Palladium(0)-Mediated Synthesis of Acetylated Unsaturated 1,4-Disaccharides

Abstract

Alkylation of ethyl 6-O-tert-butyldiphenylsilyl-4-O-methoxycarbonyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranoside (1) with various peracetylated 1-hydroxy sugars in the presence of a catalytic amount of palladium(O) gave the corresponding unsaturated 1,4-disaccharides and trisaccharides. In all cases the reaction is regio- and stereospecific according to the unsaturated moiety, alkylation occuring only at C-4 of the unsaturated carbohydrate, with overall retention of configuration.     

Pharmacokinetic study of amoxicillin in human plasma by solid‐phase microextraction followed by high‐performance liquid chromatography–triple quadrupole mass spectrometry

Sensitive and selective analytical procedures based on high‐performance liquid chromatography with mass spectrometric detection were developed for the determination of amoxicillin in human plasma samples. Samples were prepared by applying in‐house manufactured molecularly imprinted solid‐phase microextraction probes. The detection of target compounds was performed in multiple reaction monitoring mode. The multiple reaction monitoring detection was operated in the positive electrospray ionization mode using the transitions of m/z 366 ([M + H]⁺) → 349 for amoxicillin and m/z 390 ([M + H]⁺) → 372 for gemifloxacin. The method was validated with precision within 15% relative standard deviation and accuracy within 15% relative error. The method was successfully applied to study of the pharmacokinetics of amoxicillin in human plasma after oral administration of amoxicillin. Copyright © 2013 John Wiley & Sons, Ltd.     

Influence of temperature on mass transfer in an incomplete trapping supported liquid membrane extraction of triazole fungicides

The influence of temperature in a supported liquid membrane (SLM) extraction of triazole fungicides was investigated. The mass transfer parameters such as diffusion coefficient, flux and apparent viscosity were determined at temperatures ranging from 5 to 40°C. Increase in temperature led to an increase in diffusion coefficient and flux with a flowing acceptor solution. The apparent viscosity also decreased with an increase in temperature. However, the increase in mass transfer parameters did not result in an overall increase in extraction efficiency with a stagnant or circulation acceptor phase. Stripping of the analytes from the membrane into the acceptor phase as well as the configuration of the extraction unit could have limited the influence of temperature on mass transfer. The partition coefficient of analytes from the acceptor solution to the membrane, K_A, was found to be much higher than that from the donor solution to the membrane K_D, thus triazole compounds preferred to remain in the membrane even with an increased extraction temperature.     

The effect of stationary phase on lipophilicity determination of beta-blockers using reverse-phase chromatographic systems

Evaluation of lipophilicity parameters for basic compounds using different chromatographic stationary phases is presented. An HPLC method for determination of lipophilic molecule-stationary phase interactions was based on gradient analysis. Differences in correlation between the lipophilicity of compounds and experimental chromatographic results obtained in pseudo-membrane systems showed a strong influence of stationary phase structure and physico-chemical properties. beta-Blocker drugs with varying lipophilicity and bio-activity were chosen as test compounds. The stationary phases used for the study were monolithic rod-structure C18 and silica gel octadecyl phase SG-C18 as reference material. The second group was silica gel-based polar-embedded alkylamide and cholesterolic phases. The mobile phase was composed of acetonitrile or methanol with ammonium acetate, and a linear gradient of methanol and acetonitrile in mobile phase was performed. A linear correlation of plots of log k(g) = f(log P) was observed, especially for polar-embedded phases, and this allowed log P(HPLC) to be calculated. The behavior of stationary phases in methanol and acetonitrile buffer showed differences between obtained log P(HPLC) values.     

On log-Sobolev inequalities for infinite lattice systems

For a system on an infinite lattice, we show that a Gibbs measure for a smooth local specification ={E } satisfying the Dobrushin uniqueness theorem also satisfies log-Sobolev inequality, provided it is satisfied for one-dimensional measures E _l .     

Tissue sample preparations for preclinical research determined by molecular imaging mass spectrometry using matrix-assisted laser desorption/ionization

Matrix-assisted laser desorption/ionization - imaging mass spectrometry is an alternative tool, which can be implemented in order to obtain and visualize the “omic” signature of tissue samples. Its application to clinical study enables simultaneous imaging-based morphological observations and mass spectrometry analysis. Application of fully informative material like tissue allows obtaining the complex and unique profile of analyzed samples. This knowledge leads to diagnosing disease, studying the mechanism of cancer development, selecting the potential biomarkers as well as correlating obtained images with prognosis. Nevertheless, it is worth noticing that this method is found to be objective but the result of the analysis is mainly influenced by the sample preparation protocol, including the collection of biological material, its preservation, and processing. However, the application of this approach requires a special sample preparation procedure. The main goal of the study is to present the current knowledge on the clinical application of matrix-assisted laser desorption/ionization with imaging mass spectrometry in cancer research, with particular emphasis on the sample preparation step. For this purpose, several protocols based on cryosections and formalin-fixed paraffin-embedded tissue were compiled and compared, taking into account the measured metabolites of potential diagnostic importance for a given type of cancer.     

A.c. impedance behaviour of processes involving adsorption and reactivity of guanidonium-type cations at Pt(1 0 0) surface

The present paper reports a.c. impedance spectroscopic studies on adsorption of guanidonium (G⁺) and N,N-dimethylguanidonium (DMG⁺) resonant cations at Pt(1 0 0) single-crystal surface. The resulted information provided confirmation of the role of electrosorption of the above-mentioned molecule–ions through evaluation of the associated charge-transfer resistances and capacitances for the Pt(1 0 0) plane in 0.5 M H₂SO₄. These results also provided support for the interfacial ion-pairing mechanism that had been based on the voltammetric and in situ FTIR spectroscopic results published earlier.     

Two-color particle image velocimetry technique for an internal combustion engine

A two-color particle image velocimetry (PIV) technique has been applied to a single-cylinder motored research engine. Two-color PIV is a quantitative planar velocity measurement technique that can unambiguously determine the velocity magnitude and direction.

The work includes the development of an interrogation system, a series of computer simulations to determine the performance of the technique under various conditions, the comparison of these results to similar ones obtained for an autocorrelation PIV system, and a test of the technique by reconstructing the velocity field of a uniform jet flow.

The technique was then applied to the in-cylinder flow field of a motored single-cylinder, cup-in-head, research engine. A total of 27 instantaneous velocity fields were obtained at a single measurement plane for a single operating condition of the engine. The data were analyzed to yield ensemble-averaged velocity and velocity fluctuation.