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.     

Three new ingol diterpenes from Euphorbia nivulia: evaluation of cytotoxic activity

The latex of Euphorbia nivulia afforded three new ingol diterpenes, 3-acetyl-8-methoxyl-7-angolyl-12-hydroxylingol (7), 3,12-diacetyl-7-hydroxy-8-methoxylingol (8), and 3,12-diacetyl-7-angolyl-8-hydroxylingol (9) along with five known ingol diterpenes 2-6 and a known triterpene cyclonivulinol (1). Their structures were established by means of spectroscopic analysis. Diterpenes 2-9 were evaluated for their cytotoxic activity.     

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.     

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.     

A rapid method for the separation of radium from Tuwa spring waters for determining the activity ratio of223Ra/226Ra

A rapid method for the separation of radium in spring waters of Tuwa, Panchamahal district, Gujarat State, India, containing large amounts of calcium (0.5 g/l) has been developed. It consists of concentrating polyvalent cations from 21 samples using 10 g of carboxylate exchanger, Zeokarb 226 (NH ₄ ⁺ ) and then precipitating radium as sulfate in the presence of 400 μg of barium.     

Classification and identification of mosquito species using artificial neural networks

An artificial neural network method is presented for classification and identification of Anopheles mosquito species based on the internal transcribed spacer2 (ITS2) data of ribosomal DNA string. The method is implemented in two different multi-layered feed-forward neural network model forms, namely, multi-input single-output neural network (MISONN) and multi-input multi-output neural network (MIMONN). A number of data sequences in varying sizes of different Anopheline malarial vectors and their corresponding species coding are employed to develop the neural network models. The classification efficiency of the network models for untrained data sequences is evaluated in terms of quantitative performance criteria. The results demonstrate the efficiency of the neural network models to extract the genetic information in ITS2 sequences and to adapt to new data. The method of MISONN is found to exhibit superior performance over MIMONN in distinguishing and identification of the mosquito vectors.     

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.     

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     

Simultaneous Determination of Ritonavir and Lopinavir in Human Plasma after Protein Precipitation and LC-MS-MS

A simple, rapid, specific and sensitive method has been developed and validated for simultaneous determination of lopinavir and ritonavir in human plasma. The analytical procedure involves a protein precipitation method using fluoxetine as internal standard Separation was carried out on an Inertsil ODS column using a mobile phase consisting of acetonitrile and 5 mM ammonium acetate buffer. The total run time of analysis was 2.0 min. A linear response function was established for the range of concentrations 50.67–10,008.82 ng mL^?1 for lopinavir and 5.066–1,000.693 ng mL^?1 for ritonavir. The method was successfully applied to an oral bioequivalence study in humans.