianhydrides formation under industrial crystallization conditions were investigated. Four difructose dianhydrides were detected by HPLC analysis. An empirical second‐order irreversible kinetic model was proposed for the reaction. The extent of reaction increased with increasing temperature and decreasing pH value of the solution. The amount of two of the difructose dianhydrides stopped increasing when the fructose concentration was about 70% or less. On the other hand, the formation of all dimers were retarded when the initial fructose concentration was higher than 80%.