The effect of heteroatom substitution of sulfur for selenium in glucosidase inhibitors on intestinal α-glucosidase activities

The synthesis of selenium analogues of de-O-sulfonated ponkoranol, a naturally occurring sulfonium-ion glucosidase inhibitor isolated from Salacia reticulata, and their evaluation as glucosidase inhibitors against two recombinant intestinal enzymes maltase glucoamylase (MGAM) and sucrase isomaltase (SI) are described.     

Pre‐concentration of trace amount of bisphenol A in water samples by palm leaf ash and determination with high‐performance liquid chromatography

Palm leaf ash was characterized and used as low‐cost adsorbent for solid‐phase extraction and preconcentration of bisphenol A (BPA) in real water samples. Analysis of BPA was carried out using HPLC involving Eurospher 100–5‐C₁₈ (25 cm × 4.5 mm, particle size 5 μm) column and water–acetonitrile (40:60, v/v) as mobile phase. The adsorption was achieved quantitatively at a pH of 6 with elution by 3 mL acetonitrile. The limits of detection and enrichment factor were 0.02 μg L^?1 and 333, respectively. Under optimum conditions the relative standard deviation (RSD) was 2% (n = 10). Comparison of qualification criteria of presented preconcentration procedure with other research indicated that palm leaf ash adsorbent was better than many of the adsorbents in terms of cost and reusability. Also, the limit of detection, precision and enrichment factor were comparable and even better than the previously reported methods. Finally, the efficiency of method was computed by determination of trace amounts of BPA in sea, river, mineral and tap waters with recoveries of 93.3–105.5% and RSDs of 0.61–3.12%.. Briefly, the developed solid‐phase extraction and Preparative layer chromatography (PLC) methods may be used for bisphenol A monitoring in any environmental water sample. Copyright © 2016 John Wiley & Sons, Ltd.     

Cesium Salt of Tungstosilicic Acid Fabricated by Nano-Casting Strategy: An Efficient Catalyst for the Three-Component Hosomi–Sakurai Reaction

Abstract

We have used SBA-15 silicas as hard templates for the nano-fabrication of Cs_1.8H_2.2SiW₁₂O₄₀ (CsHSiW) salt nanocrystal. The elimination by HF (or NaOH 90 °C) in the silica matrix from the composites occurred by a two-step reaction deposition of CsHSiW salt nanocrystal. The nano-casted CsHPW materials were characterized by several techniques: chemical analysis (atomic absorption, neutron activation analysis, and inductively coupled plasma) and spectroscopic methods (FT-IR spectrum, X-ray diffraction, transmission electron microscopy, and energy dispersive x-ray analysis measurement). In addition to the complete characterization of CsHSiW nanocrystal samples, their catalytic performances are shown for the three-component Hosomi–Sakurai reaction. The reaction proceeds efficiently under ambient conditions with good to excellent yields.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Immobilization of 1,4-Diazabicyclo[2.2.2]Octane (DABCO) over Mesoporous Silica SBA-15: An Efficient Approach for the Synthesis of Functionalized Spirochromenes

Immobilized 1,4-diazabicyclo[2.2.2]octane (DABCO) over mesoporous silica SBA-15 has been found to be an efficient heterogeneous base catalyst for the synthesis of biologically active functionalized spirochromene derivatives via three-component reaction of isatins/acenaphthoquinone, activated methylene reagents, and 1,3-dicarbonyl compounds in aqueous media. This ecofriendly protocol offers several advantages such as a cost-effective procedure with excellent yield, short reaction time, simple workup, recovery and reusability of catalyst, good functional group tolerance, and broad scope of usable substrates.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Dinuclear copper(II) complexes with ethylenediamine derivative and bridging oxalato ligands: solvatochromism and density functional theory studies

Two oxalato-bridged copper(II) complexes of formula, [Cu₂(L¹)₂(µ-ox)](NO₃)₂·H₂O, 1 and [Cu₂(L²)₂(µ-ox)](NO₃)₂·H₂O, 2 (ox = oxalato dianion, L¹ = N,N-dimethyl,N′-benzylethane-1,2-diamine, L² = N,N-diethyl,N′-benzylethane-1,2-diamine), have been synthesized and characterized by elemental analyses, spectroscopic (IR, UV–Vis) data and molar conductance measurements. The crystal structure of complex 1 was determined by X-ray diffraction analysis, revealing two centrosymmetric dinuclear units. The first consists of a [Cu₂(L¹)₂(µ-ox)(NO₃)₂] molecule, in which each Cu(II) center is in a square-pyramidal environment, providing two nitrogen atoms from the diamine-chelating ligands plus two oxygen atoms from the oxalate in the basal plane and an oxygen of the nitrate group in the axial position. The second unit [Cu₂(L¹)₂(µ-ox)(H₂O)₂](NO₃)₂ has a similar structure, but the apical sites are occupied by water ligands and the nitrate anions are free from coordination. Both complexes are solvatochromic. Their solvatochromism was investigated with different solvent parameter models using SPSS/PC and DFT methodology. The solvatochromic behaviors of the complexes were also explored by TD-DFT in ethanol and acetonitrile solvents. The calculated visible absorption spectra were in accord with the experimental results.     

Construction and Application of an Electrochemical Sensor for Simultaneous Determination of Cd(II), Cu(II) and Hg(II) in Water and Foodstuff Samples

By incorporation of synthesized magnetite nanoparticles (Fe₃O₄ NPs) coated with a new Schiff base into carbon paste electrode, a novel modified electrode was constructed for simultaneous determination of ultra trace amounts of Cd(II), Cu(II) and Hg(II). The complexation reaction of Schiff base with metal ions was studied spectrophotometrically. Under optimal conditions a detection limit of 0.20, 0.90 and 1.00 ng mL^?1 for Cd(II), Cu(II) and Hg(II), respectively, was obtained. We take the advantages of the proposed method for simple, rapid, sensitive and selective simultaneous determination of trace amounts of hazardous Cd(II), Cu(II) and Hg(II) in water and foodstuff samples.