- NMR Detection of Simultaneous Formation of [2]- and [3]Pseudorotaxanes in Aqueous Solution between α-Cyclodextrin and Linear Aliphatic α,ω-Amino acids, an α,ω-Diamine and an α,ω-Diacid of Similar Length, and Comparison with the Solid-State Structures
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The interactions of 11-aminoundecanoic acid (1), 12-aminododecanoic acid (2), 1,12-diaminododecane (3), and 1,13-tridecanoic diacid (4) with α-cyclodextrin (αCD) were studied in aqueous solution by NMR spectroscopy. The association modes were established with titration and continuous variation plots, variable temperature NMR spectra, and dipolar interactions as recorded in 2D ROESY spectra. The studies were carried out at pH 7.3 and 13.6. These long, linear bifunctional molecules were found to form simultaneously [2]- and [3]pseudorotaxanes with αCD in the aqueous solution. At the higher pH the 1:1 adducts were present at concentrations higher than at the neutral pH. The longer guests formed complexes enriched in the 2:1 constituent at both pH values. There were clear indications that the [2]pseudorotaxanes are present in two isomeric forms. The presence of isomers also in the [3]pseudorotaxanes was not ruled out. Various exchange rate regimes were observed; clearly in neutral solutions the formation of the 1:1 complexes was fast in the NMR time scale, whereas the threading of a second αCD ring was a slower process. In the solid state, the adduct of αCD/2 had the structure of a [3]pseudorotaxane, in accordance with previously solved crystal structures of αCD/3 and βCD/4. The species in solution, in contrast with those present in the solid state, are therefore of varying nature, and thus the frequently and conveniently assumed 1:1 stoichiometry in similar systems is an oversimplification of the real situation.
- Eliadou, Kyriaki,Yannakopoulou, Konstantina,Rontoyianni, Aliki,Mavridis, Irene M.
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- Solid state polycondensation within cyclodextrin channels leading to watersoluble polyamide rotaxanes
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α,ω-Aminocarboxylic acids form microcrystalline inclusion compounds with α-cyclodextrin. In these inclusion compounds cyclodextrins build up channel structures, in which the α,ω-aminocarboxylic acids can be polycondensed at 200-240°C. As the resulting pol
- Wenz, Gerhard,Steinbrunn, Marc Boris,Landfester, Katharina
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- Thermodynamic and nuclear magnetic resonance study of the reactions of α- and β-cyclodextrin with acids, aliphatic amines, and cyclic alcohols
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Titration calorimetry was used to determine equilibrium constants and standard molar enthalpy, Gibbs energy, and entropy changes for the reactions of a series of acids, amines, and cyclic alcohols with α- and β-cyclodextrin. The results have been examined in terms of structural features in the ligands such as the number of alkyl groups, the charge number, the presence of a double bond, branching, and the presence of methyl and methoxy groups. The values of thermodynamic quantities, in particular the standard molar Gibbs energy, correlate well with the structural features in the ligands. These structural correlations can be used for the estimation of thermodynamic quantities for related reactions. Enthalpy-entropy compensation is evident when the individual classes of substances studied herein are considered, but does not hold when these various classes of ligands are considered collectively. The NMR results indicate that the mode of accommodation of the acids and amines in the α-cyclodextrin cavity is very similar, but that the 1-methyl groups in 1-methylhexylamine and in 1-methylheptylamine and the N-methyl group in N-methylhexylamine lie outside the α-cyclodextrin cavity. This latter finding is consistent with the calorimetric results. Many of the thermodynamic and NMR results can be qualitatively understood in terms of van der Waals forces and hydrophobic effects.
- Rekharsky, Mikhail V.,Mayhew, Martin P.,Goldberg, Robert N.,Ross, Philip D.,Yamashoji, Yuko,Inoue, Yoshihisa
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- Kinetics of the self-assembly of α-cyclodextrin [2]pseudorotaxanes with 1,12-bis(4-(α-alkyl-α-methylmethanol)pyridinium)dodecane dications in aqueous solution
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The kinetics and thermodynamics of the self-assembly of a series of [2]pseudorotaxanes comprised of α-cyclodextrin (α-CD) and racemic 1,12- bis(4-(α-alkyl-α-methylmethanol)pyridinium)dodecane dications (L(CH2)12L2+) in aqueous solutions have been investigated using 1H NMR spectroscopy. The mechanism of assembly involves inclusion of the α-methyl- α-alkylmethanol substituent groups (-C(CH3)(OH)R, where R = Me, Et, Pr, Bu, allyl, and 4-butenyl) by α-CD, followed by a rate-determining passage of the cyclodextrin over the pyridinium group onto the dodecamethylene chain. Dicationic threads containing end groups with R = Ph or i-Pr or where L = 4- (α,α-diethylmethanol)-pyridinium did not form α-cyclodextrin pseudorotaxanes, even after prolonged heating. The trends in the rate and activation parameters may be related to the size, shape, and hydrophobicity of the alkyl substituents and are compared with several other systems from the literature. An increase in the length and hydrophobicity of the alkyl group increases the strength of end group inclusion and decreases the rate of threading. In addition, the presence of unsaturation in the alkyl substituent (allyl vs propyl and 4-butenyl vs butyl) results in an increase in the threading rate constant.
- Smith, A. Catherine,Macartney, Donal H.
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- Volume Change on Complex Formation Between Anions and Cyclodextrins in Aqueous Solution
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Partial molal volume changes during complex formation between SCN(1-), I(1-), and ClO4(1-) and α- and β-cyclodextrin have been determined by two independent methods of measurements; one based on density measurement and subsequent calculation of apparent molal volumes, the other on differentiating the association constants with respect to pressure.Results from the two methods are in good agreement.Negative volume changes were observed for complex formation between the anions and α-cyclodextrin while zero or slightly positive values were observed for complex formation with β-cyclodextrin.The result is consistent with the idea that the anions do not become dehydrated as they form complexes with cyclodextrins.
- Hoeiland, H.,Hald, L.H.,Kvammen, O.J.
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- Retardation of acetal hydrolysis by cyclodextrins and its use in probing cyclodextrin-guest binding
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Hydrolysis of benzaldehyde dimethyl acetal 1 in aqueous acid is slowed down greatly by cyclodextrins (SDs): α-CD, β-CD, hp-β-CD (hydroxypropyl-β-cyclodextrin) and γ-CD. The variations of the observed first-order rate constants (Kobs) with [CD] exhibit saturation behaviour consistent with 1:1 binding between 1 and the CDs. In the case of β-CD and hp-β-CD, the binding is relatively strong and the CD-bound acetal is unreactive. In contrast, binding of the acetal by α-CD and γ-CD is much weaker, but only with α-CD does the CD-bound form show significant reactivity. The four CD-mediated reaction, have been evaluated as probe reactions for determining dissociation constants of {CD-'guest'} complexes. In this approach, added guests attenuate the retarding effect of CD-substrate binding and cause an increase in the rate of acetal hydrolysis. The method works well for alipharic alcohols and ketones binding to β-CD and hp-β-CD, but it is less successful with α-CD because of the shallow dependence of kobs on [α-CD] in the probe action. With γ-CD, the approach is not applicable at all, because added guests cause a further reduction in the rate of acetal hydrolysis, not an increase. Various implications of these findings are discussed.
- Tee, Oswald S.,Fedortchenko, Alexei A.,Soo, Patrick Lim
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- Catalysis of ester aminolysis by cyclodextrins. The reaction of alkylamines with p-nitrophenyl alkanoates
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The effects of four cyclodextrins (α-CD, β-CD, hydroxypropyl-β-CD, and γ-CD) on the aminolysis of p-nitrophenyl alkanoates (acetate to heptanoate) by primary amines (n-propyl to n-octyl, isobutyl, isopentyl, cyclopentyl, cyclohexyl, benzyl) in aqueous solution have been investigated. Rate constants for amine attack on the free and CD-bound esters (k(N) and k(cN)) have ratios (k(cN)/k(N)) varying from 0.08 (retardation) to 180 (catalysis). For the kinetically equivalent process of free ester reacting with CD-bound amine (k(Nc)), the ratios k(Nc)/k(N) vary from 0.2 to 28. Either way, there is evidence of catalysis in some cases and retardation in others. Changes in reactivity parameters with structure indicate more than one mode of transition state binding to the CDs. Short esters react with short alkylamines by attack of free amine on the ester bound by its aryl group, but for longer amines, free ester reacts with CD-bound amine. Reaction of long esters with long amines, which is catalyzed by β-CD and γ-CD, involves inclusion of the alkylamino group and possibly the ester acyl group. The larger cavity of γ-CD may allow the inclusion of the ester aryl group, as well as the alkylamino group, in the transition state. Reaction between an ester bound to the CD by its acyl group and free amine appears not to be important.
- Gadosy,Boyd,Tee
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- Altered product specificity of a cyclodextrin glycosyltransferase by molecular imprinting with cyclomaltododecaose
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Cyclodextrin glycosyltransferases (CGTases), members of glycoside hydrolase family 13, catalyze the conversion of amylose to cyclodextrins (CDs), circular α-(1,4)-linked glucopyranose oligosaccharides of different ring sizes. The CD containing 12 α-D-gluc
- Kaulpiboon, Jarunee,Pongsawasdi, Piamsook,Zimmermann, Wolfgang
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- Induced circular dichroism and UV-VIS absorption spectroscopy of cyclodextrin inclusion complexes: Structural elucidation of supramolecular azi-adamantane
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The first induced circular dichroism (ICD) analyses of diazirineγyciodextrin inclusion complexes are reported. The stoichiometries and association constants of the guestηost complexes with α-, β-, and γ- cyclodextrin were determined. In addition, with the α-cyclodextrin complex, UV-vis spectroscopy of water-ethanol solutions showed remarkable fine structure, probably indicating that the diazirine experiences a nonpolar microenvironment. These analytical methods provide details about the architecture and nature of these supramolecular carbene precursors.
- Krois, Daniel,Brinker, Udo H.
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- Cyclodextrin Inclusion Complexes of 1-Pyrenebutyrate: The Role of Coinclusion of Amphiphiles
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Several inclusion complexes with various stoichiometries are formed from 1-pyrenebutyrate ion (P) and the different cyclodextrins (α-, β-, and γ-CD).With α- and β-CD, the initially formed 1:1 complexes lead to the formation of 1:2 complexes (P*α2 and P*β2).As P can be only partially included in the small cavity of α-CD, the equilibrium constants for the formation of both complexes of α-CD are about an order of magnitude smaller than those of β-CD.For the same reason, P*β2, to which we assign a "barrel" configuration, is also an order of magnitude more effective than P*α2 in protecting singlet-excited P against quenching by triethanolamine.We had shown earlier that with γ-CD the 1:1 complex (P*γ) dimerizes to a 2:2 complex (P2*γ2), to which we also assigned a barrel configuration.The lack of efficient 1:2 complex formation in this case is attributed to the large size of the "barrel" enclosed by two γ-CD molecules.The extra space next to a single P molecule in such a cavity would have to be filled with water.However, the formation of a 1:2 inclusion complex between P and γ-CD can be induced by the coinclusion of a molecule with a hydrophobic moiety such as sodium hexanesulfonate (X).This replaces the water within the cavity and leads to the formation of P*X*γ2.This complex provides the highest degree of protection against quenching of excited P in these inclusion complexes.
- Herkstroeter, William G.,Martic, Peter A.,Evans, Ted R.,Farid, Samir
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- ENZYMATIC SYNTHESIS OF CYCLODEXTRINS WITH α-GLUCOSYLFLUORIDE AS A SUBSTRATE FOR CYCLODEXTRIN-α(1->4)GLUCOSYLTRANSFERASE
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By use of immobilized cyclodextrin-α(1->4)glucosyltransferase α-glucosylfluoride is transformed in high yield predominantly into cyclodextrins and maltooligomers as side products.
- Treder, Wolfgang,Thiem, Joachim,Schlingmann, Merten
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- Inclusion Complexes of Alcohols with α-Cyclodextrin
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Calorimetric studies of the inclusion complexes of straight and branched alcohols and of diols with alpha-cyclodextrin (α-CD) have been carried out in water solvent.The data suggest that straight and branched chain alcohols enter the cavity of α-CD alkyl
- Spencer, J. N.,DeGarmo, Jarusha,Paul, I. M.,He, Qing,Ke, Xiaoming,et al.
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- Suitability and limitations of methods for characterisation of activity of malto-oligosaccharide-forming amylases
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The suitability and limitations of essential methods and reference substrates used for characterisation of activity of amylolytic enzymes is investigated. Saccharogenic, chromogenic and chromatographic methods are included. The results are discussed in relation to the measurement of reaction rates, determination of action mode and product specificity and the impact on identification and nomenclature of malto-oligosaccharide-forming amylases. An accurate determination of reaction rates using the saccharogenic methods strongly depends on the degree of polymerisation (DP) of the standards used and the hydrolysis products formed by the amylase. Particularly the use of glucose as standard can lead to overestimates due to the differences in the reducing potential of glucose and malto-oligosaccharides. The reliability of the chromogenic methods for determination of action mode depends on the DP of the substrate and the specificity of the amylase. For a characterisation of the starch hydrolysis products and the variation in the DP during hydrolysis, high performance anion-exchange chromatography with pulsed amperometric detection provided a fast and reliable method. A literature survey revealed varying and inconsistent use of nomenclature of malto-oligosaccharide forming amylases. Therefore a systematic approach identifying three main classes of activity is suggested using not only the mode of action and the DP of the major product but also the stage of hydrolysis at which this product is formed. (C) 2000 Elsevier Science Ltd.
- Duedahl-Olesen, Lene,Haastrup Pedersen, Lars,Lambertsen Larsen, Kim
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- Photochemistry of Benzophenone-Cyclodextrin Inclusion Complexes
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The photochemistry of benzophenone aqueous solutions in the presence of cyclodextrins (CDx) has been studied by stationary and pulsed techniques.Quenching of the phosphorescence is the consequence of hydrogen abstraction following the inclusion in the cyclodextrin cavity of the triplet benzophenone.The H-abstraction process has close analogies with the same reaction in micelles.Radical pair decay is controlled by the dimensions of the CDx cavity: intersystem crossing prevails in the presence of β-CDx, radical excit in the presence of α- and γ-CDx.The fate of the escaped radical also depends on the cavity dimensions, as revealed by the photoreduction quantum yields.
- Monti, Sandra,Flamigni, Lucia,Martelli, Alessandro,Bortolus, Pietro
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- Spectroscopic Studies on Exchange Properties in Through-Ring Cyclodextrin Complexes of Carbazole-Viologen Linked Compounds: Effects of Spacer Chain Length
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Analysis of 1H NMR spectra (400 MHz) revealed a novel mode of interaction between cyclodextrin (CD) and carbazole-viologen linked compounds (CACnV), where the spacer chain was consisted of n methylene units (n = 4, 6, 8, 10, and 12).In the case of α-CD, the complexed species lived long enough to afford distinct proton signals, when the spacer chain was relatively long (n >/= 8).As to CAC12V, the equilibrium constant for the 1:1 complex was 4.9 * 104 M-1 at 30 deg C and coalescence temperatures for the proton signals exceeded 100 deg C.Clear NOEs were observedto prove strong interaction between the protons in the CD cavity and the spacer methylene groups of CAC12V.The spacer was concluded to be encased in the cavity of α-CD.In the case of β-CD, essentially the same "through-ring CD complex" was formed.The line shape analysis indicated that the free energies of activation at 70 deg C for complexation and decomplexation were 11.6 and 17.2 kcal/mol, respectively.Activation parameters for the α-CD complexes were evaluated by the rate of disappearance of intramolecular charge-transfer absorption (420 nm) on the addition of α-CD.The free energy of activation for decomplexation was found to exceed 22 kcal/mol in the α-CD complexes for CACnV (n = 8, 10, and 12).The viologen moiety of CACnV was concluded to be the site of entrance for forming "through-ring CD compex", and the large activation energies were ascribed to dehydration of viologen units to go through the CD cavity.
- Yonemura, Hiroaki,Kasahara, Motohiro,Saito, Hide,Nakamura, Hiroshi,Matsuo, Taku
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- Isolation of Paenibacillus illinoisensis that produces cyclodextrin glucanotransferase resistant to organic solvents.
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A bacterium that secreted cyclodextrin glucanotransferase (CGTase) in a medium overlaid with n-hexane was isolated and identified as Paenibacillus illinoisensis strain ST-12 K. The CGTase of the strain was purified from the culture supernatant. The molecular mass was 70 kDa. The enzyme was stable at pH 6 to 10 and active at pH 5.0 to 8.0. The optimum temperature at pH 7.0 was 65 degrees C in the presence of 5 mM CaCl2. The enzyme produced mainly beta-cyclodextrin. The total yield of alpha-, beta-, and gamma- cyclodextrins was increased 1.4-fold by the addition of ethanol. In particular, the yield of beta-cyclodextrins in the presence of 10% (vol/vol) ethanol was 1.6-fold that without ethanol. The CGTase was stable and active in the presence of large amounts of various organic solvents.
- Doukyu, Noriyuki,Kuwahara, Hirokazu,Aono, Rikizo
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- Synthesis of a Cyclodextrin Heterodimer Having α- and β-Cyclodextrin Units and Its Cooperative and Site-Specific Binding
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A cyclodextrin heterodimer, which has α- and β-cyclodextrin units as two different receptor sites, was prepared.It showed cooperative and site-specific binding to isoamyl p-dimethylaminobenzoate with the alkyl group included in the β-cyclodextrin cavity while dimethylaminobenzene moiety partially included in the α-cyclodextrin cavity.This binding mode was substantiated by the fact that the TICT emission of this guest is greatly enhanced by the cyclodextrin heterodimer.
- Wang, Yong,Ueno, Akihiko,Toda, Fujio
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- Enzyme-mediated dynamic combinatorial chemistry allows out-of-equilibrium template-directed synthesis of macrocyclic oligosaccharides
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We show that the outcome of enzymatic reactions can be manipulated and controlled by using artificial template molecules to direct the self-assembly of specific products in an enzyme-mediated dynamic system. Specifically, we utilize a glycosyltransferase to generate a complex dynamic mixture of interconverting linear and macrocyclic α-1,4-d-glucans (cyclodextrins). We find that the native cyclodextrins (α, β and γ) are formed out-of-equilibrium as part of a kinetically trapped subsystem, that surprisingly operates transiently like a Dynamic Combinatorial Library (DCL) under thermodynamic control. By addition of different templates, we can promote the synthesis of each of the native cyclodextrins with 89-99% selectivity, or alternatively, we can amplify the synthesis of unusual large-ring cyclodextrins (δ and ?) with 9 and 10 glucose units per macrocycle. In the absence of templates, the transient DCL lasts less than a day, and cyclodextrins convert rapidly to short maltooligosaccharides. Templates stabilize the kinetically trapped subsystem enabling robust selective synthesis of cyclodextrins, as demonstrated by the high-yielding sequential interconversion of cyclodextrins in a single reaction vessel. Our results show that given the right balance between thermodynamic and kinetic control, templates can direct out-of-equilibrium self-assembly, and be used to manipulate enzymatic transformations to favor specific and/or alternative products to those selected in Nature.
- Larsen, Dennis,Beeren, Sophie R.
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p. 9981 - 9987
(2019/11/14)
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- Selective synthesis of a [3]rotaxane consisting of size-complementary components and its stepwise deslippage
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An α-cyclodextrin-based size-complementary [3]rotaxane with an alkylene axle was selectively synthesized in one pot via an end-capping reaction with 2-bromophenyl isocyanate in water. Thermal degradation of the [3]rotaxane product yielded not only the ori
- Akae, Yosuke,Okamura, Hisashi,Koyama, Yasuhito,Arai, Takayuki,Takata, Toshikazu
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supporting information; experimental part
p. 2226 - 2229
(2012/06/30)
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- Coordination-assembly for quantitative construction of bis-branched molecular shuttles
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The development and utilization of a new way to build molecular devices is of importance. To build a novel topology of interlocked molecular systems with a controllable mechanical motion, an axle-like compound comprising azobenzene and alkoxy isophthalate
- Zhu, Liangliang,Lu, Meiqun,Qu, Dahui,Wang, Qiaochun,Tian, He
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scheme or table
p. 4226 - 4233
(2011/07/29)
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- Chemical synthesis of cyclodextrins by using intramolecular glycosylation
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An efficient synthesis of cyclodextrins (CDs) by using the intramolecular glycosylation is demonstrated. α-CD, an α(1→4)linked hexaglucoside, was prepared via a block condensation of three maltose units. A modified key maltose intermediate as a precursor to both glycosyl donor and acceptor components was prepared in 6 steps starting from maltose. All the glycosylation for chain elongation and cyclization of saccharides was carried out after tethering the donor to the acceptor by the phthaloyl bridge to give the desired saccharides in good yields with complete α-selectivity. δ-CD composed of 9 glucose units was synthesized by the same manner from three maltotriose units.
- Wakao, Masahiro,Fukase, Koichi,Kusumoto, Shoichi
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p. 8182 - 8190
(2007/10/03)
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- Rotaxane-encapsulation enhances the stability of an azo dye, in solution and when bonded to cellulose
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A cyclodextrin coat dramatically enhances the stability of an azo dye towards reductive bleaching, oxidative bleaching, and photo-bleaching as is demonstrated by the rotaxane 1. This compound is obtained as single isomer in high yield from the amine-substituted dye and trichlorotriazine in water in the presence of the cyclodextrin.
- Craig, Michael R.,Hutchings, Michael G.,Claridge, Tim D. W.,Anderson, Harry L.
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p. 1071 - 1074
(2007/10/03)
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- Influence of cyclodextrins on the fluorescence of some short and long chain linked flexible bisbenzenes in aqueous solution
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The UV absorption, induced circular dichroism (icd) spectra, steady state and time resolved fluorescence emission of the flexible bisbenzenes 1-4 were obtained in aqueous solution and in presence of α-, β-, and γ-cyclodextrin (CD). Bisbenzenes 1 and 2 in an aqueous environment exhibit a dual emission which is differently affected by the CDs. The long-wavelength emission is quenched by α- and β-CD and enhanced by γ-CD. This is due to the formation of inclusion complexes between the CDs and 1 (2) in the ground state, in agreement with the modifications of the UV spectrum and the appearance of icd signals. On the basis of these effects and of the influence of the CDs on the 1 and 2 lifetimes, the dual emission of these bisbenzenes is attributed to a set of different ground-state conformations.
- Bortolus, Pietro,Monti, Sandra,Smoluch, Miroslawa,Bouas-Laurent, Henri,Desvergne, Jean-Pierre
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p. 1165 - 1171
(2007/10/03)
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- Quantitative estimation of the bitter taste intensity of oxyphenonium bromide reduced by cyclodextrins from electromotive force measurements
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The bitter taste of oxyphenonium bromide, an antiacetylcholine drug, is suppressed by cyclodextrins. The extent of the suppression can be predicted from the electromotive force measurements with an oxyphenonium bromide- selective electrode. The relationship between the bitter taste intensity and the electromotive force holds true, regardless of the kind and concentration of natural and modified cyclodextrins. This result is explicable on the basis of the observation that both the bitter taste and the electric potential are determined by the concentration of free oxyphenonium bromide. Some implications and limitations of the present approach are discussed.
- Funasaki, Noriaki,Kawaguchi, Ryusaku,Ishikawa, Seiji,Hada, Sakae,Neya, Saburo,Katsu, Takashi
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p. 1733 - 1736
(2007/10/03)
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- Kinetics of the self-assembly of α-cyclodextrin [2]pseudorotaxanes with polymethylene threads bearing quaternary ammonium and phosphonium end groups
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The kinetics and mechanism of the formation and dissociation of a series of [2]pseudorotaxanes, comprised of α-cyclodextrin (α-CD) as the cyclic component and the ([Me3N(CH2)(n)NMe3]2+ (n = 8-12), [Me2/sub
- Lyon, Angela P.,Banton, Nicola J.,Macartney, Donal H.
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p. 843 - 850
(2007/10/03)
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- Inclusion effects of cyclomaltohexa- and heptaose (α- and β-cyclodextrins) on the acidities of several phenol derivatives
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By means of spectrophotometry, equilibrium constants for the formation of 1:1 inclusion complexes of cyclomaltohexaose (α-cyclodextrin, α-CD) or cyclomaltoheptaose (β-CD) in aqueous solutions have been evaluated for neutral and anionic species of 3-cyanophenol, 4-cyanophenol, 3-nitrophenol, 4-nitrophenol, 4-bromophenol, and 4-methoxyphenol. Using the equilibrium constants of the neutral and anionic species, pK(a) values have been determined for the phenols bound to the α- and β-CD cavities. These phenols, which are accommodated in the α-CD cavity, have been found to be stronger acids than the free, uncomplexed ones, except for 4-methoxyphenol. On the other hand, 4-cyanophenol, 3-nitrophenol, and 4-methoxyphenol bound to the β-CD cavity are weaker acids than the uncomplexed ones, although,3-cyanophenol, 3-nitrophenol, and 3-bromophenol bound to β-CD show the same trend as those bound to α-CD. The different influences of α- and β-CDs on the pK(a) values are likely due to the difference in the magnitudes of the induced dipole moments of the guest caused by α- and β-CDs; depending on the magnitude of the induced dipole moment, the inclusion complexes are stabilized through the dipole-dipole interaction between the host and guest.
- Hamai, Sanyo,Satoh, Noriko
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p. 229 - 237
(2007/10/03)
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- Dynamic aspects in host-guest interactions. Part 4. Kinetic and 1H NMR evidence for multi-step directional binding in the molecular recognition of some 2-naphthylazophenol guests with α-cyclodextrin
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Detailed solution kinetic and equilibria data in aqueous solution are presented for the molecular recognition by α-cyclodextrin (α-CDx) of structurally different types of 2-naphthylazophenol guest. 1H NMR equilibrium titrations and stopped-flow
- Yoshida, Noboru
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p. 2249 - 2256
(2007/10/03)
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- Capillary Electrophoresis as a Method for Determining Binding Constants: Application to the Binding of Cyclodextrins and Nitrophenolates
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For analytes involved in dynamic aquilibrium processes, capillary electrophoresis is a powerful method of determining binding constants.Equilibrium constants from capillary electrophoresis for the binding of nitrophenolates to α-cyclodextrin show good agreement with literature values obtained using calorimetric and spectroscopic methods, confirming capillary electrophoresis as a viable method.We show that it is imperative to make viscosity corrections, to study the full binding range, and to use an algorithm which calculates the concentration of free cyclodextrin rather than the total cyclodextrin concentration.Binding constants for analytes in a complex mixture can be determined simultaneously.The methods have been applied to 2-, 3-, and 4-nitrophenolates with native and derivatized α- and β-cyclodextrins, and results provide insight into the binding process.Data analysis methods for capillary electrophoresis are also successfully applied to liquid chromatography with the use of the same selector as mobile phase additive.
- Penn, Sharron G.,Bergstroem, Edmund T.,Knights, Ian,Liu, Gaoyuan,Ruddick, Andrew,Goodall, David M.
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p. 3875 - 3880
(2007/10/02)
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- Solvent Effects on Chemical Processes. 2. Binding Constants of Methyl Orange with α-Cyclodextrin in Binary Aqueous-Organic Solvents
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The standard free energy change for complex formation is written as a sum of effects from solvent-solvent interactions (the general medium effect), solvent-solute interactions (the solvation effect), and solute-solute interactions (the intersolute effect)
- Connors, Kenneth A.,Mulski, Michael J.,Andrea Paulson
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p. 1794 - 1798
(2007/10/02)
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- Contrasting Behaviors in the Cleavage of Aryl Alkanoates by α- and β-Cyclodextrins in Basic Aqueous Solution
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The kinetics of ester cleavage of 4-carboxy-2-nitrophenyl alkanoates (C2, C4, C6, C7, C8) in aqueous base containing α- or β-cyclodextrin (α- or β-CD) indicate that for the three longer esters there are processes involving two CD molecules which are quite distinct: with α-CD a 2:1 binding leads to inhibition; with β-CD a second-order process provides catalysis.
- Tee, Oswald S.,Du, Xian-xian
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p. 1837 - 1839
(2007/10/02)
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- TOTAL SYNTHESIS OF CYCLOMALTOHEXAOSE
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Described for the first time is a total synthesis of cyclomaltohexaose, in 0.3percent overall yield, in 21 steps starting from maltose.Maltose was transformed into allyl O-(2,3,6-tri-O-benzyl-α-D-glucopyranosyl)-(1->4)-2,3,6-tri-O-benzyl-β-D-glucopyranosi
- Takahashi, Yukio,Ogawa, Tomoya
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p. 277 - 296
(2007/10/02)
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- ISOLATION AND CHARACTERIZATION OF BRANCHED CYCLODEXTRINS
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Three branched cyclodextrins (CDs) were isolated by high-performance liquid chromatography (l.c.) from the mother liquors of a large-scale preparation of the unbranched CDs with Bacillus ohbensis cyclomaltodextrin glucanotransferase.Evidence from chromatographic behavior on three l.c. coloumns of different separation modes, fragmentation analysis, 13C-n.m.r. spectroscopy, methylation analysis, and fast-atom bombardment-mass spectroscopy (f.a.b.-m.s.) indicated that these compounds were 6-O-α-D-glucopyranosylcyclomaltohexaose (1), 6-O-α-D-glucopyranosylcyclomaltoheptaose (2), and 6,6'''-di-O-α-D-glucopyranosylcyclomaltoheptaose (3).
- Koizumi, Kyoko,Utamura, Toshiko,Sato, Michikatsu,Yagi, Yoshiaki
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- SUPPRESSION OF THE CONVERSION OF 3-t-BUTYL-1-METHYL-1-NITROSOTHIOUREA TO 3-t-BUTYL-1-METHYLUREA BY β-CYCLODEXTRIN UNDER ACIDIC CONDITIONS
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The denitrosation of 3-t-butyl-1-methyl-1-nitrosothiourea (1) was retarded by β-, and γ-cyclodextrins (CDs) at pH 4.70.Decomposition of 1 in the presence of β-CD produced selectively 3-t-butyl-1-methylthiourea (1a), which was remarkably different from the product ratio in the absence of β-CD.These results may be caused by both the protective and the microsolvent effect of β-CD.
- Isobe, Masayoshi
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- INCLUSION, SOLUBILIZATION, AND STABILIZATION OF TWO ELECTRON REDUCED SPECIES OF METHYL VIOLOGEN BY CYCLODEXTRINS
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An electrochemical investigation of methyl viologen-cyclodextrin (CD) system has revealed that β-CD has outstanding ability to include the 2e reduced species of methyl viologen in aqueous solution (formation costant: 1400 dm3 mol-1) in comparison with other CDs and the inclusion solubilizes and stabilizes the electrogenerated species.
- Matsue, Tomokazu,Kato, Tetsuya,Akiba, Uichi,Osa, Tetsuo
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p. 1825 - 1828
(2007/10/02)
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- Structural Effect of Guest Molecules upon the Stability of Inclusion Complexes of 5-(4-Hydroxyphenylazo)naphthalene-1-sulphonic Acid and Some Substituted Analogues with Cyclodextrins
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In order to examine the structural effects of substituted azo compounds upon the stability of inclusion complexes with cyclodextrins, the inclusion equilibria of various types of o-hydroxyphenylazo derivatives of naphthalenesulphonic acid with α- and β-cyclodextrins in aqueous solution have been studied by u.v.-visible spectroscopy.The stability of the inclusion complexes depends primarily on the size and the shape of the alkyl substituent of the azo compounds as guest molecule and the diameter of the cavity of the cyclodextrin as host molecule.It is found that the complementary geometry between the guest and the host molecule is an important factor in determining the stability of the inclusion complexes.The molecular disposition of the guest azo compounds in the cavity of the cyclodextrin is examined by the use of 1H-n.m.r. spectroscopy.The rate constants for the inclusion reaction are determined in some α- and β-cyclodextrin systems by stopped-flow and the temperature-jump spectroscopy.The activation parameters for the inclusion reactions are evaluated from the temperature dependence of the rate constants.Compensation effects are observed between the enthalpy of activation and the entropy of activation for the inclusion reactions.
- Yoshida, Noboru,Fujimoto, Masatoshi
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p. 2424 - 2460
(2007/10/02)
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- KINETIC STUDIES OF AZO DYE-α-CYCLODEXTRIN COMPLEXES. EVIDENCE FOR AN ISOMERISATION STEP
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The kinetics of complex formation of a series of azo dyes with α-cyclodextrin (cyclomaltohexaose, α-CD) were examined by means of the temperature-jump method at pH 7.2, an ionic strength of 0.15M, and a temperature rise to 25 deg C.All dyes were azobenzen
- Oerstan, Aydin,Wojcik, John F.
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