Raman spectroscopic study of tungsten(VI) oxosulfato complexes in WO3-K2S2O7-K2SO4 molten mixtures: stoichiometry, vibrational properties, and molecular structure

The dissolution reaction of WO3 in pure molten K2S2O7 and in molten K2S2O7-K2SO4 mixtures is studied under static equilibrium conditions in the XWO3(0) = 0-0.33 mol fraction range at temperatures up to 860 °C. High temperature Raman spectroscopy shows that the dissolution leads to formation of W(VI) oxosulfato complexes, and the spectral features are adequate for inferring the structural and vibrational properties of the complexes formed. The band characteristics observed in the W=O stretching region (band wavenumbers, intensities, and polarization characteristics) are consistent with a dioxo W(=O)2 configuration as a core unit within the oxosulfato complexes formed. A quantitative exploitation of the relative Raman intensities in the binary WO3-K2S2O7 system allows the determination of the stoichiometric coefficient, n, of the complex formation reaction WO3 + nS2O7(2-) --> C(2n-). It is found that n = 1; therefore, the reaction WO3 + S2O7(2-) > WO2(SO4)2(2-) with six-fold W coordination is proposed as fully consistent with the observed Raman features. The effects of the incremental dissolution and presence of K2SO4 in WO3-K2S2O7 melts point to a WO3 · K2S2O7 · K2SO4 stoichiometry and a corresponding complex formation reaction in the ternary molten WO3-K2S2O7-K2SO4 system according to WO3 + S2O7(2-) + SO4(2-) --> WO2(SO4)3(4-). The coordination sphere of W in WO2(SO4)2(2-) (binary system) is completed with two oxide ligands and two chelating sulfate groups. A dimeric [{WO2(SO4)2}2(μ-SO4)2](8-) configuration is proposed for the W oxosulfato complex in the ternary system, generated from inversion symmetry of aWO2(SO4)3(4-) moiety resulting in two bridging sulfates. The most characteristic Raman bands for the W(VI) oxosulfato complexes pertain to W(=O)2 stretching modes (i) at 972 (polarized) and 937 (depolarized) cm(-1) for the ν(s) and ν(as) W(=O)2 modes of WO2(SO4)2(2-), and (ii) at 933 (polarized) and 909 (depolarized) cm(-1) for the respective modes of [{WO2(SO4)2}2(μ-SO4)2](8-).     

Synthesis of novel PPARα/γ dual agonists as potential drugs for the treatment of the metabolic syndrome and diabetes type II designed using a new de novo design program PROTOBUILD

Peroxisome proliferator activated receptors (PPARs) have been shown to have critical roles in fatty acid oxidation, triglyceride synthesis, and lipid metabolism - making them an important target in drug discovery. Here we describe the in silico design, synthesis and in vitro characterisation of a novel series of 2,5-disubstituted indoles as PPARα/γ dual agonists. PPAR activation assays are performed with known agonists diazabenzene (WY14.643), aminopyridine (BRL49653) and bisaryl (L165.041), as positive controls. All the indole compounds synthesized are found to be active PPARα and PPARγ agonists, with particular efficacy from those with 2-naphthylmethyl substitution. This is a useful demonstration of a new de novo design methodology implemented by the protobuild program and its ability to rapidly produce novel modulators for a well characterized drug target.     

The Rearrangement of 2,2‐Diphenyl‐1‐[(E)‐2‐phenylethenyl]cyclopropane to 3,4,4‐Triphenylcyclopent‐1‐ene: a DFT Analysis

A computational study on the rearrangement of 2,2‐diphenyl‐1‐[(E)‐2‐phenylethenyl]cyclopropane ( 1 ) is presented, using density functional theory (DFT), (U)B3LYP with the 6‐31G* basis set (DFT1) and (U)M05‐2X with the 6‐311+G** basis set (DFT2). In agreement with a biradical character of the transition structure (TS) or intermediate, the potential‐energy hypersurface is lowered by the influence of three conjugated Ph groups. Surprisingly, two conformations of the geminal diphenyl group (different twist angles) induce two different minimum‐energy pathways for the rearrangement. Independent of the functional used, the first hypersurface harbors true biradical intermediates, whereas the second energy surface is a flat, slightly ascending slope from the starting material to the TS. The functional (U)M05‐2X with the basis set 6‐311+G** provides realistic energies which seem to be close to experiment. The activation energy for racemization of enantiomers of 1 is lower than that of rearrangement by 2.5 kcal mol^?1, in agreement with experiment.     

An efficient synthesis of 3-(N-piperidinemethyl)-2,2,5,5-tetramethyl-1-oxy-3-pyrroline,a promising radioprotector for cancer radiotherapy

Nitroxides can ameliorate the toxic effects of radiation during cancer therapy. Nitroxides are paramagnetic and can be used in magnetic resonance imaging (MRI) and electron paramagnetic resonance imaging (EPRI) to monitor in vivo oxidative stress status. Compound 5 (3-(N-piperidinemethyl)-2,2,5,5-tetramethyl-1-oxy-3-pyrroline) was found to be the most effective nitroxide radioprotector. An efficient synthesis for this promising radioprotector was developed.     

On-line coupling of sequential injection extraction with restricted-access materials for sample clean-up and analysis of drugs in biological matrix

In this contribution, the on-line coupling of solid phase extraction (SPE), based on a restricted-access material (RAM), with sequential injection technique (SIA) for the analysis of biological samples, is described. The SIA-RAM system was tested with a new potential antileucotrienic drug (VUFB-19363 (Quinlukast)) for serum analysis. The method is based on SPE with the novel internal-surface reversed-phase column packing material-alkyl-diol silica (ADS). The supports tolerate direct and repetitive injection of proteinaceous fluids (plasma, serum) and allow reversed-phase partitioning at the internal surface. A column packed with a 25 microm C18 alkyl-diol support was used for direct serum injection. Using a 6-port selection valve and the system of three mobile phases, the polar matrix compounds and metabolites are removed by sequentially aspirated mobile phases with lower content of the organic part (methanol-water (2:98) and following acetonitrile-water (20:80)) to the waste, and then, the analyte enriched on the column is eluted by a strong mobile phase (acetonitrile-methanol-water (40:20:40)) to the UV detector without transfer loss. With the fully automated SIA system, a total analysis time of less than 10 min was achieved. The only off-line sample pre-treatment step required to remove particulate matter was centrifugation. The studies showed a range of linearity (2-40 microg ml(-1)) and a high recovery (93.6-96.8%) of drug from the biological matrix with coefficients of variation (RSD) less than 5.0% (n = 6). This paper introduces a new, simple and robust analytical technique suitable for screening determination and direct analysis of drugs in biological materials.     

Thioformaldehyde S-methylide and thioacetone S-methylide: an ab initio MO study of structure and cycloaddition reactivity

The mechanisms of cycloaddition of thioformaldehyde S-methylide and thioacetone S-methylide, as models for an alkyl-substituted ylide, to thioformaldehyde and thioacetone, as well as to ethene as a model for a C=C double bond have been studied by ab initio calculations. Restricted and unrestricted B3LYP/6-31G* calculations were performed for the geometries of ground states, transition structures, and intermediates. Although basis sets with more polarization functions were tested, the 6-31G* basis set was applied throughout. Single-point CASPT2 calculations are reported for analysis of the unsubstituted system. The stabilities of structures with high biradical character seem to be overestimated by DFT methods in comparison to CASPT2. The general trends of the results are independent of the level of theory. Thioformaldehyde adds to thioformaldehyde S-methylide without activation energy, and the activation energies for two-step biradical pathways to 1,3-dithiolane are low. C,S biradicals are more stable than C,C biradicals. The two-step cycloaddition is not competitive with the concerted cycloaddition. Methyl substitution in the 1,3-dipole and the dipolarophile does not change the mechanistic relationships. TSs for the concerted formation of the regioisomeric cycloadducts of thioacetone Smethylide and thioacetone were located. Concerted addition remains the preferred reaction. The reactivity of the C=S double bond is high relative to that of the C=C double bond.     

Asymmetric synthesis of (R)-reticuline. A new strategy for the asymmetric synthesis of isoquinolines via enantioselective epoxidation or dihydroxylation

A new strategy for the asymmetric synthesis of 1-benzyl-1,2,3,4-tetrahydroisoquinolines7 − 9 has been developed. The route involves introduction of asymmetry via enantioselective epoxidation or dihydroxylafion of corresponding stilbene precursors followed by aminolysis and Pomeranz-Fritsch cyclization. The strategy has been successfully applied to the asymmetric synthesis of (R)-reticuline (9), the key-intermediate in the synthesis of morphine alkaloids on the biomimetic route.     

EARLY CELL KINETIC EFECTS OF A SINGLE DOSE OF NARROW-BANDED ULTRAVIOLET B IRRADIATION ON THE RAT CORNEAL EPITHELUM

Abstract— The right eyes of 40 rats were exposed to a signal erythemogenic dose fo ultraviolet B irradiation (UVB) at 297nm. The irradiation was directed perpenddicualr to the center of the cornea. The left eyes served as controls. The animals were randomly assigned into 10 groups. The labelling index (LI) after pluse labeling the tritiated thymidine and the mitotic rate (MR) after Colcemid administration were registered in the corneal epithelium at predetermined intervals up to 96 h after the irradiation. A mathematical method was used to corealted corresponding corneal areas from the different animals. In the central the LI was considerably reduced up to 36h after the irradiation. The LI increased toward the peripheral cornea and reached normal values at the limbal area. The MR was also reduced up to 36h. However, this reduction was over the entire epithelium. The block in cell proliferation was followed by increased proliferation.