A novel synthesis of (±)-descarboxyquadrone

The novel synthesis of descarboxyquadrone (3) and its model compound (4) by using the acid-catalyzed rearrangement of [4.3.2]propellanones is described.     

Facile preparation of an α-Keggin-type [H3W12O40] complex: Does it exist in aqueous solution?

The formation processes of α-Keggin-type [H₂W₁₂O₄₀]⁶⁻ and [H₃W₁₂O₄₀]⁵⁻ complexes were investigated in aqueous W^VI (0.05–0.50 M) solutions. The formation of [H₂W₁₂O₄₀]⁶⁻ was ascertained by the appearance of a ¹⁸³W NMR line at −117 ppm, but no evidence was found for the existence of [H₃W₁₂O₄₀]⁵⁻ in the solution at the accessible pH range. The addition of (CH₃)₄N⁺ (Me₄N⁺) to the W^VI solution directly precipitated the (Me₄N)₆[H₂W₁₂O₄₀] salt. On the other hand, the addition of the larger Bu₄N⁺ cation precipitates the (Bu₄N)_4.5H_0.5[H₃W₁₂O₄₀] salt, because a naked proton formed during the crystallization process or in the solid state may enter into the Keggin shell to produce [H₃W₁₂O₄₀]⁵⁻. This explanation is based on the fact that [H₂W₁₂O₄₀]⁶⁻ is not spontaneously converted into [H₃W₁₂O₄₀]⁵⁻ in acidified aqueous solution. On the basis of their voltammetric properties, a simple diagnostic criterion was developed to distinguish between [H₂W₁₂O₄₀]⁶⁻ and [H₃W₁₂O₄₀]⁵⁻.     

Synthesis and spectral properties of polymethine-cyanine dye-nitroxide radical hybrid compounds for use as fluorescence probes to monitor reducing species and radicals

Various hybrid compounds comprised of two types of nitroxide radicals and either a pentamethine (Cy5) or trimethine cyanine (Cy3) were synthesized. The nitroxide radicals were linked either via an ester-bond to one or two N-alkyl carboxyl-terminated groups of Cy5, or via two amido-bonds (aminocarbonyl or carbonylamino group) to the 5-position of the indolenine moieties of Cy5 and Cy3. Changes in fluorescence and ESR intensities of the hybrid compounds were measured before and after addition of Na ascorbate in PBS (pH 7.0) to reduce the radicals. Among the hybrid compounds synthesized, those that linked the nitroxide radicals via an aminocarbonyl residue at the 5-position of the indolenine moieties on Cy5 and Cy3 exhibited a 1.8- and 5.1-fold increase in fluorescence intensity with the reduction of the nitroxide segment by the addition of Na ascorbate, respectively. In contrast, fluorescence intensity was not enhanced in the other hybrid compounds. Thus, the hybrid compounds which exhibited an increase in fluorescent intensity with radical reduction can be used in the quantitative measurement of reducing species such as Fe(2+) and ascorbic acid, and hydroxyl radicals. Because these hybrid compounds have the advantage of fluorescing at longer wavelengths-661 (Cy5) or 568 (Cy3)nm, respectively, they can be used to measure radical-reducing species or radicals either in solution or in vivo.     

Orthogonal trap time-of-flight mass spectrometer using a collisional damping chamber

We report a new hybrid mass spectrometer, which is a combination of a quadrupole ion trap and an orthogonal time-of-flight (TOF) mass spectrometer. This new configuration consists of a collisional-damping chamber (CDC) inserted between an MSn-capable ion trap and a high-mass-accuracy orthogonal-TOF mass spectrometer. Because the CDC converted an ion packet into an energy-focused and quasi-continuous beam, a high mass resolution of over 10,000 and a high mass accuracy of better than 3 ppm were achieved. Moreover, the ratio of the maximum detectable m/z to the minimum detectable m/z, which is referred to here as the mass window, was improved to more than 10.     

Preparation of hemispherical hollow silica microcapsules with different affinity surface by using spherical vaterite calcium carbonate as template

We developed a method to prepare hemispherical hollow silica microcapsules (HHSM) with different affinity surfaces using spherical vaterite calcium carbonate (SVCC) as a template. The preparation process composed of the adhesion of calcium carbonate onto the surface of methyl methacrylate (MMA) droplets followed by suspension polymerization, the partial etching of calcium carbonate on the polymethyl methacrylate (PMMA) mother particle, the formation of silicon dioxide powder by sol–gel reaction and their deposition onto the etched flat surface of calcium carbonate, the surface modification of deposited silicon dioxide with silane coupling agent, the removal of the mother particle with acetone, the formation of silicon dioxide powder by sol–gel reaction and deposition onto the exposed hemispherical surface of calcium carbonate, and the surface modification of deposited silicon dioxide with silane coupling agent. The synthesized microcapsules had a complete hemispherical structure and both hydrophilic and hydrophobic surfaces. Copyright © 2007 John Wiley & Sons, Ltd.     

Chemo-enzymatic synthesis of fluorinated 2-N-acetamidosugar nucleotides using UDP-GlcNAc pyrophosphorylase

Two non-natural fluorinated 2-N-acetamidosugar nucleotides, uridine 5'-diphosphate (UDP) 2-acetamido-2,4-dideoxy-4-fluoro-alpha-D-glucopyranose (UDP-4-FGlcNAc) 1 and its galacto isomer (UDP-4-FGalNAc) 2, were enzymatically constructed by treating chemically synthesized fluorinated 2-N-acetamidosugar 1-phosphates as the donor with UDP 2-acetamido-2-deoxy-alpha-D-glucopyranose pyrophosphorylase in the presence of uridine 5'-triphosphate (UTP).     

On the mixed complexes of tetracycline metal chelates

The mixed complexes of chlorotetracycline-metal chelates with isomazid, penicillin G, and dihydrostreptomycin were examined with Th⁺⁴, Cu⁺², Fe⁺³, Co⁺³, and Ni⁺² ions.A mechanism is proposed that accounts for the formation of the mixed complexes, cationic chelates of tetracycline have a molar ratio of 1 : 1 of metal to chlorotetracycline and mixed complexes are formed by combining with other ligands through the remaining covalencies. The properties and preparation of the mixed complexes are given