Stereoselective Synthesis of γ-(Acyloxy)carboxylic Acids and γ-Lactones Featuring the Switch of Stereopreference of Candida antarctica Lipase B in Sodium γ-Hydroxycarboxylate Homologues

Scalable protocols of straightforward synthesis of enantiomeric γ-(acyloxy)carboxylic acids and γ-lactones are presented. The key step is lipase-catalyzed stereoselective acylation of γ-hydroxycarboxylic acid sodium salt in organic solvent followed by acidification of the product, extraction and acidic relactonization of the unreacted enantiomer. The mixture of γ-(acyloxy)carboxylic acid and γ-lactone is separated either by extraction with solution of sodium bicarbonate or by distillation. A switch of enantioinduction of Candida antarctica lipase B along homologous nucleophiles from R configuration of γ-hydroxyhexanoic acid salt to S configuration of the C7 and longer-chain homologues has been disclosed. Both enantiomers of γ-(acyloxy)pentanoic acids; γ-(acetyloxy)octanoic and -nonanoic acids with S configuration; [(1S,5R)-5-(chloroacetyloxy)cyclopent-2-en-1-yl]acetic acid and enantiomeric γ-lactones derived from them were prepared with e. r. >98.5/1.5. The rates of acylation of C5 to C9 homologous salts differ by three orders of magnitude but remain applicable for preparative synthesis by variation of the enzyme loading and reaction time.     

γ-Carbolines and their hydrogenated derivatives 3.* Hydrogenated derivatives of γ-carbolines: chemical and biological poperties (Review)

Published data on the chemical transformations and biological properties of dihydro-, tetrahydro-, and hexahydro-γ-carbolines are reviewed.     

Determination of Promedol (Trimeperidine) and Ketamine in Blood Using Gas Chromatography–Mass Spectrometry

A procedure was developed for the gas-chromatographic determination of promedol (trimeperidine) and ketamine in whole blood with mass-selective detection. The detection limit for trimeperidine and ketamine in blood is 0.05 g/mL. The analytical range is 0.1–5.0 g/mL. The maximum within-series errors in the determination of the studied compounds are no higher than 14.1% for concentrations of 0.10 g/mL and 7.47% for concentrations of 1.0 g/mL. The maximum between-series relative errors are 5.75% for concentrations of 0.10 g/mL and 2.7% for concentrations of 1.0 g/mL. The procedure can be used in toxicological and clinical analyses.     

Measurement of neutron-capture cross section and capture γ-ray spectrum of 105Pd(n,γ)106Pd reaction

We measured the neutron-capture cross section and the capture γ-ray spectrum of the ¹⁰⁵Pd(n,γ)¹⁰⁶Pd reaction with about 550 keV neutrons produced from the ⁷Li(p,n)⁷Be reaction at a 3-MV Pelletron accelerator. The capture yields of the palladium or gold sample were obtained by applying a pulse-height weighting technique to the corresponding net capture γ-ray pulse-height spectra. The neutron-capture cross section of the ¹⁰⁵Pd(n,γ)¹⁰⁶Pd reaction was determined with errors less than 5 % by using the standard capture cross sections of ¹⁹⁷Au. The neutron-capture γ-ray spectrum was obtained by unfolding the observed capture γ-ray pulse-height spectra. Theoretical calculations of cross sections and γ-ray spectra with the Empire code have been performed by utilizing the Hauser-Feshbach statistical model. The calculated results have a good agreement with present measurements.     

Spectrophotometric Simultaneous Determination of Zinc(II), Manganese(II) and Iron(II) in Pharmaceutical Preparations Using OSC-PLS

The purpose of this paper is to develop a fast and sensitive spectrophotometric method for the simultaneous determination of zinc(II), manganese(II) and iron(II) in pharmaceutical preparations. The method presented in this work is based on the well-known reaction of these ions with 4-(pyridylazo)resorcinol (PAR)1. The application of quantitative chemometric methods, particularly PLS to multivariate chemical data is becoming more widespread owing to the availability of digitized spectroscop…     

Detailed Hydrocarbon Class Composition Analysis and Trace Level BTEX Estimation in Raffinate Column Bottom (RCB) Using GC×GC–TOFMS

A two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOFMS) method was developed for the hydrocarbon class composition analysis and benzene, toluene, ethylbenzene, and xylene (BTEX) estimation of raffinate column bottom (RCB), which is generated as a by-product from linear alkyl benzene (LAB) plants. The molecular level characterization of RCB is important to generate value-added products for the petrochemical industry. GC×GC–TOFMS was found to be an excellent tool for estimation of hydrocarbon class composition (paraffins, naphthenes, monoaromatics, diaromatics, and polyaromatic hydrocarbons) and trace level BTEX in a single run. The hydrocarbon class composition was validated with the standard method based on HPLC (ASTM D6591) and good correlation was obtained. Finally, RCB is anticipated to be a useful nonhazardous safe by-product which could be used further for generating added value.     

Electron paramagnetic resonance (EPR) study of γ-radiation-induced radicals in 1,3,5-trithiane and its derivatives

Radicals formed in γ-irradiated 1,3,5-trithiane (TT) and its three derivatives, α- and β-2,4,6-trimethyl-1,3,5-trithiane (α-TMT and β-TMT), and 2,4,6-trimethyl-2,4,6-triphenyl-1,3,5-trithiane (TMTPT), were studied by the electron paramagnetic resonance (EPR) method in the solid state. The sulfur radical cations (>S^+•) were identified in all compounds at 77 K. In TT and its two derivatives, α-TMT and β-TMT, the >S^+• decay via deprotonation-forming C-centered radicals. Further increase of temperature up to 293 K results in the appearance of thiyl-type radicals (RS^•). In TMTPT, the >S^+• are stable up to 250 K. They formed the intermolecularly three-electron-bonded dimeric radical cations (S∴S)⁺ while RS^• radicals were not observed. Some of the radical assignments and their EPR parameters (g and a hyperfine splittings) obtained support from the DFT calculations.     

Elucidation of the structure of poly(γ-benzyl-l-glutamate) nanofibers and gel networks in a helicogenic solvent

The synthesis, characterization, self-assembly, and gel formation of poly(γ-benzyl-l-glutamate) (PBLG) in a molecular weight range from ca. 7,000–100,000 g/mol and with narrow molecular weight distribution are described. The PBLG is synthesized by the nickel-mediated ring-opening polymerization and is characterized by size-exclusion chromatography coupled with multiple-angle laser light scattering, NMR, and Fourier transform infrared spectroscopy. The self-assembly and thermoreversible gel formation in the helicogenic solvent toluene is investigated by transmission electron microscopy, atomic force microscopy, small-angle X-ray scattering, and synchrotron powder X-ray diffraction. At concentrations significantly below the minimum gelation concentration, spherical aggregates are observed. At higher concentrations, gels are formed, which show a 3D network structure composed of nanofibers. The proposed self-assembly mechanism is based on a distorted hexagonal packing of PBLG helices parallel to the axis of the nanofiber. The gel network forms due to branching and rejoining of bundles of PBLG nanofibers. The network exhibits uniform domains with a length of 200?±?42 nm composed of densely packed PBLG helices.      

Stereoselective syntheses of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones and naturally occurring lipid guggultetrol

γ-Oxo-butyramides derived from tartaric acid serve as excellent precursors for the synthesis of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones and for the synthesis of tetrols containing three contiguous stereogenic centres. The methodology presented here is general for the synthesis of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones. Utility of the chiral building block was demonstrated by the synthesis of naturally occurring lipid guggultetrol.     

Highly Sensitive Determination of Traces of Co(II) in Pharmaceutical and Urine Samples Using Kinetic–Spectrophotometric Method

Abstract

A high sensitive, accurate and simple kinetic method has been developed for determination of trace of Co(II) ions, based on its strongly catalytic effect in the reaction oxidation of disodium-6-hydroxy-5-[(4-sulfophenyl)azo]-2-naphtalenesulfonic acid (artificial color, Sunset Yellow FCF, E110 in text selected as SY) by hydrogen peroxide in borate buffer at pH of 9.5, by monitoring the rate of disappearance of SY. Reaction rate was monitored spectrophotometrically, at λ_max of the SY at 478.4 nm. The optimum operating conditions regarding reagents concentration and temperature were established. The tangent method was adopted for constructing the calibration curve, which was found to be linear over the concentration range 1.18–17.67 ng ml^?1 and 17.67–58.90 ng ml^?1 of Co(II). The limit of detection (3σ) is 0.15 ng ml^?1, and limit of quantification (10σ) is 0.5 ng ml^?1. The effects of the other ions on the reaction rate were determined for an assessment of the selectivity of the method. The developed kinetic procedure was successfully applied for the determination of Co(II) in pharmaceutical and urine samples. The unique features of this procedure are that the determination can be performed at room temperature, and the analysis time is short. The newly developed method is high sensitive, simple, inexpensive and efficient for use in the analysis of a large number of samples.     

Effect of the Composition of Ethanol–Water Mixtures on the Properties of Oxide (Zn-Zr-Si) and Zeolitic (Ta/SiBEA) Catalysts in the Production of 1,3-Butadiene

Theoretical and Experimental Chemistry - The reasons for the deactivating effect of water on the conversion of ethanol to 1,3-butadiene in the presence of Zn-Zr(La)-Si oxide and Cu(Ag, Zn)/Ta/SiBEA...     

Coordination Polymers Formed by the Reactions between Zn(II), Co(II), and Ni(II) Cimantrenates and γ,γ'-Dipyridyl in Methanol

Reactions between methanol adducts of Zn(II), Co(II), and Ni(II) cimantrenates and γ,γ′-dipyridyl in methanol have been found to result in the formation of 1D coordination polymers, whose structure is governed, according to X-ray diffraction data, by the nature of the transition metal.     

Improvement in Adhesion between Ethylene–Propylene–Diene Terpolymer (EPDM)-based Elastomer and Polyurethane Coating Using Epoxy–Polysulfide Copolymer As Adhesion Promoter

Epoxy–polysulfide copolymer as an adhesion promoter was added to ethylene–propylene–diene terpolymer and the effect of maleation of terpolymer with maleic anhydride on its adhesion to polyurethane coating was studied. The results show that using epoxy-polysulfide copolymer as the adhesion promoter cause a significant improvement in adhesion of terpolymer to polyurethane coating. The contact angle of the water reduced from 88° for the unmodified terpolymer to 65° for the maleated terpolymer containing 10 phr of epoxy–polysulfide copolymer. Peel strength was also increased from 0.2 N/mm for the unmodified terpolymer to 1.12 N/mm for the above-mentioned modified elastomer. Effect of the composition of the polymer blends on the loss tangent and storage modulus was studied to evaluate phase separation and crosslink density. The improvement of adhesion to polyurethane occurred without phase separation, which was further confirmed by the results of the mechanical and morphological investigations.     

Triazole derivatives as analytical reagents. Part V. Analytical studies of β-resorcylazomercaptotriazole (METRIAREZ-β) and γ-resorcylazomercaptotriazole (METRIAREZ-γ) acids

METRIAREZ- and -, two new derivatives of 5-mercapto-1,2,4-triazole with - and -resorcylic acids have been synthesized and their physicochemical and chelating properties determined. With metal ions havingp andd electrons they form water-soluble coloured chelates at L M molar ratios of 1 1 with Cu²⁺ and Pb²⁺ ( and ), Hg²⁺ and Zn²⁺ () and Cd²⁺, In³⁺ and Bi³⁺ () and 2 1 with Fe³⁺, Fe²⁺, Co²⁺ and Ni²⁺ ( and ) and Zn²⁺ (). The chelates are non-extractable by organic solvents. The stability constants of these complexes, as well as their spectrophotometric sensitivity and extinction coefficients were determined. Iron and zinc in multivitamin tablets were determined spectrophotometrically using the ligands.     

Aggregation Behavior of Poly(ethylene glycol)-block-poly (γ-benzyl L-glutamate)-graft-poly(ethylene glycol) Copolymer and its Blends with Poly(γ-benzyl L-glutamate) Homopolymer in Mixed Solvents

Poly(ethylene glycol)-block-poly(γ-benzyl L-glutamate)-graft-poly(ethylene glycol) (PEG-b-PBLG-g-PEG) copolymer was synthesized by the ester exchange reaction of PBLG-block-PEG copolymer with mPEG. The self-association behaviors of PEG-b-PBLG-g-PEG and its blends with PBLG homopolymer in the mixtures of ethanol and dimethylformamide (DMF) were investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), and viscometry. Effects of the introduction of PBLG homopolymer, the grafting ratio, and the DMF content on the self-association behaviors of PEG-b-PBLG-g-PEG copolymer in the mixtures of ethanol and DMF were mainly researched. It was revealed that PEG-b-PBLG-g-PEG copolymer could self-assemble to form polymeric micelles with a core-shell structure in various shapes from different preparation conditions. The critical micelle concentration (CMC) and the average particle diameter of the micelles formed by PEG-b-PBLG-g-PEG copolymer in the mixed solvents also changed with different preparation conditions.     

Intercalation of tris-(2,2′-bipyridyl) ruthenium (II) in α- and γ-zirconium phosphate: synthesis, thermal behaviour and X-ray characterization

Intercalation compounds such as the ruthenium trisbipyridyl complex in inorganic layered ion-exchangers (α- and γ-zirconium phosphate) have been synthesized using the batch method. There is no loss of bipyridyl ligand from the metal ion during the exchange of the ruthenium trisbipyridyl complex in these host matrices. The materials obtained are thermally stable up to ~330 °C (γ-phase) or ~380 °C (α-phase). The complex decomposition occurs in one or more steps and at ~600 °C the complex decomposition is complete. The X-ray patterns of ruthenium materials show a new phase with an increase in the interlayer distance with respect to the initial phase. Microanalysis measurements confirm the fact that the ruthenium complex is not modified when exchanged and the complex decomposition depends on its position in the host matrices.     

Kinetic study of decomposition for Co(II)- and Ni(II)-1,10-phenanthroline complexes intercalated in γ-zirconium phosphate

The thermal behaviour of the complexes formed in situ between the aromatic diamine 1,10-phenanthroline and the Co(II) and Ni(II) ions intercalated between the layers of γ-zirconium phosphate was studied by simultaneous TG/DSC techniques. The obtained materials show similar thermal behaviour: after a multi-step dehydration process they showed an oxidative decomposition in only one step. The kinetic study of the decomposition process was performed using both the model-free methods of Ozawa-Flynn-Wall and Kissinger. The former method provides a negligible dependence of activation energy on the degree of reaction α for both materials. Activation energies derived by the Kissinger method show a good agreement with the mean values derived by the Ozawa-Flynn-Wall method. The Arrhenius rate constants determined using also the pre-exponential factor values demonstrate that their thermal stability can be considered comparable, within the experimental uncertainty. Finally, a reliable method was applied to determine the model function from the best fit between the numerical dependence of the integral function g(α) vs. α and several theoretical model dependencies reported in literature for the most commonly used models. A Mampel first-order reaction model was selected to describe the thermal decomposition in both the materials studied.