A novel multi-component reaction of indole, formaldehyde, and tertiary aromatic amines

A novel multi-component reaction of indoles, formaldehydes, and tertiary aromatic amines is described for the synthesis of dialkylaminoarylated indoles using silica-supported perchloric acid (HClO₄-SiO₂) as an inexpensive and highly efficient catalyst. The key features of this multi-component reactions are operational simplicity, mild reaction conditions, regioselectivity, and recycling of catalyst.     

pH‐Zone‐refining centrifugal partition chromatography for preparative isolation and purification of steroidal glycoalkaloids from Solanum xanthocarpum

pH‐Zone‐refining centrifugal‐partition chromatography (CPC) was successfully applied in the separation of complex polar steroidal glycoalkaloids of close Rf values, directly from a crude extract of Solanum xanthocarpum. The experiment was performed with a two phase solvent system composed of ethyl acetate/butanol/water (1:4:5 by volume) where triethylamine (5 mM) was added to the upper organic mobile phase as an eluter and TFA (10 mM) to the aqueous stationary phase as a retainer. Separation of 1 g of crude extract over CPC resulted in two distinct pH‐zones. The fractions collected in pH‐zone i afforded 72 mg of solasonine while the fractions collected in pH‐zone ii were slightly impure, hence were purified over medium pressure LC, which afforded 30 mg of solasonine and further 15 mg of solamargine (SM). The steroidal glycoalkaloids, SM and solasonine were isolated in 93.3 and 91.6% purity, respectively. The isolated alkaloids were characterized on the basis of their ¹H, ¹³C‐NMR, and ESI‐MS data.     

Capacitively coupled contactless conductivity detection with dual top–bottom cell configuration for microchip electrophoresis

An optimized capacitively coupled contactless conductivity detector for microchip electophoresis is presented. The detector consists of a pair of top–bottom excitation electrodes and a pair of pickup electrodes disposed onto a very thin plastic microfluidic chip. The detection cell formed by the electrodes is completely encased and shielded in a metal housing. These approaches allow for the enhancement of signal coupling and extraction from the detection cell that result in an improved signal‐to‐noise‐ratio and detection sensitivity. The improved detector performance is illustrated by the electrophoretic separation of six cations (NH, K⁺, Ca²⁺, Na⁺, Mg²⁺, Li⁺) with a detection limit of approximately 0.3 μM and the analysis of the anions (Br^?, Cl^?, NO, NO, SO, F^?) with a detection limit of about 0.15 μM. These LODs are significantly improved compared with previous reports using the conventional top–top electrode geometry. The developed system was applied to the analysis of ions in bottled drinking water samples.     

Development of a validated LC method for enantiomeric separation and determination of adrafinil and its related substances on a Chiralcel OJ-H column connected to PDA and polarimetric detectors in series

A rapid and reliable high‐performance liquid chromatographic method for resolution of enantiomers of adrafinil [(±)‐ADL], a novel vigilance promoting agent, and its synthetic intermediates was developed. The separation was carried out on a Chiralcel OJ‐H using n‐hexane–ethanol (62:38 v/v) as a mobile phase. The detection was carried out at 225 nm using a photodiode array (PDA) detector. The optical rotation and order of elution of enantiomers were assigned. The method is suitable not only for process development of ADL but also for quality assurance of bulk drugs and pharmaceuticals. Copyright © 2010 John Wiley & Sons, Ltd.     

Nanostructured lead-free ferroelectric Na0.5Bi0.5TiO3-BaTiO3 whiskers: synthesis mechanism and structure

Nanostructured lead-free ferroelectric Na(0.5)Bi(0.5)TiO(3)-BaTiO(3) (NBTBT) whiskers with a high aspect ratio were synthesized topochemically using Na(2)Ti(6)O(13) (NTO) as a host structure for the first time. High energy X-ray diffraction coupled with an atomic pair distribution function (PDF) and Raman scattering analyses were used to confirm the average structure of the lead-free NBTBT whiskers, which was found to be rhombohedral, i.e. a ferroelectric enabling type. High resolution transmission electron microscopic (HRTEM) analysis revealed local monoclinic-type structural distortions, indicating a modulated structure at the nanoscale in the morphotropic phase boundary (MPB) composition of the lead-free NBTBT whiskers. The structural rearrangement during the synthesis of the lead-free NBTBT whiskers was found to occur via translation of the edge shared octahedra of NTO into a corner sharing coordination. High temperature morphological changes that depict the disintegration of the isolated whiskers into their individual grains due to the higher grain boundary energy have been found to occur in close analogy with Rayleigh-type instability.     

Study of photoconductive and dielectric dependence of gain and phase-shift in the coupled unidirectional ring resonators based on non-degenerate wave-mixing in photorefractive materials

Photoconductive and dielectric dependence of gain and phase-shift in the coupled unidirectional photorefractive ring resonators (UPRR) have been analyzed for the case of non-degenerate two-wave mixing in photorefractive materials by employing the plane-wave approximation method. The effect of photoconductivity and dielectric constant of the coupled photorefractive crystals (A and B) on the gain and phase-shift in the coupled UPRR have also been studied in details. It has been found that for a given value of the photoconductivity of crystal B, the gain in the primary resonator can be enhanced by selecting lower value of frequency detuning of the same resonator and PR crystal A of higher photoconductivity in the coupled UPRR. But reverse of the case is found for the enhancement of phase-shift. Such enhancement of the gain and phase-shift in the primary resonator are responsible for build-up and non-reciprocal energy transfer between the modes of the internal oscillations, which greatly improves the performance of the coupled UPRR.     

Well Behaved Charged Generalization of Buchdahl’s Fluid Spheres

In the present article, we have obtained a class of well behaved charged analogues of Buchdahl (Phys. Rev. 116:1027–1034, 1959) neutral perfect fluid solution, which reduces to its neutral counter part in the absence of charge. The solutions so obtained are utilized to depict the super-dense stars models such as models for neutron stars and strange star. It is observed that the models are well behaved for restricted range of the parameter K (1<K≤1.64). Over all the maximum mass and corresponding radius is 2.4495M _Θ and 16.7289 respectively and moment of inertia . Also the pulsars character of the super-dense stars so obtained and has been analyzed with the help of moment of inertia. The analysis of the models reveals both vela and crab pulsars.     

Dioxo- and oxovanadium(V) complexes of thiohydrazone ONS donor ligands: synthesis, characterization, reactivity, and antiamoebic activity

As a contribution to the development of novel vanadium complexes with pharmacologically interesting properties, two neutral dioxovanadium(V) complexes [VO2(Hpydx-sbdt)] (1) and [VO2(Hpydx-smdt)] (3) [H2pydx-sbdt (I) and H2pydx-smdt (II) are the Schiff bases derived from pyridoxal and S-benzyl- or S-methyldithiocarbazate] have been synthesized by the reaction of [VO(acac)2] and the potassium salts of the ligands in methanol followed by aerial oxidation. Heating of the methanolic solutions of these complexes yields the oxo-bridged binuclear complexes [{VO(pydx-sbdt)}2mu-O] (2) and [{VO(pydx-smdt)}2mu-O] (4). The crystals and molecular structures of 1, 3 x 1.5H2O, and 4 x 2CH3OH have been determined, confirming the ONS binding mode of the dianionic ligands in their thioenolate form. The ring nitrogen of the pyridoxal moiety is protonated in complexes 1 and 3. Acidification of 1 and 3 with HCl dissolved in methanol afforded oxohydroxo complexes, while in a methanolic KOH solution, the corresponding dioxo species K[VO2(pydx-sbdt/smdt)] are formed. Treatment of 1 and 3 with H2O2 yields (unstable) oxoperoxovanadium(V) complexes, the formation of which has been established spectrophotometrically. In vitro antiamoebic activities (against HM1:1MSS strain of Entamoeba histolytica) were established for all of the dioxo- and oxovanadium(V) complexes. The complexes 1, 2, and 4 were more effective than metronidazole, a commonly used drug against amoebiasis, suggesting that oxovanadium(V) complexes derived from thiohydrazones may open a new dimension in the therapy of amoebiasis.     

Quantification of tizanidine in human plasma by liquid chromatography coupled to tandem mass spectrometry

A simple, sensitive and rapid high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry (MS/MS) method was developed and validated for the assay of tizanidine in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase column and analyzed by MS/MS in the selected reaction monitoring mode. The assay exhibited a linear dynamic range of 50-5000 pg/mL for tizanidine in human plasma. The lower limit of quantification was 50 pg/mL with a relative standard deviation of less than 13%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.5 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.     

Diversity-oriented synthesis of benzimidazole,benzoxazole, benzothiazole and quinazolin-4(3H)-one libraries via potassium persulfate–CuSO<Subscript>4</Subscript>-mediated oxidative coupling reactions of aldehydes in aqueous micelles

Libraries of 2-substituted-benzimidazoles, benzoxazoles, benzothiazoles as well as quinazolin-4(3H)-ones were synthesized via potassium persulfate–CuSO₄-mediated oxidative coupling of aldehydes with o-phenylenediamines, o-aminophenols, o-aminothiophenols, and anthranilamide, respectively, in aqueous micelles. The strategy opens a way for rapid generation of libraries of small heterocycles for biological screening. The reagent is commercially available, cheap, and highly chemoselective. The yields were superior in aqueous micelles to those in organic solvents. Short reaction times, large-scale synthesis, excellent chemoselectivity, excellent yields, as well as environmental friendliness are the main advantages of this diversity-oriented synthesis.