Inclusion complexes of alcohols with α-cyclodextrin

Calorimetric studies of the inclusion complexes of straight and branched alcohols and of diols with alpha-cyclodextrin (-CD) have been carried out in water solvent. The data suggest that straight and branched chain alcohols enter the cavity of -CD alkyl end first. The hydroxyl group hydrogen bonds to the outer oxygen ring of the cyclodextrin. For branched chain alcohols the longer alkyl part of the molecule penetrates the -CD cavity up to the hydroxyl group. Diols form two hydrogen bonds to the outer oxygen ring of the cyclodextrin with some penetration into its interior.     

Energetics of Water/Cyclodextrins Interactions

The heat capacities of solid -CD, 8.1 H₂O and -CD, 6.0 H₂O have been measured between 10 and 300 K by adiabatic calorimetry. Using earlier results obtained in similar experiments with anhydrous cyclodextrins and with -CD, 9.7 H₂O, a comparative analysis has been developed. The energetic behaviours of anhydrous and hydrated cyclodextrins (CDs) have been compared in order to investigate the role of water molecules in the stabilization of the cyclodextrin's rings and on their reactivities. Calculations, based on the additivity of thermodynamic properties, provide the energetic and entropic average contributions of water molecules in each cyclodextrin. From these results, we assumed that the water–water and water–CD interactions are rather different according to the cyclodextrin. In the (-CD, 9.7 H₂O) structure, the water molecules seem to be better organised in a relatively independent network. Concerning hydrated -CD and -CD, stronger water–CD interactions probably prevent an optimal organisation of the water–water bonds network. Differential scanning calorimetry was also used to follow the evolution of the thermal behaviour of -CD, nH₂O versus hydration ratio between 170 and 300 K. Our results indicate that the -CD ring needs at least 1.6 water molecules to be stabilized in the solid state.     

Formation of Supramolecular Polymers Constructed by Cyclodextrins with Cinnamamide

-Cyclodextrin having cinnamamide at 6- or 3-positions (6-CiNH--CD, 3-CiNH--CD) and -cyclodextrin with cinnamamide on 6-position (6-CiNH--CD) have been prepared. Supramolecular structures were formed in the solid state or aqueous solutions and characterized by measurements of NMR and vapor pressure osmometry (VPO). The results indicate that 6-CiNH--CD formed insoluble supramolecular polymers in the solid state, while 6-CiNH--CD and 3-CiNH--CD formed supramolecular complexes in aqueous solutions. 6-CiNH--CD was found to form a dimer in an aqueous solution. 3-CiNH--CD formed intermolecular complexes to give supramolecular polymers. The differences of the position of guest part on cyclodextrins caused to give a variety of supramolecular structures in aqueous solutions.     

Charge-transfer Interaction: A Driving Force for Cyclodextrin Inclusion Complexation

PM3 calculations were performed on the complexation of -cyclodextrin (-CD) with nitrobenzene, benzoic acid, benzoate anion, 4-nitrophenol, and 4-nitrophenolate anion. The results, in agreement with the experimental observations, indicated that the complex -CD-benzoic acid was more stable than -CD-nitrobenzene, and -CD-4-nitrophenolate was more stable than -CD-4-nitrophenol. Frontier orbital analysis suggested that charge-transfer interaction led to such behaviors, and hence constituted a nontrivial driving force in the molecular recognition of -CD.     

Structure and molecular dynamics of solid-state inclusion complexes of cyclodextrin and permethylated cyclodextrin with benzaldehyde studied by high-resolution CP/MAS13C NMR

The structure and molecular dynamics of the benzaldehyde inclusion-complexes with -and-cyclodextrins and permethylated -cyclodextrin in the solid state have been studied by high-resolution cross-polarization/magic angle sample-spinning¹³C NMR spectroscopy. It is shown that the guest benzaldehyde molecule undergoes motion in the host cyclodextrin cavity and the rate of motion depend on the cavity size. In the -cyclodextrin complex, compared to -and permethylated -cyclodextrin complexes, the benzaldehyde motion is severely restricted, but under high-vacuum benzaldehyde is released more easily from the cavity.     

Supramolecular Chemistry of Cyclodextrin-Peptide Hybrids: Azobenzene-Tagged Peptides

AC17, which is composed of 17 amino acids and has an azobenzene moiety but has no cyclodextrin (CD) unit in the side chain, exhibits 54% helix content. However, AC17, which has both trans-azobenzene and -CD, shows 82% helix content. This result suggests that the helix structure is stabilized by host (CD)-guest (azobenzene) bridge in the side chain of the peptide. The helix content changed by trans-cis photoisomerization as shown by 64% helix content for AC17 in its cis form. This result suggests that cis-azobenzene unit is excluded from the -CD cavity, thus resulting in the smaller helix content. The helix contents for AC17, which has both azobenzene and -CD, are 94% in the cis form and 87% in the trans form, suggesting that the cis form is included in the -CD cavity. Azobenzene-tagged CD-peptide hybrids with histidine unit were also prepared and photoregulation of catalytic activity in ester hydrolysis was examined.     

Cyclodextrin-accelerated oxidation of iodide by oxygen in aqueous solutions containing HClO4

The oxidation of iodide to I ₃ ^– by oxygen dissolved in water containing HClO₄ has been found to be accelerated by -cyclodextrin (-CD). Among -, -, and -CDs, -CD is the most effective mediator for the oxidation reaction of iodide by oxygen. The oxidation rate of iodide is first order in the concentrations of -CD and HClO₄, whereas it is second order in the KI concentration.Part of this work was carried out at Department of Physics, Miyazaki Medical College, Miyazaki 889-16, Japan.     

Complex formation between α-cyclodextrin and amines in water and DMF solvents

Complexation between -cyclodextrin (-CD) and aliphatic amines in water and DMF solvents was studied by calorimetry. Amines form complexes with -CD in both solvents but the nature of the complexes is quite different. In DMF the amines donate a hydrogen from the amine N–H group to the cyclodextrin forming a normal hydrogen bonded complex. In DMF solutions with large amine concentrations, complexes other than 11 are observed. In contrast, in aqueous environment the amines form inclusion complexes in which the amine alkyl group penetrates the -CD cavity and is stabilized by van der Waals interactions. The equilibrium constants for the complexes formed in water solvent increase with increasing alkyl chain length due to an entropy effect.     

Asymmetric halogenation and hydrohalogenation of styrene in crystalline cyclodextrin complexes

Asymmetric halogenation and hydrohalogenation of styrene in microcrystalline cyclodextrin complexes were studied in the gas-solid state, and compared with the homogenous reactions in aqueous or dimethyl sulfoxide solutions. The gas-solid brominations in the - and -cyclodextrin complexes produced predominantly (–)-1,2-dibromo-l-phenylethane. The chiral induction for the reaction of the -cyclodextrin complex rose to 9 times that of the -cyclodextrin complex. Brominations in the homogenous solutions containing the - or -cyclodextrin complexes gave no dibromide but racemic bromohydrin. In the gas-solid chlorination, the -cyclodextrin complex gave (–)-dichloride,S-(+)-2-chloro-l-phenylethanol (14% ee) and (+)-1,2,2-trichloro-l-phenylethane, and the -cyclodextrin complex produced (+)-dichloride,S-(+)-chlorohydrin (8% ee) and (+)-trichloride. The chiral induction of the gas-solid halogenation using the solid cyclodextrin complexes is attributed to the ability to hold rigidly a chiral conformation of the crystalline state. However, the gas-solid hydrohalogenation all gave racemic products.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Thermal Behaviour of Anhydrous α-, β- and γ-Cyclodextrin at Low Temperature

Heat capacities of anhydrous -and -cyclodextrin were measured by adiabaticcalorimetry between 10 K and 300 K. The thermalbehaviour of the two compounds exhibits significantdifferences. -Cyclodextrin shows an anomalousexcess heat capacity in the entire region between 70 Kand 210 K. In the case of -cyclodextrin, anendothermic effect is observed at 240K. This effect isanalysed through the study of the correspondingentropy change and discussed in terms ofintramolecular organization.Using the known heat capacity values of anhydrous-CD, a comparative analysis has been developed.For each cyclodextrin, the average behaviour of abound -D-glucopyranose has been calculated andcompared. From a thermodynamic point of view, thedegree of organization of the dehydrated macrocycliccompounds could be expressed as-CD -CD -CD.     

Supramolecular Polymers Formed by Modified Cyclodextrins

6-Hydrocinnamoyl -cyclodextrin(6-HyCiO--CD), 6-hydrocinnamoyl -cyclodextrin(6-HyCiO--CD), 6-cinnamoyl -cyclodextrin(6-CiO--CD), and 6-cinnamoyl -cyclodextrin (6-HyCiO--CD) have been prepared.6-HyCiO--CD formed an intramolecular complex in an aqueous solution. 6-HyCiO--CD formed weak intermolecular complexes.6-CiO--CD formed intermolecular complexes to give supramolecular oligomers. 6-CiO--CD formed insoluble supramolecular complexes in the solid state. The structures of these complexes are discussed.     

Concentration of indole in coal tar using α-cyclodextrin as the host for inclusion complexation

Inclusion complexation by -cyclodextrin (-CD) was utilized to develop a novel method of extracting indole in coal tar. An aqueous solution of -CD and a sample oil containing indole was stirred to form a solid -CD-indole complex. Both model and real sample oils were tested. Composition changes of the sample oils accompanied by the inclusion process were measured with capillary gas chromatography. -CD was found to have the remarkable characteristic of concentrating indole selectively even in a complicated mixture.     

Chemistry of the lipids

Conclusions 1. A. new route for the synthesis of optically active ,-diglycerides has been developed.2. D- and L-, -Distearins and D-, -dilinolenin have been synthesized from the readily accessible L- and D--O-tritylglycerols.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 4, pp. 210–214, 1969     

Preparation and properties of cyclodextrin inclusion compounds of organometallic complexes. Ferrocene inclusion compounds

Inclusion compounds of ferrocene(FcH) and its derivatives with cyclodextrins(CDs; -CD, -CD, and -CD) were prepared. CD-ferrocene inclusion compounds were obtained in a crystalline state in high yield. -CD and -CD formed 11 stoichiometric inclusion compounds with ferrocene and its derivatives. -CD formed 21 (CD:guest) complexes with ferrocene and the monosubstituted derivatives, but did not form complexes with 1,1-disubstituted derivatives, -CD-FcH and -CD-FcH complexes are thermally stable and do not liberate ferrocene on heating at 100°C in vacuo. The cyclodextrin inclusion compounds were characterized by¹H-NMR, IR, UV, and CD spectra. A large positive induced Cotton effect was observed in the case of -CD-FcH complex, while the -CD-FcH complex showed a negative spectrum. The binding mode is discussed. -Cyclodextrin was found to form inclusion complexes in ethylene glycol, diethylene glycol, triethylene glycol, methyl cellosolve, ethyl cellosolve, methyl alcohol, and glycerine solutions. -CD also formed complexes in ethylene glycol solution. The binding of ferrocene by -CD is stronger in ethylene glycol than in dimethyl sulfoxide and dimethyl formamide.     

Inclusion Complexes of Atrazine with α-, β- and γ-Cyclodextrins. Evidence by Polarographic Kinetic Currents

The reduction of atrazine in acidic aqueous media on mercury electrodes proceeds only after the protonation reaction. In fact, the efficiency of the reduction process is very low at pHs greater than 4. However, the addition of cyclodextrins (CDs) to neutral aqueous solutions of atrazine yields a kinetically controlled polarographic reduction wave, whose limiting current depends on the size of the CD cavity, and increases with the concentration of the CD itself. In particular, the size of the increase follows the order -CD < -CD < -CD for the same CD concentration. The half-wave potential shifts toward more negative values when the concentration of CDs increases. These findings lead to the conclusion that atrazine and CDs form an inclusion complex, whose stability constant we have estimated, and also that atrazine undergoes protonation facilitated by complexation with CDs. The stability constants of 1:1 complexes evaluated from polarographic data in 0.1M-KCl and at neutral pH for -CD, -CD and -CD are 4900, 1970 and 19000, respectively. The formation of the inclusion complex was indirectly confirmed by UV-Vis measurements in the presence of methylred and phenolphthalein, which both compete with atrazine in the formation of the corresponding inclusion compounds with CDs.     

Geometry of α-cyclodextrin inclusion complex with m-nitrophenol deduced from quantum chemical analysis of carbon-13 chemical shifts

The host-guest orientation and the position of the guest m-nitrophenol (MNP) in the -cyclodextrin (-CD)-MNP inclusion-complexation induced carbon-13 NMR chemical shifts of MNP with those predicted by quantum chemical calculation. In the calculation, the non-polar environmental effect produced by the -CD cavity on the carbon-13 shifts of included guest molecule has been formulated by the so-called NMR solvent effect theory. Here, carbon-13 shift displacements are assumed to be induced by transference of the guest from polar aqueous phase with higher dielectric constant to the non-polar -CD cavity with lower dielectric constant. Among a variety of host-guest orientation investigated, only the geometry in which the nitrophenyl group is located in the -CD cavity and the hydroxyl groups is exposed to the aqueous phase can reproduce qualitatively the observed carbon-13 shift displacements of MNP. This geometry is consistent with that in the solid state determined by the X-ray method.     

1H-NMR Investigation of the Binding of 2-Methylnaphthalene to α-Cyclodextrin in D2O Solutions

As -cyclodextrin (-CD) was added to D₂Osolutions of 2-methylnaphthalene, its proton signals shifted to lower fieldsat low concentrations of -CD. At 2.0 × 10^-2 moldm^-3 of -CD, however, a reverse, higher-field shift wasobserved for the H-8 signal, indicating the formation of 1 : 1 and 2 : 1-CD–2-methylnaphthalene inclusion complexes. Intrinsic chemicalshift differences of all the protons in 2-methylnaphthalene have beenevaluated for both the 1 : 1 and the 2 : 1-CD–2-methylnaphthalene inclusion complexes. These intrinsicchemical shift differences suggest that the first -CD molecule has noselectivity in accommodating one end of uncomplexed 2-methylnaphthalene;-CD binds to a methyl group, as well as a naphthalene ring-end havingno methyl group, to form the 1 : 1 inclusion complex, resulting in theformation of two kinds of 1 : 1 complexes.     

A structural investigation of a D-glucan fromYersinia pseudotuberculosis of serotype VI

It has been established that an -D-glucan isolated fromYersinia pseudotuberculosis, serotype VI, is branched and contains -14- and -16-bound D-glucopy-ranose residues in the main chain and the side chains, respectively.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostock. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 151–154, March–April, 1981.     

Study of Inclusion Complexes of Cyclodextrins with Orange II

Inclusion reactions of - and -CD with Orange IIwere measured by means of a stopped-flow method and UV-spectra. The forward rate constants (k₊), backward rateconstants (k_-) and the equilibrium constants (K) for the inclusion reactions were determined. Theinclusion processes of CD with Orange II follow a one-step reaction mechanism. The value of the forward rate constantat neutral and alkaline conditions for Orange II binding to -CD cavity was large. This suggests that thenaphthalene side is partially included in the final complex form. In the case of -CD, only marginal differenceis shown.It is probable that inclusion covers the whole naphthalene group and part of the azo group as well,resulting ina small effect from the pH variation. The results show that the equilibrium constant at pH 7 for the binding ofOrange II to -CD is the largest because the included part of Orange II matches the cavity of -CD well.     

Kinetics of isotope exchange of dioxygen with a powdered high-temperature superconducting material Ba2YCu3O7?x

It has been found that the rate of isotope exchange in Ba₂YCu₃O_7–x–O₂ system is high. Its kinetics is exponential, first order with respect to dioxygen and the exchange is of the mixed first/third type.

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Ba₂YCu₃O_7–x–O₂ . -, -, - .