Synthesis of γγγ-trifluorocarbonyl compounds

γγγ-Trifluorocarbonyl compounds are easily obtained in a good yield by introduction of the 1,1,1-trifluoroethyl moiety (CF₃-CH₂-) on the -methylene group of a ketone.     

Preparation and enantiomer separation behavior of selectively methylated β-cyclodextrin-bonded stationary phases for high performance chromatography

Native and three selectively methylated β-cyclodextrin (β-CD)-bonded stationary phases without an unreacted spacer arm for liquid chromatography were prepared, where heptakis(2-O-methyl)-β-CD, heptakis(3-O-methyl)-β-CD and heptakis(2,3-di-O-methyl)-β-CD were used as the methylated β-CDs. The enantiomer separation abilities of the resulting β-CD stationary phases for 12 pairs of dansylamino acid enantiomers and six pairs of N-3,5-dinitrobenzoyl amino acid methyl esters as model solutes were investigated. The effects of pH and methanol content of the mobile phase on the retention and resolution were examined to optimize the mobile phase conditions. The optimum resolution for the dansylamino acids was achieved using a mobile phase consisting of 1.0% triethylammonium acetate buffer (pH 5.0)–methanol (v/v 4/6) on the β-CD stationary phase. Heptakis(3-O-methyl)- and heptakis(2,3-di-O-methyl)-β-CD-bonded stationary phases showed little enantiomer separation abilities for the dansylamino acids. The heptakis(2-O-methyl)-β-CD-bonded stationary phase exhibited no enantioselectivities for those solutes.

For the N-3,5-dinitrobenzoyl amino acid methyl esters, the optimum resolution was achieved using a mobile phase consisting of 1.0% triethylammonium acetate buffer (pH 5.0)–methanol (v/v 9/1) on a heptakis(2-O-methyl)-β-CD stationary phase. The heptakis(2,3-di-O-methyl)-β-CD-bonded stationary phases exhibited no enantioselectivities for the N-3,5-dinitrobenzoyl amino acid methyl esters. β-CD and heptakis(3-O-methyl)-β-CD-bonded stationary phases had no enantiomer separation abilities for those solutes except for the N-3,5-dinitrobenzoyl phenylalanine methyl ester.     

A spectrochemometric approach to tautomerism and hydrogen-bonding in 3-acyltetronic acids

3-Acyltetronic acids bearing different 3- and 5-substituents have been examined focussing on tautomerism and inter- and intramolecular hydrogen-bonding properties of these β,β′-tricarbonyl compounds in solution as well as in the solid state. Spectroscopic methods like NMR, IR, Raman-spectroscopy as well as X-ray diffractometry and MAS-NMR for the solid state have been applied. In a solution of CDCl₃, the acids exist as cis/trans pair both involving the 3-acyl group in a ratio 60/40. The pair also involving the carbonyl group at C-4 is tautomeric and the most abundant, whereas the other isomer only shows one form with an exo-cyclic double bond. NMR and IR measurements are in agreement. In the solid state, only one of the four possible tautomers is found. DFT-calculations on the B3LYP/6-31G** level helped to verify the assignment of the IR- and NMR-spectra and yielded an estimation of the relative thermodynamic stabilities of the tautomers of several 3-acyltetronic acids. Low temperature NMR experiments gave an insight into the equilibria. Deuterium isotope effects on the ¹³C NMR chemical shifts have been observed for 5,5-dimethyl 3-pivaloyltetronic acid at low temperature in order to examine the fast internal equilibria.     

The direct synthesis of dimethyl ether from syngas over hybrid catalysts with sulfate-modified γ-alumina as methanol dehydration components

A series of γ-Al₂O₃ samples modified with various contents of sulfate (0–15 wt.%) and calcined at different temperatures (350–750 °C) were prepared by an impregnation method and physically admixed with CuO–ZnO–Al₂O₃ methanol synthesis catalyst to form hybrid catalysts. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the prepared hybrid catalysts under pressurized fixed-bed continuous flow conditions. The results revealed that the catalytic activity of SO₄²⁻/γ-Al₂O₃ for methanol dehydration increased significantly when the content of sulfate increased to 10 wt.%, resulting in the increase in both DME selectivity and CO conversion. However, when the content of sulfate of SO₄²⁻/γ-Al₂O₃ was further increased to 15 wt.%, the activity for methanol dehydration was increased, and the selectivity for DME decreased slightly as reflected in the increased formation of byproducts like hydrocarbons and CO₂. On the other hand, when the calcination temperature of SO₄²⁻/γ-Al₂O₃ increased from 350 °C to 550 °C, both the CO conversion and the DME selectivity increased gradually, accompanied with the decreased formation of CO₂. Nevertheless, a further increase in calcination temperature to 750 °C remarkably decreased the catalytic activity of SO₄²⁻/γ-Al₂O₃ for methanol dehydration, resulting in the significant decline in both DME selectivity and CO conversion. The hybrid catalyst containing the SO₄²⁻/γ-Al₂O₃ with 10 wt.% sulfate and calcined at 550 °C exhibited the highest selectivity and yield for the synthesis of DME.     

Theoretical and experimental study of the inelastic neutron scattering spectra of β-5-Nitro-2,4-dihydro-3H-1,2,4-triazol-3-one

The inelastic neutron scattering (INS) spectra of β-5-Nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (β-NTO) are presented to 1400 cm⁻¹. The β-NTO vibrational frequencies observed differ considerably from the -NTO vibrational frequencies and normal mode frequency calculations for the isolated molecule. The INS spectrum contains detail unobserved in the previous IR studies, including combinations and overtones of the phonon and internal modes of β-NTO. The INS spectra are compared with periodic DFT calculations to show that the periodic DFT results correctly predict the solid-state molecular vibrational frequencies.     

NIR surface enhanced Raman spectroscopy and bands assignment by DFT calculations of non-natural β-amino acids

FT-Raman and NIR surface-enhanced Raman (SER) spectroscopies have been applied to the vibrational characterization of non-natural β-amino acids, 3-amino-3-(furan-2yl)-propionic acid and 3-amino-3-[(5-benzothiazole-2yl)-furan-2yl]-propionic acid. Semiempirical and density-functional theory (DFT) calculations on both amino acids in their zwitterionic forms have been performed in order to find the optimized structure and to compute the vibrational spectra. The NIR SER spectra in silver hydrosol and Ag-coated filter paper have been recorded, compared and analyzed. Good SER spectra were obtained at the pH values where dipolar ion structures are present proving the chemisorption of β-amino acid molecules on the silver surface via positively charged group. The carboxylate anion of both β-amino acids are parallel oriented, whereas the plane of rings is oriented perpendicular to the silver surface.     

Optical properties tuning of quantum-well lasers and photodiodes through γ-ray irradiation

Alterations of device characteristics as a result of γ-ray irradiation of quantum well lasers are different from those of heterostructure bulk lasers with respect to optical emission properties. We propose that these irradiation effects may be caused by structural changes in the quantum layers, due to an atomic displacement and migration between layers and due to changes in the degree of strain between the layers. This affects the layers’ atomic composition, which changes the band-gap energy levels and the refraction indexes, and, as a result, the carrier and optical confinements, respectively. The changes in optical radiation characteristics brought about by γ-ray irradiation are desirable ones for utilization in most optical fiber communication systems.     

Cu(I)-assisted carbon---carbon bond forming reactions of γ,γ-dialkoxyallylic zirconium species: a new versatile homoenolate equivalent of propionate

In the presence of CuCN, reaction of γ,γ-dialkoxyallylic zirconium species 1 with acyl chloride or allylic phosphates proceeded at the -position of 1 to give alkanoates 3 after aqueous work-up. The ketene dialkylacetal moiety in the coupling products 2 can be used for further bond forming reaction with electrophiles such as nitrosobenzene, nitrostyrene or trichloroacetylisocyanate.     

Micro-structural optimization of supported γ-alumina membranes

The micro-structural integrity of meso-porous inorganic membranes is of critical importance in their prolonged application. Inspection by transmission electron microscopy of state-of-the-art γ-alumina membrane cross-sections, made by focused ion beam milling, reveals structural defects which adversely affect performance, reproducibility, and lifetime. It is shown that the use of macro-porous supports with a smooth, defect-free deposition surface for membrane dip coating, in combination with purified precursor sols and clean processing, leads to major improvements in micro-structural homogeneity and properties of the membranes. Large particle contaminants/agglomerates can be effectively removed from precursor sols by high-speed centrifugation or ultrasound-assisted screening. While centrifugation is the most practical method for routine use, filter screening provides a more complete removal of agglomerates and larger particles (>80 nm Ø). Application of the purified membrane precursor sols results in membranes in which connected pore defects (pinholes) are no longer detectable for a membrane thickness of >500 nm thick. The almost complete absence of connected pinholes, obtained with improved membrane processing, is demonstrated by near-100% retention of CaCl₂ in aqueous solution by nano-filtration. The γ-alumina processing experience, collected in our group in the years 2002–2006, is accumulated in a 34-step processing protocol for γ-alumina membranes with a >500 nm single layer thickness.     

Specific adsorption of halogen anions on hydrous γ-Al2O3

The paper reports results of a study on the specific adsorption of F⁻, Cl⁻, Br⁻, I⁻, ClO₃⁻, BrO₃⁻, IO₃⁻ and IO₄⁻ on hydrous γ-Al₂O₃. The isotherms of the anion adsorption and the adsorption dependencies on pH and the ionic strength of the solution have been determined under the equilibrium conditions. According to the degree of affinity to γ-Al₂O₃, the anions can be ordered as: I⁻3⁻−−3⁻3⁻4⁻−. It has been established that the sorption of IO₄⁻ and F⁻ involves the formation of surface complexes in the inner co-ordination sphere, whereas that of Cl⁻, Br⁻, I⁻, ClO₃⁻, BrO₃⁻ and IO₃⁻ takes place through formation of ion pair complexes in the outer co-ordination sphere. In the dynamic system, the exchange isoplanes and elution curves have been determined for selected anions on columns filled with Al₂O₃. It has been shown that γ-Al₂O₃ can be used for isolation and concentration of IO₃⁻ from natural waters in order to decrease the limit of the ions determination to 2 μg l⁻¹. Using differential pulse voltammetry (DPV), after isolation and concentration on γ-Al₂O₃, the content of iodates has been determined in mineral, marine and tap water doped with these ions.     

Resistance properties of a macroporous silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide-impregnated polymeric adsorption material against nitric acid, temperature and γ-irradiation

The resistance of a novel silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric adsorption material (TODGA/SiO₂-P) against nitric acid, temperature and γ-irradiation had been investigated. The adsorption property of the treated TODGA/SiO₂-P was evaluated by a 3 M HNO₃ solution containing 0.01 M Nd(III). It was found that both 3 and 0.01 M HNO₃ concentrations did not decrease the stability of TODGA/SiO₂-P at 25°C. The quantity of TODGA leaked from TODGA/SiO₂-P was equivalent to its solubility in the corresponding HNO₃ aqueous solution. The effect of 3 M HNO₃ on the leakage of TODGA at 80°C was significantly higher than that in 0.01 M HNO₃ as well as in all cases at 25°C. The amount of Nd(III) adsorbed towards the treated TODGA/SiO₂-P was determined in the range of 0.143–0.148 mmol/g for the HNO₃ concentration effect and 0.142–0.0506 mmol/g for the temperature effect. γ-Irradiation showed a more noticeable destruction effect on TODGA/SiO₂-P. The content of TODGA leaked increased with an increase in the γ-irradiation dose (ID) from 1.06 to 3.72 MGy in terms of the linear equation [TODGA]=794.5ID+84.0. The amount of Nd(III) adsorbed onto the irradiated TODGA/SiO₂-P decreased rapidly from 0.134 to 0.0438 mmol/g, which was lower than 0.153 mmol/g, the adsorption of fresh TODGA/SiO₂-P for Nd(III), according to the equation Q_Nd(III)=−0.0301ID+0.160, showing that a large quantity of TODGA leaked from TODGA/SiO₂-P. The adsorbed amount of Nd(III) decreased obviously in this order: the HNO₃ concentration effect, temperature effect and γ-irradiation.     

Naturally occuring lactones and lactames—V: Halogenated β-keto esters as starting materials for the synthesis of tetronic acids

In an effort to improve and simplify the synthetic route to tetronic acids 15 differently substituted β-keto esters were investigated as potential starting materials. The β-keto esters were brominated and cyclised with 2·5 N KOH as cyclising agent. Tetronic acid and seven derivatives including the naturally occuring carolinic acid were obtained. In a number of cases products arising from a Favorskii rearrangment were isolated. The NMR spectroscopic data are discussed.     

Convenient method for the kinetic resolution of β-aminoalcohols

A variety of easily removable protecting groups were tested in the kinetic resolution of N-protected β-aminoalcohols using chiral catalysts derived from N-4′-pyridinyl--methyl proline. The trifluoroacetyl group was the most promising protecting group as it gave the highest selectivities with all alcohols tested and can easily be removed without loss of enantiomeric excess. This strategy constitutes a convenient method for the kinetic resolution of β-aminoalcohols.     

Synthesis and characterization of an ultrathin polyion complex membrane containing β-cyclodextrin for separation of organic isomers

An ultrathin polyion complex (PIC) layer containing β-cyclodextrin (β-CD) was formed on the surface of a charged base membrane. Thus, a positively charged copolymer containing β-CD was synthesized by the radical copolymerization of β-CD monomer and allylamine, and was used to modify the surface of a Nafion membrane containing negatively charged fixed ions. Electron spectroscopy for chemical analysis (ESCA) confirmed the presence of the copolymer on the surface of the Nafion membrane due to the formation of a PIC layer. The ability of the membrane to separate organic isomer mixtures was tested by the pervaporation technique, using butanol isomer mixtures as the feed model. The membrane exhibited a good selectivity toward butanol isomers, indicating the effectiveness of β-CD as a selective fixed carrier for the isomers.     

3-butenyl esters as convenient protecting groups for carboxylic acids

Carboxylic acids were protected as their corresponding 3-butenyl esters. Deprotection was carried out via ozonolysis and β-elimination of the resultant 3-acyloxypropanal.     

Structural determinants of steroids for cytochrome P450 3A4-mediated metabolism

Cytochrome P450 3A4 (CYP3A4), a major member of cytochrome P450 isoenzymes, metabolizes the majority of steroids in 6β-position. For the purpose of determining requisite structural features of a series of structurally related steroids for CYP3A4-mediated metabolism, three-dimensional pharmacophore modeling as well as electrotopological state map were conducted for 15 steroids. Though prior studies speculated that the chemical reactivity of the allylic 6β-position might have a greater influence on CYP3A4 selective 6-hydroxylation than steric constraints in the enzyme, our results reveal that for CYP3A4 steroidal substrates, it is not the chemical reactivity of atoms at 6β-site, but the pharmacophoric features, i.e. the two hydrophobic rings together with two H-bond donors, that act as the key factors responsible for determining the CYP3A4 selective 6-hydroxylation of steroids.     

Interaction between β-cyclodextrin and ionic liquids in aqueous solutions investigated by a competitive method using a substituted 3H-indole probe

We report herein the interaction of three kinds of ionic liquids, i.e., 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF₆), 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄) and 1-butyl-3-methylimidazolium chloride (bmimCl) with β-cyclodextrin (β-CD) using 2-(p-aminophenyl)-3,3-dimethyl-5-carboethyoxy-3H-indole (1) as a fluorescent probe through a competitive method. The formation of the 1:1 (guest:host) inclusion complex was suggested and the association constants at different temperatures were estimated, from which the thermodynamic parameters ΔG^Θ, ΔH^Θ and ΔS^Θ were also obtained. The negative entropy and enthalpy changes indicated that the formation of above inclusion complexes was entropically unfavorable and enthalpy-driven. Conductivity measurements were also employed to study above systems. The results showed agreement with those based on the competitive method. Furthermore, through NMR, the location of anions in the system of ILs and β-CD was investigated. We suggested that the anion was accommodated to a great extent by the cavity forming ion pair with imidazolium cation which was totally in the cavity of β-CD. The above work demonstrated that molecule 1 is a very sensitive fluorescence probe for studying the interaction of a non-fluorescent guest with cyclodextrins.     

Enthalpies of combustion and formation of 3-formylchromones

The enthalpies of combustion of 3-formylchromone (3F), 3-formyl-6-methylchromone (3F6M) and 3-formyl-6-isopropylchromone (3F6I) were determined by combustion calorimetry. The molar combustion energies () of the 3F, 3F6M and 3F6I are: −(4452.4 ± 1.8), −(5115.6 ± 2.7) and −(6411.4 ± 2.5) kJ mol⁻¹, respectively. The formation enthalpies in the crystalline state () are: −(340.2 ± 2.2), −(355.1 ± 3.1) and −(415.5 ± 3.0) kJ mol⁻¹, respectively.s     

The research of using Co-60 γ ray to sterilize different mediums for edible fungus

The present experiment has been carried out by using different dosage of Co—60 γ ray for radiation sterilization of five kinds of cultural materials of edible fungus, The results indicated that sterilization dosage of sawdust is 22 kGy. that of cotton—seed shell and the rest are 26 kGy. We conclude that using Co-60 γ ray to sterilize the cultura 1 materials of edible fungus is a secure and saving labor and energy new method which could sterilize thoroughly.     

Synthesis of aryl β-D-glucopyranosides and aryl β-D-glucopyranosiduronic acids

Tetra-O-benzyl--D-glucopyranosyl bromide in dichloromethane reacts stereospecifically with solutions of phenols in aqueous sodium or potassium hydroxide, in the presence of phase transfer catalysts, to give good yields of tetra-O-benzyl aryl-β-D-glucopyranosides which are converted into the corresponding aryl β-D-glucopyranosiduronic acids by sequential catalytic debenzylation and catalytic oxidation.