Separation, characterization, and quantitation of process-related substances of the anti-hypertensive drug doxazosin mesylate by reversed-phase LC with PDA and ESI-MS as detectors

A simple and rapid reversed-phase liquid chromatography (LC) method with photodiode array (PDA) and electrospray ionization (ESI)-mass spectrometry (MS) as detectors was developed and validated to separate, identify, and quantitate the related substances of Doxazosin mesylate (DXZN) for monitoring the reactions involved during process development. The high-performance liquid chromatography profiles of related-substances of DXZN are used as fingerprints to follow the procedures used in the manufacturing units. The separation is accomplished on an Inertsil ODS-3 column with acetonitrile-ammonium acetate (10 mM, pH 4.0) as the mobile phase, using a gradient elution mode and monitoring the eluents by a photodiode array detector at 265 nm at ambient temperature. LC-ESI-MS-MS is used to identify the additional impurities formed during the synthesis. The identified impurities were synthesized and characterized by UV, Fourier transform-IR, 1H NMR, and MS data. The detection limits for the impurities are 0.74 - 4.14 x 10(-9) g, and the method is found to be suitable not only for the monitoring of synthetic reactions, but also for quality assurance of DXZN in bulk drugs and formulations.     

Total Synthesis of Kopsinitarine E

Kopsinitarines A–E are complex octacyclic caged Kopsia alkaloids with strained cage skeletons and a unique cyclic hemiaminal bridge that makes total synthesis challenging. Herein, we disclose the first total synthesis of kopsinitarine E. The key synthetic features include a SmI₂-mediated radical cascade cyclization and a subsequent semi-pinacol rearrangement to install the key carbocyclic skeleton, a chemoselective hydrosilyl amide reduction to construct the hemiaminal ether bridge, and an intramolecular Mannich reaction to establish the highly strained cage system.     

Microhardness studies on as‐grown (111) faces of some alkaline earth nitrates

Single crystals of Sr(NO₃)₂, Ba(NO₃)₂ and Pb(NO₃)₂ are grown from their aqueous solutions at a constant temperature of 35 °C by slow evaporation technique. Crystals of size 8 to 10 mm along one edge are obtained in a period of 10 days. Chemical etching technique has been employed to study the dislocations in these crystals. The dislocations are randomly distributed and the dislocation density is about 10⁴ to 10⁵ /cm². Microhardness studies are made on as–grown (111) faces of these crystals upto a load of 100 g. The hardness of the crystals increases with an increase in load and thereafter it becomes independent of the applied load. These results are discussed on the basis of reverse indentation size effect. Meyer index number n for these crystals is estimated at both low and high load regions. An analysis of hardness data of these crystals as well as some other cubic crystals like alums and alkali halates are discussed using Gilman–Chin parameter H_v/C₄₄, where H_v is the microhardness and C₄₄ is the shear constant. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Development and validation of a reversed-phase liquid chromatographic method for separation and simultaneous determination of COX-2 inhibitors in pharmaceuticals and its application to biological fluids

An isocratic reversed-phase high-performance liquid chromatographic method has been developed for separation and simultaneous determination of COX-2 inhibitors, viz., celecoxib, rofecoxib, valdecoxib, nimesulide and nabumetone, using 4-chloro-2-nitroaniline as internal standard. Good chromatographic separation was achieved using a reversed-phase Inertsil C(18) column with mobile phase consisting of methanol and 0.05% aqueous glacial acetic acid (68:32 v/v) using photodiode array (PDA) detector at 230 nm. It was validated with respect to accuracy, precision, linearity, limit of detection and quantification. The linearity range was found to be 1.0--20 microg/mL and the percentage recoveries were between 97.55 and 100.14. The method is suitable not only for the estimation of active ingredients in pharmaceutical dosage forms but also in vitro estimations in human plasma. It is simple, rapid, selective and capable of detecting and determining COX-2 inhibitors with a detection limit of 0.127--1.040 microg/mL simultaneously.     

Aminocatalytic Cross‐Coupling Approach via Iminium Ions to Different CC Bonds

Given the attractive ability of iminium ions to functionalize molecules directly at ostensibly unreactive positions, the reactivity of iminium ions, in which an α CH₂ group is replaced by C?O was explored. Background studies on the ability of such iminium cations to promote reactions via an iminium‐catalyzed or iminium‐equivalent pathway are apparently unavailable. Previously, tandem cross‐coupling reactions were reported, in which an iminium ion undergoes nucleophilic 1,2‐addition to give a putative three‐component intermediate that abstracts a proton in situ and undergoes self‐deamination followed by unprecedented DMSO/aerobic oxidation to generate α‐ketoamides. However, later it was observed that iminium ions can generate valuable α‐ketoamides through simple aerobic oxidation. In all reactions, iminium ions were generated in situ by reaction of 2‐oxoaldehydes with secondary amines.     

Cp*CoIII‐Catalyzed C(sp3)−H Bond Amidation of 8‐Methylquinoline

An efficient and external oxidant‐free, Cp*Co^III‐catalyzed C(sp³)?H bond amidation of 8‐methylquinoline, using oxazolone as an efficient amidating agent, is reported for the first time under mild conditions. The reaction is selective and tolerates a variety of functional groups. Based on previous reports and experimental results, the deprotonation pathway proceeds through an external base‐assisted concerted metalation and deprotonation process.     

Detection of Uric Acid in the Presence of Dopamine and High Concentration of Ascorbic Acid Using PDDA Modified Graphite Electrode

The properties of graphite electrode (Gr) modified with poly(diallyl dimethyl ammonium chloride) (PDDA) for the detection of uric acid (UA) in the presence of dopamine (DA) and high concentration of ascorbic acid (AA) have been investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The polymer modified graphite electrode was prepared by a very simple method just by immersing the graphite electrode in PDDA solution for 20 minutes. The PDDA/Gr modified electrode displayed excellent electrocatalytic activity towards the oxidation of UA, DA and AA compared to that at the bare graphite electrode. The electrochemical oxidation signals of UA, DA and AA are well resolved into three distinct peaks with peak potential separations of 220 mV, 168 mV and 387 mV between AA‐DA, DA‐UA and AA‐UA respectively in cyclic voltammetry studies and the corresponding peak potential separations are 230 mV, 130 mV and 354 mV respectively in differential pulse voltammetry. The lowest detection limits obtained for UA, DA and AA were 1×10^?7 M, 2×10^?7 M and 800×10^?9 M respectively. The PDDA/Gr electrode efficiently eliminated the interference of DA and a high concentration of AA in the determination of UA with good selectivity, sensitivity and reproducibility. The modified electrode was also successfully applied for simultaneous determination of UA, DA and AA in their ternary mixture.     

Photo Catalytic Degradation of Azo Dyes over Mn2+ Doped TiO2 Catalyst under UV/Solar Light:An Insight to the Route of Electron Transfer in the Mixed Phase of Anatase and Rutile

Mn²⁺ ion was doped into the TiO₂ matrix and its photocatalytic activity was evaluated for the degradation of a mono azo dye methyl orange (MO) and a di‐azo dye brilliant yellow (BY) under UV/solar light. X‐ray diffraction results revealed the phase transformation from anatase to rutile due to the inclusion of Mn²⁺ ion into the TiO₂ matrix. All the doped catalysts showed a red shift in the band gap to the visible region. The degradation reaction of the dyes was found to be dependent on its structure. It was found that mono azo dye degrades faster than di azo dye under UV/solar light. The rate constant under identical conditions calculated for the degradation of MO is 2.4 times (under UV light) and 4.5 times (under solar light) higher compared to BY. Among the photocatalysts studied, Mn²⁺(0.06 at.%)‐TiO₂ showed higher activity under both UV and solar light illumination. The synergestic effect in the bicrystalline framework of anatase and rutile effectively suppresses the charge carrier recombination and enhances the photocatalytic activity. The degradation reaction was followed by UV‐visible spectroscopy and the photoproducts formed were analyzed by GC‐MS techniques.     

Vanadium pentoxide nanobelts: One pot synthesis and its lithium storage behavior

In this paper, we report a synthesis, characterization and electrochemical properties of V₂O₅ nanobelts. V₂O₅ nanobelts have been prepared via hydrothermal treatment of commercial V₂O₅ in acidic (HCl/H₂SO₄) medium at relatively low temperature (160 °C). The hydrothermally derived products have been characterized by powder X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), Raman spectroscopy, X‐ray photo electron spectroscopy (XPS), UV‐Vis spectroscopy, Scanning/Transmission electron microscopy (SEM/TEM). XRD pattern of V₂O₅ nanobelts show an orthorhombic phase. From the FTIR spectrum, the peak observed at 1018 cm⁻¹ is characteristic of the stretching vibration mode of the terminal vanadyl, V = O. The UV‐Vis absorption spectrum of V₂O₅ nanobelts show maximum absorbance at 430 nm, which was blue‐shifted compared to that of bulk V₂O₅. TEM micrographs reveal that the products consist of nanobelts of 40‐200 nm in thickness and several tens of micrometers in length. The electrochemical analysis shows an initial discharge capacity of 360 mAh g⁻¹ and its almost stabilized capacity is reached to 250 mAh g⁻¹ after 55 cycles. A probable reaction mechanism for the formation of orthorhombic V₂O₅ nanobelts is proposed.