Inclusion of the regioisomeric nitrobenzene derivatives and ferrocene guests by β-cyclodextrin polymer and their transport through the polymer matrix

Host-guest equilibria have been investigated involving inclusion sites of the microparticulate amorphous β-cyclodextrin polymer, β-CDP-25, and a range of redox guests comprising regioisomeric nitrobenzene derivatives and ferrocene. The equilibria were studied by the batch method. Inclusion-governed, Langmuir-type sorption equilibria occurred in the β-CDP-25/guest systems studied in 1:1 (v/v) aqueous methanolic solutions. A 1:1 (host inclusion site)/guest stoichiometry was found and sorption equilibrium constants were determined. The values of the constants changed by a factor of 20 between the most weakly and strongly included guests. Regioselective discrimination of β-CDP-25 was most pronounced with respect to nitrophenols. Transport phenomena of guest molecules in the β-CDP-25 matrix have also been studied. The apparent diffusion coefficients of guest molecules were determined in the β-CDP-25 matrix by chronamperometry at the (β-CDP-25)-PTFE-carbon composite electrodes. These diffusion coefficients were almost four orders of magnitude lower than the corresponding coefficients of guest molecules in solution in the absence of β-CD. The diffusion mechanism was postulated for the guest molecules in the β-CDP-25 matrix, which invoked hopping of the molecules between inclusion sites.     

Electrochemically initiated fragmentation reaction of 9,9′-dinitro-9,9′,10,10′-tetrahydro-10,10′-bianthryl

A mechanism for the electroreduction of 9,9-dinitro-9,9,10,10tetrahydro-10,10-bianthryl in DMF, which results in the formation of anthracene and 9-nitroanthracene has been proposed on the basis of data from polarography, cyclic voltammetry, and electrolysis at a controlled potential.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1321–1325, June, 1991.     

Inclusion of neutral guests by water-soluble macrocyclic hosts – a comparative thermodynamic investigation with cyclodextrins,calixarenes and cucurbiturils

Abstract

The driving forces of association between three different families of macrocycles as hosts, namely cyclodextrins (α-, β-, and γ-), p-sulfonatocalix[n]arenes (n = 4–6) as well as cucurbit[n]urils (n = 6–8), and three different bicyclic azoalkane homologues as guests, namely 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH), 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) as well as 2,3-diazabicyclo[2.2.3]non-2-ene (DBN), were examined by means of calorimetric titrations, NMR spectroscopy and molecular dynamics simulation, all in aqueous solution. The small, spherical and uncharged guests preferably bind inside the cavities of the medium sized hosts. The inclusion complexation by β-cyclodextrin and p-sulfonatocalix[4]arene shows medium binding affinities (millimolar), while cucurbit[7]uril macrocycle shows very strong binding (micromolar). For all types of macrocycles, the complex formation is enthalpically driven (ΔH° < 0), accompanied by slightly unfavourable entropy changes (ΔS° < 0). The results are discussed in terms of the flexibility of the hosts, the hydrophobic character of their cavities and the release of high-energy water upon binding, and generalised by including two additional guests, the ketones cyclopentanone and (+)-camphor.     

Experimental and theoretical investigations of absolute stereochemistry and chiroptical properties of enantiopure 2,2′-substituted 9,9′-bianthryls

The absolute stereochemistry of axially chiral 2,2′-X₂-9,9′-bianthryls (X=COOH, COOMe, and Cl) was determined by X-ray analysis of the (+)-quinidine salt of the diacid to be (M)-(−) or (P)-(+). The M isomers of these compounds showed specific rotations of −115, −123, and −32, respectively, in acetone. The circular dichroism (CD) as well as UV spectra of the two M isomers (X=COOMe and Cl) were investigated with the aid of theoretical calculations by the time-dependent DFT (TDDFT) method. The calculations reasonably reproduced the observed CD bands, and suggested a correlation between the signs of p or β′ bands and the absolute stereochemistry.     

Chemical modification of chlorinated rubbers—III. Quantitative study of the grafting of chlorinated rubber by aminoesters and versamids

A quantitative study of the grafting of chlorinated rubber by ethyl 11-aminoundecanoate is carried out. A self-condensation of the aminoester takes place during the grafting; its extent is determined. The grafting of CR by versamid 100 (acetylated or not) is studied quantitatively by several analytical methods (i.r., ¹H- and ¹³C-NMR) and they are compared with respect to accuracy. Non-crosslinked versamid-grafted-chlorinated rubber is obtained.     

Inclusion of Cl− or Br− anions within host framework formed by second-sphere interactions

In this study, we have deliberately utilized the second-sphere coordination approach into the construction of supramolecular inclusion solids Cl ? [H₂ L1]·[InCl₄] (Crystal I) and Br ? [H₂ L1]·[TeBr₆] (Crystal II). The chloride or bromine anions can be encapsulated inside the host assemblies formed by the diamine molecule (4,6-dimethyl-1,3-phenylene) bis(N,N-dibenzylmethane) (L1) and the metal complexes ([InCl₄]^? and [TeBr₆]^2?) via second-sphere interactions. The inclusion complexes have been structurally characterized by X-ray crystallography, indicating that weak C–H···Cl and C–H···Br hydrogen bonding synthons play a significant role in the construction of host framework. 2-D networks are formed in both complexes by the interconnection of 1-D networks through the multiple weak hydrogen bonding interactions with [InCl₄]^? or [TeBr₆]^2?. The guest Cl^? or Br^? anions are encapsulated inside the host cages through N–H···Cl hydrogen bonds. The inclusion selectively was studied for the two host assemblies.     

Complexes of TETROL with selected heterocyclics: unconventional host–guest hydrogen bonding and the correlation with host selectivity

Here we investigate and compare the more salient characteristics of host–guest complexes of (+)-(2R,3R)-1,1-4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) with four heterocyclic guests, morpholine, piperidine, pyridine and dioxane. These guests each formed inclusion compounds with TETROL, and host:guest ratios were either 1:2 or 1:1. Single crystal diffraction experiments revealed unprecedented host behaviour in the presence of both piperidine and dioxane with respect to the mode of host–guest hydrogen bonding employed. Furthermore, by utilizing ¹H-NMR spectroscopy or gas chromatography (as applicable) as methods for analysing complexes obtained from competition experiments, we were able to identify the host selectivity order, and were gratified to discover that this order correlated precisely with host–guest hydrogen bond distance.     

Effect of epoxidation of natural rubber on the pervaporation separation of acetone–chlorinated hydrocarbon mixtures

The pervaporation separation and the swelling behavior of chlorinated hydrocarbon/acetone mixtures were investigated using natural rubber (NR) and epoxidized natural rubber (ENR) membrane with 25 and 50 mol% epoxidation, respectively. The swelling degree increases with increase in the epoxidation level. The flux and separation factor of the membranes were determined both as a function of mole percent epoxidation and of the feed mixture composition. The membranes were found to be permselective to chlorinated hydrocarbons from acetone–chlorinated hydrocarbon mixtures. The flux decreases with increase in epoxidation level, whereas the separation factor increases. The permeation decreases and separation factor increases with increase in the acetone feed concentration. The availability of raw materials, low cost of implementation and easy processability of the system makes this method of separation highly applicable and recommendable.     

Simultaneous Measurement of Adenosine 5′-Triphosphate and its Degradation Products by Reverse-Phase Ion-Pair Chromatography

Abstract

A method is presented for the simultaneous measurement of adenosine 5′-triphosphate and its uv-absorbing degradation products by reversed-phase liquid chromatography using tetra-butylammonium phosphate as an ion-pair agent. The method is suitable for the measurement of these compounds in isolated smooth muscle.     

Enantioselective inclusion of amide guests into a chiral N,N′-ditrityl amino amide host to compensate the loss of hydrogen bonds broken by installation of trityl groups

A new crystalline N,N′-ditrityl amino amide host included several amide guests in the host cavity to form inclusion crystals. Although the installation of trityl groups into (S)-2-aminopropanamide broke its inherent hydrogen bonds of amide groups, inclusion of guest amides compensated the loss of hydrogen bonds. X-ray crystallography showed that these inclusion cavities and host–guest interactions such as hydrogen bonds, van der Waals interaction, and CH?O interactions play important roles for highly enantioselective inclusion. The enantiomeric inclusion was 67% ee (S-form) for N-phenyl 2-methylbutanamide, 82% ee (S-form) for N-phenyl 2-chlorobutanamide, and 83% ee (S-form) for N-phenyl 2-bromobutanamide.     

Study of the vibrational photochemical reation of UF_6+HCl and its isotopic selectivity

The photochemical vibrational reaction of UF_6+HCl was investigated by exciting theternary overtone of 3ν_3 of UF_6 in an intracavity CO laser system.It was found that the rateof the laser-driven reaction was much greater than that of the thermal reaction and thisphotochemical process had an isotopic selectivity.The uranium isotope enrichment factorsmeasured in experiments wore around 1,007 in a single step.     

Two methods for the resolution of 10,10′-dihydroxy-9,9′-biphenanthryl

Two methods for the resolution of 10,10′-dihydroxy-9,9′-biphenanthryl were developed. The first involved salt formation with (−)-strychnine via its cyclic diester with phosphoric acid. The second method involved the formation of diastereomers (R)- and (S)-9,9′-biphenanthryl-10,10′-diyl N-((−)-α-methylbenzyl)phosphoroamidates.     

Facile Synthesis of Ophipogonin C′ and its Three Analogues

Among the huge number of glycoconjuates, the steroidal glycosides are often found as the major components in traditional Chinese medicine. Steroidal glycosides constitute a structurally and biologically diverse class of molecules which have been isolated from a wide variety of both plant and animal species 1. Because of the variety of promising pharmaceutical properties2, the large family of steroidal glycosides has received considerable attention of chemist. Figure 1 OOOOR4R3OR2OOR1O …     

Inclusion complexation of 4,4′-dihydroxybenzophenone and 4-hydroxybenzophenone with α- and β-cyclodextrins

The inclusion complexation behaviours of 4,4′-dihydroxybenzophenone (DHBP) and 4-hydroxybenzophenone (HBP) with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) were investigated using UV–visible fluorescence, time-resolved fluorescence, molecular modelling, scanning electron microscopy (SEM), FTIR, differential scanning calorimeter, X-ray diffraction, ¹H NMR and molecular modelling techniques. In both molecules, biexponential decay was observed in water, whereas triexponential decay was observed in the CD medium. The DSC thermogram of the DHBP/α-CD and DHBP/β-CD inclusion complex nanomaterials shows the endothermic peak at 60.8, 101.9, 119.6 and 112.8°C. The upfield chemical shift observed for HBP protons reveal that the phenyl ring (without hydroxyl substitution) entered the CD cavity and the hydroxyl group of HBP is exposed outside the CD cavity. The SEM image of DHBP appears as needle-shaped crystals on the micrometre scale, whereas the irregular bar shape was observed for HBP. Transmission electron microscopy images show that both guest molecules formed nano vesicles with α-CD and formed nano rods with β-CD.     

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.     

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-as-sembled monolayers (SAMs) on gold surface were investigated by electrospray tandem ionization mass spectrometry (ESI-MS″) and cyclic voltammetry, respectively. The interfacial electrochemical response of the SAMs is related to the way in which the inclusion complexes formed.     

Synthesis of 4′-substituted 2′-deoxy-4′-thiocytidines and its evaluation for antineoplastic and antiviral activities

4′-Azido- (7), 4′-C-fluoromethyl- (8) 4′-C-ethynyl- (9) and 4′-C-cyano- (10) 2′-deoxy-4′-thiocytidines have been synthesized. In this study, it was found that the isolated yield of 4′-thiouracil nucleoside 13 in a Lewis acid-promoted Vorbrüggen-type glycosidation utilizing 12 was better than that of the electrophilic glycosidation reaction between silylated uracil and 11. This improved result prompted us to perform the glycosidation utilizing 36 and 43 for the synthesis of 37 and 44. Introduction of the azido group was carried out by nucleophilic substitution in the 4′-benzoyloxy derivative 22a. On the other hand, 9 and 10 were synthesized by way of the chemical manipulation of the hydroxymethyl group at the 4′-position of 46.Evaluation of the antineoplastic activity of 2 and 7–10 against human B-cell (CCRF-SB) and T-cell leukemia (Molt-4) cell lines revealed that 4′-azido- (7) and 4′-C-fluoromethyl- (8) derivatives exhibited cytotoxic activity whereas no cytotoxicity was observed in the 4′-C-ethynyl- (9) and 4′-C-cyano- (10) derivatives as well as the parent compound 2. Compound 7 was also found to possess promising antiviral activity against VZV and HSV-1 without any cytotoxity against HEL host cells. It is noteworthy that 7 exhibited potent inhibitory activities against the thymidine kinase-deficient (TK^?) mutant of VZV and HSV-1.     

Colorimetric determination of the activity of acetylcholinesterase and its inhibitors by exploiting the iodide-catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine by hydrogen peroxide

We describe a sensitive and selective colorimetric method for the determination of the activity of the enzyme acetylcholinesterase (AChE) and its inhibitors. Detection is based on the fact that acetylthiocholine iodide (ATCI) catalyzes the oxidation of the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by H₂O₂ to form a blue product (ox-TMB) with an absorption peak at 652 nm, but that oxidation is suppressed if ACTI previously is hydrolyzed by AChE to form thiocholine which decolorizes ox-TMB. In the presence of inhibitor, the activity of AChE is inhibited, thereby inducing the recovery of the blue coloration. Based on these findings, a highly sensitive method is developed for the determination of AChE and its inhibitors. The assay only requires mixing of buffer, solutions of ATCI, TMB, H₂O₂ and a sample containing AChE and photometric measurement. It works in the 0.05 to 5 mU?mL^?1 enzyme activity range and has a detection limit as low as 30 μU?mL^?1. The inhibitor neostigmine causes 50 % enzyme inhibition in 14.5 nM concentration. This analytical system has a wide scope in that it may be applied to the determination of the activity of various other hydrolases with proper substrates.

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Graphical abstract The blue product formed by the iodide-catalyzed oxidation of 3,3′5,5′-tetramethylbenzidine (TMB) by hydrogen peroxide is decolorized if acetylthiocholine iodide (ATCI) is hydrolyzed by acetylcholinesterase (AChE) to form thiocholine. If, however, AChE is inhibited, color formation will take place again.

     

Study of the fluorescence of 9,9′-bianthryl in polyvinylalcohol and in polyvinylchloride at 300 K and 80 K

By UV-vis spectroscopy and use of the polarization of the emission, we show that the 9,9′-bianthryl (9,9′BA) symmetrical molecule exhibits an induced fluorescence in polyvinylalcohol (PVA) by hydrogen bonding of the type OH⋯π which depends on considered temperature. This anomalous behaviour does not occur when this molecule is included in a polyvinylchloride, aprotic polymer.     

Determination of selectivity of HPLC systems by correspondence factor analysis

Correspondence factor analysis （CFA） was employed to study the selectivity of 14 HPLC systems. The tested LC systems were classified as reversed-phase （RP）, ion-exchange （IE） and hydrophilic interaction chromatography （HILIC） modes. It was found that the retentions of the hydrophilic solutes on HILIC column were significantly influenced by the second-order effects besides their hydrophilic properties. Organic modifiers and residue silanol groups on silica surface both participated in retention. HypersilTM amino column performed separation in the HILIC mode at appropriate conditions, and its retention mechanism was more similar to that of HILIC silica column than that of HILIC column coating poly（aspartamide） groups.