Inclusion Behavior of α-Cyclodextrin with 2-Methylnaphthalene in Aqueous Solutions

By means of absorption and fluorescence spectroscopy, 2-methylnaphthalene (2MN) was found to be incorporated into the cavity of -cyclodextrin (-CD) to form a 1 : 1 inclusion complex. The 1 : 1 inclusion complex further associated with another -CD molecule, resulting in the formation of a 2 : 1 -CD-2MN inclusion complex. The equilibrium constants for the formation of the 1 : 1 and 2 : 1 inclusion complexes were estimated to be 44.6 and 376 mol-1 dm3, respectively, on the basis of a simulation of the observed 2MN fluorescence intensities. The induced circular dichroism spectra suggested that 2MN, buried within the -CD inclusion complexes, resided in a different orientation relative to the CD symmetry axis, as compared to 2MN within a -CD inclusion complex.     

1H-NMR Study on Inclusion Modes of 2-Chloronaphthalene and α-Cyclodextrin in D2

Abstract

With a 1:1 and a 2:1 host-guest stoichiometry, α-cyclodextrin (α-CD) forms inclusion complexes with 2-chloronaphthalene. From simulations concerning observed chemical-shift differences (Δδ_obs) of proton signals of 2-chloronaphthalene, intrinsic Δδ values are estimated for all the guest protons in the 1:1 and 2:1 inclusion complexes. The intrinsic Δδ values indicate that α-CD first binds to a part of a naphthalene ring bearing a C1 atom to form the 1:1 inclusion complex. In the 1:1 and 2:1 inclusion complexes, the symmetry axes of α-CD are tilted approximately 30° relative to a naphthalene longitudinal axis. In the 2:1 inclusion complex, the association through hydrogen bonding most likely occurs between two α-CD molecules whose symmetry axes are laterally shifted.     

Thermodynamics of Binding of α:-Cyclodextrin to Straight-Chain Alkyl Derivatives in Aqueous Solution

Apparent standard Gibbs energy, enthalpy, entropy, and heatcapacity data of the interactions of -cyclodextrin (CD) to some n-carboxylatesH(CH₂)_nCOO^- (n = 4–6), are determined by isothermal titration microcalorimetryat different temperatures in phosphate buffer, pH 9.0, assuming a 1 : 1 model indilute solution. Modelling of contributions of the thermodynamic properties of the solutionindicates that CD undergoes conformational change upon binding to homologousseries of n-carboxylates, n-alcohols, ,-alkane dicarboxylates and ,-alkane diols.     

Inclusion of Polyphenol Oxidase Substrates in β-Cyclodextrin: A 1 H-NMR Study

A ¹H-NMR study of the interactionsbetween -cyclodextrin (-CD) and included phenolic molecules (chloragenic acid and caffeic acid ) in aqueous medium is reported. The results confirm that inclusion occurs. Data analysis by the continuous variation method shows that all the complexes have 1 : 1 stoichiometries. Values for the apparent association constants of the inclusion compounds are estimated and compared with previously reported values.     

Molecular Mechanics Study of the Inclusion of Trimethylbenzene Isomers in α-Cyclodextrin

Molecular mechanics calculations were employed to study the inclusion of triethylbenzene isomers in -cyclodextrin and their solvation energy in aqueous solution. Trimethylbenzene penetrates partially into the cavity of -cyclodextrin to form 1 : 1 or 2: 1 host–'guest complexes. The interaction energy between host and guest is dominated by van der Waals energy. The inclusion complexes have higher solvationenergies than free -cyclodextrin.     

A Study on the Driving Force for Binding of Benzene Derivatives by α-and β-Cyclodextrin

WehavedemonstTatedthattheassociationconstantsfortheinclusioncomplexationofa-and6-cyclodextrin(a-and9-CD)withsubstitutedbenzene(PhX)arecorrelatedwithpropertiessuchasmolarrefraction(R.),hydrophobicity(n.)andeIectroniceffect(a.)ofsubstitUentsintheguestcompounds.Uponapplicationofanariificialneuralnetwork(ANN),theassociationconstants(Ka)fortheinclusionofa-CDand6-CDwithsubstitutedbenzenewerepredictedfromR.,rrxandG.withsatisfactoryresultSl'2.Furthermore,theeffectsofsubstituentsinbenzenederivat…     

Effect of β-Cyclodextrin Upon the Sol-gel Transition of Methylcellulose Solutions in the Presence of Sodium Dodecyl Sulfate

The sol-gel transition temperature of methylcellulose (MC) solution in the presence of sodium dodecyl sulfate (SDS) as well as the mixtures of SDS and β-cyclodextrin (β-CD) was mea-sured, and the effect of the two competing interactions, the hydrophobic interaction between SDS and MC and the inclusion interaction between SDS and β-CD, upon the sol-gel transi-tion of MC solution was studied. It has been found that the inclusion interaction between SDS and β-CD is much greater than the hydrophobic interaction between SDS and MC. As a result, in the coexistence of SDS and β-CD, the sol-gel transition temperature of MCsolution keeps the same value, independent of the concentration of SDS in solution on con-dition that the concentration of SDS is less than β-CD. Our experimental results not only suggest that the effect of SDS upon the sol-gel transition of MC solution can be screened by β-CD completely but also indicate the inclusion ratio of SDS to β-CD can be determined quantitatively by using rheological measurement. The inclusion ratio of SDS to β-CD is 1:1, which is in good agreement with the inclusion ratio of SDS to β-CD in the presence of poly(vincyl pyrrolidone) determined by the viscosity measurement but is critically differentfrom the inclusion ratio of SDS to β-CD in the presence of the oppositely charged polyelec-trolyte by using the rheological measurement, mainly due to the reason that the mechanism of the interaction between SDS and MC is critically different from the mechanism of the interaction between SDS and the oppositely charged polyelectrolyte.     

Study of Products of the Aqueous Chlorination of 2-Methylnaphthalene and α-Naphthol by Chromatography–Mass Spectrometry

Qualitative and quantitative analysis of products of the aqueous chlorination of 2-methylnaphthalene and -naphthol was performed by chromatography–mass spectrometry. Detailed schemes of their transformation under the conditions modeling the process of disinfection of natural water at water-treatment plants were formulated.     

General Solutions to Some Types of Solitons in the Atmosphere

In terms of the Bargmann potential technique the problem of solutions to atmospheric solitary waves is investigated with the derivation of the solutions and their dispersion relations of such solitary waves as of inertial, internal gravity and Rossby modes, and some further appreciation and significant outcome have been achieved.     

Investigation on the Binding of Terazosin Hydrochloride and Naftopidil to an Immobilized α 1-Adrenoceptor by Zonal Elution

The interaction between drugs and receptors is particularly important in revealing the drug acting mechanism and developing new leads. In this work, α ₁-Adrenoceptor (α ₁-AR) from HEK293 cell line is purified and immobilized on the surface of macro-pore silica gel to prepare an high-performance affinity chromatography stationary phase for the pursuit of drug–receptor interactions by competition zonal elution. Naftopidil is found to have only one type of binding site to α ₁-AR with an association constant of 1.45 × 10⁶ M⁻¹ and a concentration of binding sites of 1.56 × 10⁻⁶ M, while terazosin hydrochloride proves to present two kinds of binding site on the receptor at which the association constants are determined to be 1.61 × 10⁵ M⁻¹ and 2.06 × 10³ M⁻¹, and the corresponding concentrations of the binding sites are 1.56 × 10⁻⁶ M and 1.11 × 10⁻³ M, respectively. It is concluded that the stationary phase containing attached α ₁-AR can be used to realize the binding of a drug to the receptor.

     

1H-NMR Studies of the Inclusion Complexes between α-Cyclodextrin and Adamantane Derivatives Using Both Exchangeable Hydroxy Protons and Non-Exchangeable Aliphatic Protons

The inclusion complexes between -cyclodextrin (-CD) and adamantane, 1-adamantanol, 1-(hydroxymethyl)-adamantane, 2-adamantanol, and 1,3-adamantanediol in aqueous solution have been studied by ¹H-NMR spectroscopy using both non-exchangeable and exchangeable protons. The complexation-induced ¹H-NMR shifts (CIS) and NOEs of non-exchangeable protons, as well as the CIS, NOEs, temperature coefficients, and linewidth of signals from exchangeable hydroxy protons have been determined. The stoichiometry of the adamantane/-CD complex could not be determined due to the low solubility of adamantane. However, for 0.11 equivalent of adamantane added, two sets of separate ¹H signals for the free and bound -CD were observed. The signal from O(3)H in the complexed form appeared narrow and upfield shifted with a low-temperature coefficient indicating reduced hydration inside the hydrophobic cavity of -CD. Both 1-adamantanol, and 1-(hydroxymethyl)-adamantane formed 1:1 inclusion complexes with -CD and only one set of NMR signals was observed. The CIS and NOEs suggested that both complexes had similar structures. The O(2)H signal of -CD was broadened at low temperature and became narrower as the temperature raised. The broadening increased with higher concentration of guest suggesting interaction between O(2)H of -CD and the guest molecules. The stoichiometry of the -CD/2-adamantanol complex could not be determined with certainty, but the NMR data suggested equilibrium between 2:1 and 1:1 complex. As with adamantane, a sharp and upfield shifted O(3)H signal with a very low-temperature coefficient was observed. No inclusion complex was formed between 1,3-adamantanediol and -CD. This study showed how the hydroxy protons of -CD could be used to obtain complementary information on the geometry and stability of inclusion complexes of -CD.     

Investigation of the phosphinyl analog of α-ketoglutaric acid

It was shown by³¹P and¹³C NMR spectroscopy that methyl(3-carboxy-3-oxopropyl)phosphinic acid (4-methylhydroxyphosphinyl-2-oxobutyric acid) (1) and the amide (2) of the latter exist in keto forms in non-aqueous solutions. In aqueous solutions an equilibrium between the keto,gem-diol, and enol forms has been observed. The proportions of the diol and enol forms increase as the acidity of the media increases. Silylation of acid 1 with hexamethyldisilazane gives the tris(trimethylsilyl) derivative of enol form (3) (Z- andE-isomers).Translated fromIzyestiya Akadetnii Nauk. Seriya Khimicheskaya, No. 1, pp. 125–128, January, 1994.     

Investigation on the Binding of Terazosin Hydrochloride and Naftopidil to an Immobilized α 1-Adrenoceptor by Zonal Elution

The interaction between drugs and receptors is particularly important in revealing the drug acting mechanism and developing new leads. In this work, α ₁-Adrenoceptor (α ₁-AR) from HEK293 cell line is purified and immobilized on the surface of macro-pore silica gel to prepare an high-performance affinity chromatography stationary phase for the pursuit of drug–receptor interactions by competition zonal elution. Naftopidil is found to have only one type of binding site to α ₁-AR with an association constant of 1.45 × 10⁶ M^?1 and a concentration of binding sites of 1.56 × 10^?6 M, while terazosin hydrochloride proves to present two kinds of binding site on the receptor at which the association constants are determined to be 1.61 × 10⁵ M^?1 and 2.06 × 10³ M^?1, and the corresponding concentrations of the binding sites are 1.56 × 10^?6 M and 1.11 × 10^?3 M, respectively. It is concluded that the stationary phase containing attached α ₁-AR can be used to realize the binding of a drug to the receptor.     

A Microcalorimetric Study of Host–Guest Complexes of α-Cyclodextrin with Alkyl Trimethyl Ammonium Bromides in Aqueous Solutions

Interactions between α-CD and three alkyl trimethyl ammonium bromides, a homologues series of surfactants, in aqueous solutions have been investigated with titration microcalorimetry at 298.15 K. The results are discussed in the light of the amphiphilic interaction and the iceberg structure of water molecules existing around the hydrophobic tail of the surfactant. The stoichiometry of the host–guest complex changes from 1:1 to 2:1, as the number of carbon atoms (n) in the hydrophobic chain, C_nH_2n+1, increases from 8 to 14. All the complexes are quite stable, with the apparent experiential stability constants being β₁ = 2.65 × 10³ dm³-mol⁻¹, β₂ = 4.85 × 10⁶ dm⁶-mol⁻², β₂ = 6.50 × 10⁶ dm⁶-mol⁻², respectively for n = 8, 12, 14. All the complexation processes are shown to be enthalpy driven, and the standard enthalpy effect (−ΔH⁰) increases while standard entropy change (ΔS⁰) decreases with elongation of the hydrophobic chain.     

Investigation of rotational isomerism along the C-O bond in α-aryloxycarbonyl compounds

Electrical and electrooptical characteristics of -phenoxycyclohexanone, -phenoxyacetone,p-Me-,p-Cl-,p-Br-,p-NO ₂ -phenoxycyclohexanones, andp-NO ₂ -phenoxyacetone in the solution in CCl ₄ were determined; these were utilized for the conformational analysis of the general structural fragment Ar-O-C-C=O. The presence of conformers with theac- andsp-structure at the C _sp 3-C _sp 2 bond was established in the equilibrium. The content of thesp-form increases with the increase in the polar character of the substituent at thep-position of the benzene ring. Thegauche isomer (sp-G orsp-G) is realized along the C-O bond in it. In theac-conformers, both thegauche (ac-G) and the trans (ac-T) structures can be realized along the C-O bond.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences, Kazan' 420083. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 612–620, March, 1992.     

The Conformation of Some Halodeoxy Analogues of Methyl β-Lactoside in D2O and DMSO-d6 Solutions

Abstract

The solution conformation of several halodeoxy analogues of methyl β-lactoside 1 has been analysed using molecular mechanics and dynamics calculations and nuclear magnetic resonance data (variable temperature and NOE experiments). The overall shape of all the compounds studied is fairly similar and may be described by conformers included in a low energy region with Φ = ?100±40° and Ψ = ?135±35°, that is ca. 5% of the total potential energy surface calculated for the β(1->4) glycosidic linkages of the disaccharides.     

Derivatives Of α-Cyclodextrin and the Synthesis of 6-O-α-D-Glucopyranosyl-α-Cyclodextrin

Abstract

Regioselective silylation of α-cyclodextrin with tert-butyl-dimethylsilyl chloride in N, N-dimethylformamide in the presence of imidazole gave, in 75% yield, the hexakis(6-O-tert-butyldimethylsilyl) derivative 2, which was transformed into the hexakis(2,3-di-O-methyl, 6-O-methyl, 2,3-di-O-propyl, and 2,3-di-O-acetyl) derivatives. On methanesulfonylation and p-toluenesulfonylation, the hexakis(2,3-di-O-acetyl) derivative 16 afforded the hexakis(2,3-di-O-acetyl-6-O-methylsulfonyl 17 and 2,3-di-O-acetyl-6-O-p -tolylsulfonyl 18) derivatives, respectively. Nucleophilic displacement of 17 and 18 with iodide, bromide, chloride, and azide ions afforded the hexakis(6-deoxy-6-iodo 19, 6-bromo-6-deoxy, 6-chloro-6-deoxy, and 6-azido-6-deoxy) derivatives, respectively, of α-cyclodextrin dodeca-acetate. The hexakis (2, 3-di-O-acetyl-6-deoxy) derivative was prepared from 19. Selective glucosylation of 16 with 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl bromide under catalysis by halide ion, followed by removal of protecting groups, furnished 6-O-α-D-glucopyranosyl-α-cyclodextrin.     

New method for studying the reactivities of α-diazo imines. Investigation of the cyclization of N-substituted 2-diazoacetamidines to 1,2,3-triazoles

N-Substituted diazoacetamidines were generated in the reaction of N-substituted acetamidines with benzenesulfonyl azide. It is shown that their cyclization to isomeric 1,2,3-triazoles characterizes the reactivities of -diazo imines. The synthesis of 5-amino-1,2,3-triazole derivatives was accomplished, and their ¹H, ¹³C, and ¹⁵N NMR spectra were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 775–782, June, 1991.     

Investigation of Inclusion Complexes Between α-Cyclodextrin and Ferrocene by ESI-MSn and Cyclic Voltammetry

The inclusion complexes of α-cyclodextrin(α-CD) and FcCO2(CH2)18 (FcSH) and their self-assembled monolayers(SAMs) on gold surface were investigated by electrospray tandem ionization mass spectrometry(ESI-MSn) and cyclic voltammetry, respectively. The interfacial electrochemical response of the SAMs is related to the way in which the inclusion complexes formed.