But-2-ynylbisoxycarbonyl chloride: a novel C2-symmetric reagent for the protection of amines and amino acids

[reaction: see text] A novel C2-symmetric protecting group for amines, the but-2-ynylbisoxycarbonyl (Bbc) group, is developed, which can be deblocked with tetrathiomolybdate under neutral conditions. One equivalent of the bischloroformate, BbcCl, is used for the protection of 2 equiv of the amine. Its application in peptide synthesis is established through the synthesis of a tripeptide, and its orthogonality with Cbz, Fmoc, and Boc groups has been studied.     

Electric field effect in diluted magnetic insulator anatase Co: TiO2

An external electric field induced reversible modulation of a room temperature magnetic moment and coercive field is achieved in an epitaxial and insulating thin film of dilutely cobalt-doped anatase TiO2. This first demonstration of an electric field effect in any oxide-based diluted ferromagnet is realized in a high quality epitaxial heterostructure of PbZr(0.2)Ti(0.8)O(3)/Co: TiO(2)/SrRuO(3) grown on (001) LaAlO3. The observed effect, which is about 15% in strength in a given heterostructure, can be modulated over several cycles. Possible mechanisms for electric field induced modulation of insulating ferromagnetism are discussed.     

Forced responses of solid axially polarized piezoelectric ceramic finite cylinders with internal losses

A method is presented to determine the forced responses of piezoelectric cylinders using weighted sums of only certain exact solutions to the equations of motion and the Gauss electrostatic conditions. One infinite set of solutions is chosen such that each field variable is expressed in terms of Bessel functions that form a complete set in the radial direction. Another infinite set of solutions is chosen such that each field variable is expressed in terms of trigonometric functions that form a complete set in the axial direction. Another solution is used to account for the electric field that can exist even when there is no vibration. The weights are determined by using the orthogonal properties of the functions and are used to satisfy specified, arbitrary, axisymmetric boundary conditions on all the surfaces. Special cases including simultaneous mechanical and electrical excitation of cylinders are presented. All numerical results are in excellent agreement with those obtained using the finite element software ATILA. For example, the five lowest frequencies at which the conductance and susceptance of a stress-free cylinder, of length 10 mm and radius 5 mm, reach a local maximum or minimum differ by less than 0.01% from those computed using ATILA.     

Coherent backscattering spectroscopy

Coherent backscattering (CBS) of light in random media has been previously investigated by use of coherent light sources. Here we report a novel method of CBS measurement that combines low spatial coherence, broadband illumination, and spectrally resolved detection. We show that low spatial coherence illumination leads to an anomalously broad CBS peak and a dramatic speckle reduction; the latter is further facilitated by low temporal coherence detection. Thus CBS can be observed in biological tissue and other media that previously were beyond the reach of conventional CBS measurements. We also demonstrate, for the first time to our knowledge, spectroscopic analysis of CBS. CBS spectroscopy may find important applications in probing random media such as biological tissue in which depth-selective measurements are crucial.     

Simple,efficient, and selective deprotection of phenolic methoxymethyl ethers using silica-supported sodium hydrogen sulfate as a heterogeneous catalyst

A simple and efficient method has been developed for chemoselective deprotection of phenolic methoxymethyl (MOM) ethers using silica-supported sodium hydrogen sulfate as a heterogeneous catalyst. The conversions occur at room temperature, and the yields of the deprotected phenols are excellent. The method is suitable for deprotection of phenolic MOM ethers of multifunctional bioactive natural products.     

Measurement of internal stresses via the polarization in epitaxial ferroelectric films

The relations between electrical and mechanical properties of constrained ferroelectric films are analyzed. It is shown that the internal stresses and the elastic constants can be determined through the measurement of the electrical response. The change in the polarization is proportional to internal stresses due to film-substrate misfit, whereas the linear electrical and electromechanical responses to external field do not depend on the misfit and are determined by the film constraint. The theoretical results are successfully applied to PbZr 0.2Ti 0.8O (3) films on (001) LaAlO (3) substrate which exhibit a considerable increase in the saturation polarization due to epitaxial stresses. Significant recovery in the piezoelectric constant and susceptibility is theoretically predicted and experimentally verified for specific film configurations which reduce the degree of constraint. The concept presented in this Letter can be expanded to constrained ferromagnetic and superconductor films.     

Development and validation of a HPLC method for quantification of rivastigmine in rat urine and identification of a novel metabolite in urine by LC‐MS/MS

A sensitive, specific and accurate HPLC method for the quantification of rivastigmine (RSM) in rat urine was developed and validated. The method involves the simple liquid–liquid extraction of RSM and pyridostigmine as an internal standard (IS) from rat urine with tertiary methyl butyl ether. The chromatographic separation of RSM and IS was achieved with 20 mm ammonium acetate buffer (pH 6.5) and acetonitrile (65:35, v/v) delivered at flow‐rate of 1 mL/min on a Kromasil KR‐100. The method was in linear range from 50 to 5000 ng/mL. The validation was done as per FDA guidelines and the results met the acceptance criteria. The method was successfully applied for the quantification of RSM in rat urine. Besides method validation, we have identified two metabolites of RSM in urine. Both the metabolites were characterized by HPLC‐PDA and LC‐MS/MS and it was found that one metabolite is novel. Copyright © 2010 John Wiley & Sons, Ltd.     

Simultaneous estimation of four proton pump inhibitors—lansoprazole,omeprazole, pantoprazole and rabeprazole: development of a novel generic HPLC‐UV method and its application to clinical pharmacokinetic study

A highly selective, sensitive and accurate HPLC method has been developed and validated for the estimation of four proton‐pump inhibitors (PPI), lansoprazole (LPZ), omeprazole (OPZ), pantoprazole (PPZ) and rabeprazole (RPZ), with 500 µL human plasma using zonisamide as an internal standard (IS). The sample preparation involved simple liquid–liquid extraction of LPZ, OPZ, PPZ and RPZ and IS from human plasma with ethyl acetate. The baseline separation of all the peaks was achieved with 0.1% triethylamine (pH 6.0):acetonitrile (72:28, v/v) at a flow rate of 1 mL/min on a Zorbax C₈ column. The total chromatographic run time was 11.0 min and the simultaneous elution of IS, OPZ, RPZ, PPZ and LPZ occurred at approximately 2.42, 4.45, 5.02 and 9.37 min, respectively. The method was proved to be accurate and precise at linearity range of 20.61–1999.79 ng/mL with a correlation coefficient (r) of ≥0.999. The limit of quantitation for each of the PPI studied was 20.61 ng/mL. The intra‐ and inter‐day precision and accuracy values were found to be within the assay variability limits as per the FDA guidelines. The developed assay method was applied to a pharmacokinetic study in human volunteers. Copyright © 2009 John Wiley & Sons, Ltd.     

Development and validation of a highly sensitive LC‐MS/MS‐ESI method for the determination of bicalutamide in mouse plasma: application to a pharmacokinetic study

A highly sensitive, rapid assay method has been developed and validated for the estimation of bicalutamide in mouse plasma using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the negative‐ion mode. The assay procedure involves extraction of bicalutamide and tolbutamide (internal standard, IS) from mouse plasma with a simple protein precipitation method. Chromatographic separation was achieved using an isocratic mobile phase (0.2% formic acid:acetonitrile, 35:65, v/v) at a flow rate of 0.5 mL/min on an Atlantis dC₁₈ column (maintained at 40 ± 1°C) with a total run time of 3.0 min. The MS/MS ion transitions monitored were m/z 428.9 → 254.7 for bicalutamide and m/z 269.0 → 169.6 for IS. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 1.04 ng/mL and the linearity range extended from 1.04 to 1877 ng/mL. The intra‐ and inter‐day precisions were in the ranges of 0.49–4.68 and 2.62–4.15, respectively. Copyright © 2012 John Wiley & Sons, Ltd.