Isolation and synthesis of a novel β-carboline guanidine derivative tiruchanduramine from the Indian ascidian Synoicum macroglossum

The isolation and synthesis of the racemic form of a novel β-carboline guanidine alkaloid, tiruchanduramine, a potent α-glucosidase inhibitor from the Indian ascidian, Synoicum macroglossum has been achieved.     

Development of kinetic models for acid‐catalyzed methyl acetate formation reaction: Effect of catalyst concentration and water inhibition

The reaction kinetics of reversible liquid‐phase esterification of acetic acid with methanol is investigated in the temperature range 26–50°C using sulfuric acid catalyst. The main goal of this work is to study the effect of catalyst concentration and sensitivity to the presence of water on the rate expression of this industrially important reaction. Experiments are conducted in an isothermal batch reactor and a second‐order kinetic model is used to correlate the experimental data, which are found to fit well with the assumed kinetic model in terms of the concentrations of reactants and products. Furthermore, an activity‐based kinetic model is also developed employing the UNIQUAC (universal quasi‐chemical equation) model to compute the activities. It is observed that the rate constant is influenced by the concentration of catalyst, and the reaction rate increased with an increase in the catalyst concentration. It is also observed that the catalyst activity is slightly inhibited by the water present in the reaction mixture. The performance of the proposed models is compared with that of other models reported in the literature, and it is found that the proposed models outperformed all the other models reported in the literature. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 263–277, 2011     

Emission spectrum of bismuth monochloride

Bismuth chloride has been excited in flowing condition with an uncondensed transformer discharge. About 390 bands are observed in the present experiments of which only 140 were recorded by earlier workers. The vibrational constants obtained are the same as those obtained by Morgan from obsorption experiments except for the addition of a cubic term for the upper state. It appears quite likely that the upper state of the system dissociates into Bi (⁴S_3/2) + Cl (²P_1/2) while the lower state, which is probably the ground state, dissociates into Bi (⁴S_3/2) + Cl (²P_3/2). The rough values of the dissociation energies obtained by extrapolations are D₀′=3750 cm.^?1 and D₀″=24614 cm.^?1     

DDQ-mediated direct oxidative coupling of amides with benzylic and allylic sp3 C–H bonds under metal-free conditions

A simple and efficient method for the direct oxidative coupling of amides with benzylic and allylic sp³ C–H bonds using DDQ as an oxidant is described. A range of amides including benzamide, benzyl carbamate, and substituted sulfonamides reacted efficiently with various benzylic and allylic substrates under metal free conditions to afford amidation products in good to excellent yields.     

Liquid chromatography–tandem mass spectrometric assay for the determination of tetrabenazine and its active metabolites in human plasma: a pharmacokinetic study

A simple, rapid and sensitive liquid chromatography–tandem mass spectrometric (LC‐MS/MS) assay method has been developed and fully validated for the simultaneous quantification of tetrabenazine and its active metabolites α‐dihydrotetrabenazine and β‐dihydrotetrabenazine in human plasma. Tetrabenazine d7 was used as internal standard (IS). The analytes were extracted from 200 μL aliquots of human plasma via solid‐phase extraction using C₁₈ solid‐phase extraction cartridges. The reconstituted samples were chromatographed on a Zorbax SB C₁₈ column using a 60:40 (v/v) mixture of acetonitrile and 5 mm ammonium acetate as the mobile phase at a flow rate of 0.8 mL/min. The API‐4000 LC‐MS/MS in multiple reaction‐monitoring mode was used for detection. The calibration curves obtained were linear (r² ≥ 0.99) over the concentration range of 0.01–5.03 ng/mL for tetrabenazine and 0.50–100 ng/mL for α‐dihydrotetrabenazine and β‐dihydrotetrabenazine. Method validation was performed as per Food and Drug Administration guidelines and the results met the acceptance criteria. The method is precise and sensitive enough for its intended purpose. A run time of 2.5 min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was found to be applicable to clinical studies. Copyright © 2013 John Wiley & Sons, Ltd.     

Enhanced electrochemical performance of carbon-coated LiMPO<Subscript>4</Subscript> (M = Co and Ni) nanoparticles as cathodes for high-voltage lithium-ion battery

Olivine LiMPO₄ (M = Co and Ni) nanoparticles have been synthesized by the polyvinylpyrrolidone (PVP) assisted polyol method and adopted the resin coating process for carbon coating on the surface of the nanoparticles. The X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies confirmed the phase and structural co-ordination of bare and carbon-coated LiMPO₄ (M = Co and Ni) nanoparticles, respectively. The formation of uniform carbon layer of nanometer-measured thickness over nanoparticles is confirmed by the high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDS). Wagner’s polarization study explains an improved electronic transport number (t _e) for carbon-coated LiMPO₄ (M = Co and Ni) cathodes as compared to bare samples. The electrochemical study of the Li-ion cells shows the first cycle discharge capacities of 180 and 97 mAh/g at 0.1 C for the cathodes LiCoPO₄/C and LiNiPO₄/C, respectively, which is an improvement of 21.2 and 25.8 % as compared to bare samples. The enhancement of electrochemical performance of the cells is attributed to the improved electronic properties of cathode materials due to the presence of carbon on the surface of nanoparticles.     

A highly efficient stereoselective synthesis of (Z)- and (E)-allyl iodides from Baylis-Hillman adducts

A highly efficient synthesis of (Z)- and (E)-allyl iodides has been accomplished by treatment of Baylis-Hillman adducts with iodine and triphenylphosphine in methylene chloride at room temperature. The method is associated with mild reaction conditions, high yields and excellent stereoselectivity.     

Total Synthesis of (−)‐Cleistenolide

An efficient and short total synthesis of (?)‐cleistenolide ( 1 ) from D ‐mannitol with an overall yield of 23.6% is described. The chiron approach for the synthesis of (?)‐cleistenolide involves a one‐C‐atom Wittig olefination, a selective allylic triethylsilyl protection, and a Grubbs‐catalyzed ring‐closure‐metathesis (RCM) reaction as the key steps.     

Polarographic determination of iron(II) and iron(III) complexes with edta

The iron(II) and iron(III) complexes with EDTA can be determined separately and in mixtures in acetate-buffered medium at pH 4.0. The E_{$\text{1}\text{2}$}values are in the range ?0.105 to ?0.112 V vs. SCE. Linear calibration plots are obtained over the range 0–1.0 mM for each oxidation state. A sample-handling procedure for avoiding oxidation of iron(II) species is described. It is shown that the acetate buffer system does not affect the stability of the iron-EDTA complexes.     

Transformations of lignans. Part 10: Acid-catalysed rearrangements of arboreol and wodeshiol and conversion of gmelanone oxime into a dihydropyranone derivative

The synthesis of gmelanone 2 by a pinacol-type rearrangement of arboreol 1 supports its biogenesis and confirms its relative and absolute configuration. The further transformation of gmelanone oxime 12 into the dihydropyranone oxime 13 supports the intermediacy of gmelanone like intermediates in the rearrangements of furofuran lignans to pyran derivatives. In contrast, acid-catalysed rearrangement of wodeshiol 7 affords the dihydropyranone 8.