Monothiolate ruthenium alkylidene complexes with tricyclic fluorinated N-heterocyclic carbene ligands

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A Bulky Chiral N‐Heterocyclic Carbene Nickel Catalyst Enables Enantioselective C−H Functionalizations of Indoles and Pyrroles

An enantioselective nickel(0)‐catalyzed C?H functionalization of indoles and pyrroles that does not require the typical Lewis basic directing groups is disclosed. The reaction provides access to valuable tetrahydropyridoindoles and tetrahydroindolizines in high yields and enantioselectivity under mild reaction conditions. The process is characterized by a clear endo‐cyclization preference to yield the sought‐after six‐membered‐ring products. Key for the success of the activation and selectivity in the cyclization was the development of a novel chiral SIPr carbene ligand analogue with very bulky flanking groups.     

Quantitative determination of metformin,glyburide and its metabolites in plasma and urine of pregnant patients by LC‐MS/MS

This report describes the development and validation of an LC‐MS/MS method for the quantitative determination of glyburide (GLB), its five metabolites (M1, M2a, M2b, M3 and M4) and metformin (MET) in plasma and urine of pregnant patients under treatment with a combination of the two medications. The extraction recovery of the analytes from plasma samples was 87–99%, and that from urine samples was 85–95%. The differences in retention times among the analytes and the wide range of the concentrations of the medications and their metabolites in plasma and urine patient samples required the development of three LC methods. The lower limit of quantitation (LLOQ) of the analytes in plasma samples was as follows: GLB, 1.02 ng/mL; its five metabolites, 0.100–0.113 ng/mL; and MET, 4.95 ng/mL. The LLOQ in urine samples was 0.0594 ng/mL for GLB, 0.984–1.02 ng/mL for its five metabolites and 30.0 µg/mL for MET. The relative deviation of this method was <14% for intra‐day and inter‐day assays in plasma and urine samples, and the accuracy was 86–114% in plasma, and 94–105% in urine. The method described in this report was successfully utilized for determining the concentrations of the two medications in patient plasma and urine. Copyright © 2014 John Wiley & Sons, Ltd.     

Inverse electron-demand Diels-Alder (iEDDA) bioorthogonal conjugation of half-sandwich transition metallocarbonyl entities to a model protein

Novel transition metallocarbonyl complexes carrying a norbornene or an oxanorbornene group were synthesized by [4 + 2] cycloaddition between the organometallic maleimide dienophiles and cyclopentadiene or furan, respectively. The oxanorbornene adduct was obtained as a mixture of endo and exo isomers as confirmed by X-ray diffraction and NMR spectroscopy. The (oxa)norbornene groups further provided convenient chemical reporters to carry out inverse electron demand Diels-Alder (iEDDA) reactions with tetrazine derivatives. Detailed kinetic studies with a model tetrazine revealed that faster rates of reaction were determined with both isomers of the oxanorbornene complex with respect to the norbornene complexes. Eventually, incorporation of metallocarbonyl entities into bovine serum albumin equipped with tetrazine handles was achieved as shown by IR spectroscopy of the protein conjugates.     

A facile and sensitive HPLC–MS/MS method for quantification of 3,3′-diindolylmethane in plasma samples

Indole-3-carbinol is the subject of ongoing biomedical research owing to its potential antiatherogenic, anticarcinogenic and antioxidant effects. The antitumor properties are mainly associated with its major metabolite, i.e. 3,3′-diindolylmethane (DIM). Typically, the biological activity of the chemical compound is manifested in the ng/ml concentration range. Consequently, the development of highly sensitive analytical methods to determine DIM in various biological samples is an urgent issue. In this study, an HPLC–MS/MS method was established for the quantification of DIM in human plasma. The developed method was validated according to the European Medicines Agency guidelines. Sensitivity, selectivity, accuracy and precision were good, allowing DIM quantification in the concentration range of 5–500 ng/ml. The limit of detection and the lower limit of quantification were 1 and 5 ng/ml, respectively. 4-Methoxy-1-methylindole was used as an internal standard (IS). The analytes were extracted from the human plasma by the acetonitrile-induced protein precipitation method with the addition of 3 mol/L ammonium sulfate as a salting-out agent, which is a facile and efficient approach for high-throughput bioanalysis. The chromatographic separation was performed on the Synergi Fusion-RP C₁₈ column (50 × 2.0 mm, 4 μm, 80 Å) under isocratic elution at 40°C. The mobile phase consisting of acetonitrile and water (0.1% formic acid; 85:15, v/v) was delivered at a flow rate of 0.20 ml/min. DIM and the IS were eluted at 2.36 ± 0.04 and 2.43 ± 0.03 min, respectively. The total analysis time was 3.20 min. Atmospheric pressure chemical ionization was carried out using multiple reaction monitoring in the positive polarity mode. The ion transitions were set to m/z 247.1 → 130.1 (DIM) and 162.1 → 147.1 (IS). The method was successfully applied to the analysis of plasma samples after a single oral administration of the Indinol® Forto drug (200 mg) to healthy female Russian volunteers. Also, the developed method was used for the analysis of rabbit plasma samples after a single oral dose of DIM (20 mg/kg).     

2-Aryl-6-Polyfluoroalkyl-4-Pyrones as Promising RF-Building-Blocks: Synthesis and Application for Construction of Fluorinated Azaheterocycles

A convenient and general method for the direct synthesis of 2-aryl-6-(trifluoromethyl)-4-pyrones and 2-aryl-5-bromo-6-(trifluoromethyl)-4-pyrones has been developed on the basis of one-pot oxidative cyclization of (E)-6-aryl-1,1,1-trifluorohex-5-ene-2,4-diones via a bromination/dehydrobromination approach. This strategy was also applied for the preparation of 2-phenyl-6-polyfluoroalkyl-4-pyrones and their 5-bromo derivatives. Conditions of chemoselective enediones bromination were found and the key intermediates of the cyclization of bromo-derivatives to 4-pyrones were characterized. Synthetic application of the prepared 4-pyrones has been demonstrated for the construction of biologically important CF₃-bearing azaheterocycles, such as pyrazoles, pyridones, and triazoles.     

Theoretical Study of Twin Polymerization – From Chemical Reactivity to Structure Formation

Twin polymerization is a novel technique for synthesizing hybrid polymers with domain sizes in the nanometer range. While a broad variety of monomers have been investigated, the mechanistic details and the most important influences on the nanostructure formation are unknown. A scale bridging approach is presented to simulate the twin polymerization of 2,2'‐spirobi[4H‐1,3,2‐benzodioxasiline]. This approach is based on detailed quantum chemical calculations that yield insight into reactivity and structure at the molecular level while the kinetics of the network formation process and the influences that govern structure formation are investigated at the mesoscopic level by a coarse‐grained simulation.

     

Elementary explicit types and polynomial time operations

This paper studies systems of explicit mathematics as introduced by Feferman [9, 11]. In particular, we propose weak explicit type systems with a restricted form of elementary comprehension whose provably terminating operations coincide with the functions on binary words that are computable in polynomial time. The systems considered are natural extensions of the first‐order applicative theories introduced in Strahm [19, 20] (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Highly Efficient Photodegradation of Organic Pollutants Assisted by Sonoluminescence

The mechanism of the photodegradation of azo dyes via ultrasonication is studied using a combination of the high‐performance liquid chromatography and UV–vis spectroscopy with detailed analysis of the kinetics. Based on the kinetics studies of the sonodegradation, it was proposed that the degradation of azo dyes was a multistage process that involved: (1) the direct attack of azo bonds and phenyl rings of dyes by the sonochemically formed reactive oxygen species; (2) the activation of semiconductor particles by the light emitted during cavitation and the triggering of the photocatalytic pathways of dye degradation and (3) increase of the adsorption capacity of the semiconductor particles due to the sonomechanically induced interparticle collisions. The detailed kinetics study can help in following an effective process up‐scaling. It was demonstrated that extremely short pulses of light flashes in a cavitated mixture activated the surface of photocatalysts and significantly enhanced dye degradation processes.