Benzimidazole-based chromogenic chemosensor for the recognition of oxalic acid via counter ion displacement assay in semi-aqueous medium

An azo dye-coupled benzimidazole-based receptor 1 was synthesized and investigated as a receptor for metal ions in semi-aqueous medium. The receptor recognizes Cu²⁺ with high selectivity over other metal ions. The resultant complex 1·Cu²⁺ was found to selectively bind oxalic acid via counter ion displacement.     

A NOVEL SYNTHETIC APPROACH TO 4-SUBSTITUTED QUINAZOLINES

Abstract

A novel two-step synthetic method to prepare 4-(thienyl)quinazolines (8a and 8b) is described. The method is based on the simultaneous reductive cyclization of a nitro group β to the carbonyl group in ketones under Leuckart reaction conditions. The method has been found useful for the syntheses of the 4-substituted quinazolines.     

Novel biobased photo‐crosslinked polymer networks prepared from vegetable oil and 2,5‐furan diacrylate

Novel biobased crosslinked polymer networks were prepared from vegetable oil with 2,5‐furan diacrylate as a difunctional stiffener through UV photopolymerization, and the mechanical properties of the resulting films were evaluated. The vegetable oil raw materials used were acrylated epoxidized soybean oil (AESO), acrylated castor oil (ACO), and acrylated 7,10‐dihydroxy‐8(E)‐octadecenoic acid (ADOD). 2,5‐Furan dicarboxylic acid (FDCA), which can be synthesized through the oxidative dehydration of C6 sugars, was identified by the US Department of Energy as one of 12 priority chemicals for establishing the green chemistry industry of the future. 2,5‐Furan dimethanol (bis‐hydroxymethylfuran), which can be derived from FDCA, was used as a starting material to synthesize 2,5‐furan diacrylate, which was used as a biobased comonomer along with AESO, ACO, or ADOD to form photo‐crosslinked polymer networks. The synthesis of acrylate derivatives was confirmed using FT‐IR and ¹H‐NMR spectroscopic techniques. The composition of the reaction mixture was changed to obtain crosslinked polymer networks with various mechanical properties. The addition of 2,5‐furan diacrylate increased the tensile strengths of the polymer films by up to 1.4–4.2 times relative to those obtained without the addition. These fully biobased polymers derived from vegetable oil and sugar can be used as environmentally friendly renewable materials for various applications to replace the existing petroleum‐based polymers currently used. Copyright © 2013 John Wiley & Sons, Ltd.     

Proton-ionizable acyclic dibenzopolyethers and their polymers for use in selective lead(II) separation

Abstract

2,2′-[1,2-Ethanediylbis(oxy)]bisbenzoic acid (1), 2,2′-[oxybis(1,2-ethanediyloxy)]bisbenzoic acid (2), 1,2-[2′-(acetoxy)phenoxy] ethane (3), and 1,5-[2′-(acetoxy)phenoxy]-3-oxopentane (4) have been prepared for use in selective Pb(II) separation. The extraction of Pb(II) and Cu(II) from buffered aqueous solutions of varying pH into chloroform by 1–4 is examined in relation to their molecular structure. Compound 1 with an ethylene glycol spacer unit exhibits excellent extraction selectivity for Pb(II) over Cu(II). Lengthening the spacer group to a diethylene glycol unit diminishes the extraction efficiency and selectivity. For 3 and 4, extraction was inefficient due to low lipophilicity and solubility of the ligands in chloroform. Condensation polymerization of compounds 3 and 4 with formaldehyde in formic acid provides stable chelating resins 5 and 6 which contain both ion-exchange and polyether binding sites for metal complexation. Resin 5 with an ethylene glycol spacer group is found to be an effective chelating resin for Pb(II) separation. The sorption mechanism and selectivity are studied and compared with the commercially available iminodiacetic acid resin CR-10.     

Validation of an analytical LC-MS/MS method in human plasma for the pharmacokinetic study of atomoxetine

This study aimed to validate a sensitive and reliable analytical method for the pharmacokinetic study of atomoxetine in human plasma by liquid chromatography-electrospray ionization-tandem mass spectrometry. Metoprolol was used as an internal standard. After liquid-liquid extraction with methyl t-butyl ether, the supernatant was evaporated. The residue was then reconstituted and an aliquot was injected into the high performance liquid chromatographic system. Separation was performed on a Phenomenex Luna C₁₈ column (2.0 mm × 100 mm, 3 μm particles) with a mobile phase of 10 mM ammonium formate buffer: methanol = 10: 90 (v/v). Tandem mass spectrometry was performed in the electrospray ionization positive ion mode using the multiple reaction monitoring mode for quantification. The mass transition pairs of m/z 256 → 44 for atomoxetine and m/z 268 → 116 for the internal standard were used. The flow rate of the mobile phase was 0.25 mL/min and the retention times of atomoxetine and the internal standard were found to be 1.0 and 0.9 min, respectively. The calibration curve for atomoxetine was linear in the concentration range of 1–750 ng/mL (r ² = 0.9992) with a lower limit of quantification of 1 ng/mL. The mean accuracy for atomoxetine was 93–102%. The coefficients of variation (precision) in the intra- and inter-day validation for atomoxetine were 4.0–6.8 and 1.1–9.6%, respectively. The pharmacokinetic parameters of atomoxetine were evaluated after administration of a 40-mg single oral dose to twelve healthy male volunteers. The mean AUC_{0–24 h}, C _max, T _max and T _1/2 for atomoxetine were 1.9 ± 0.8 μg h/mL, 0.34 ± 0.11 μg/mL, 1.0 ± 0.5 h and 3.9 ± 1.3 h, respectively.     

Highly sensitive analysis of catecholamines by counter‐flow electrokinetic supercharging in the constant voltage mode

Electrokinetic supercharging is one of the most powerful sample‐stacking methods that combines field amplified sample injection and transient ITP. In counter‐flow electrokinetic supercharging, a constant counter pressure is applied during sample injection in order to counterbalance the movement of the injected sample zone. As a result, there will be a pronounced increase in the amount of sample injected and the portion of the capillary available for electrophoresis. In this report, counter‐flow electrokinetic supercharging optimization factors such as the electric field application in the constant voltage and constant current modes, the magnitude of counter pressure, and the terminating electrolyte concentrations were investigated. The enrichments obtained with a 30 min injection of 10 nM catecholamines in 5 mM terminating electrolyte solution in the constant voltage mode applying a counter pressure of 1.3 psi were 41000‐fold for dopamine, 50 000‐fold for norepinephrine, and 32 000‐fold for epinephrine, yielding detection limits of 1.3, 1.4, and 1.2 nM, respectively, with absorbance detection at 200 nm.     

A Biodegradable Polymersome Containing Bcl‐xL siRNA and Doxorubicin as a Dual Delivery Vehicle for a Synergistic Anticancer Effect

Combined cancer treatment via co‐delivery of siRNAs and an anticancer drug can be a promising strategy due to the synergistic effect of simultaneously minimizing gene/drug administration. In this study, Bcl‐xL siRNA and doxorubicin (DOX) are encapsulated into designed methoxy‐poly(ethylene glycol)‐block‐poly(D ,L ‐lactic acid) (mPEG‐b‐PLA) block copolymer polymersomes (PSomes). A study of the cytotoxicity of Bcl‐xL siRNA and DOX co‐encapsulated PSomes (CPSomes) shows more inhibited proliferation of MKN‐45 and MKN‐28 human gastric cancer cell lines than only gene‐ and drug‐loaded ones. Consequently, these results demonstrate that co‐delivery of genes and drugs using PSomes results in a synergistic efficacy and indicates the potential of PSomes as efficient nanocarriers for combined cancer therapy.

     

Selective Semihydrogenation of Alkynes on Shape‐Controlled Palladium Nanocrystals

A systematic study on the selective semihydrogenation of alkynes to alkenes on shape‐controlled palladium (Pd) nanocrystals was performed. Pd nanocrystals with a cubic shape and thus exposed {100} facets were synthesized in an aqueous solution through the reduction of Na₂PdCl₄ with L ‐ascorbic acid in the presence of bromide ions. The Pd nanocubes were tested as catalysts for the semihydrogenation of various alkynes such as 5‐decyne, 2‐butyne‐1,4‐diol, and phenylacetylene. For all substrates, the Pd nanocubes exhibited higher alkene selectivity (>90 %) than a commercial Pd/C catalyst (75–90 %), which was attributed to a large adsorption energy of the carbon–carbon triple bond on the {100} facets of the Pd nanocubes. Our approach based on the shape control of Pd nanocrystals offers a simple and effective route to the development of a highly selective catalyst for alkyne semihydrogenation.