Studies on the Synthesis of (2R,4′R,8′R)-α-Tocopherol Alternative Syntheses of 2-Chroman-acetic Acid Intermediates

As an extension of previous studies on the total synthesis of (2R,4′R,8′R)-α-tocopherol ( 1 ) [1] [2], (S)-(?)-2-(6-benzyloxy-2,5,7,8-tetramethylchroman)acetic acid ( 6 ), a pivotal intermediate, possessing the absolute configuration required for construction of 1 was prepared by optical resolution of the racemic modification 11 . the latter substance was obtained by two routes, one emanating from the hydroxy acetal 7 [1] and the other based upon the Lewis acid mediated cycloaddition of trimethylhydroquinone to rac.-3-hydroxy-3-methylpent-4-en-l-yl acetate ( 16 ) giving rac. ethyl 2-(6-hydroxy-2,5,7,8-tetramethyl-chroman)acetate ( 12 ).     

Chemical characterization of the black crust present on the stone central portal of St. Denis abbey

 A black crust sample from the stony central portal of the abbey of St. Denis, France, was analyzed by chromatographic and spectroscopic techniques to determine whether it was due to atmospheric pollution or to the degradation of a past restoration treatment. Stratigraphic surveys by optical microscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersive X-ray fluorescence (SEM/EDX) and pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) were consistent in ascribing the bulk of the crust to gypsum (CaSO₄ ⋅ 2H₂O) with inclusion of carbon particulate. The organic fraction was a minor constituent of the black crust. Hence, the deterioration by an organic substance used in the past to restore the building was ruled out. Received: 23 May 1996/Revised: 29 July 1996/Accepted: 1 August 1996     

The ν1 and 2ν1 bands of DNSO

The infrared spectrum of DNSO has been recorded in the region of the N-D stretching fundamental vibration and of the first overtone. The results of the analysis are the following (in cm⁻¹):

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Breit and Quantum Electrodynamics Energy Contributions in Multielectron Atoms from the Relativistic Screened Hydrogenic Model

The correction to the Coulomb repulsion between two electrons due to the exchange of a transverse photon, referred to as the Breit interaction, as well as the main quantum electrodynamics contributions to the atomic energies (self-energy and vacuum polarization), are calculated using the recently formulated relativistic screened hydrogenic model. Comparison with the results of multiconfiguration Dirac-Hartree-Fock calculations and experimental X-ray energies is made.     

On the Projective Normality of Smooth Surfaces of Degree Nine

The projective normality of smooth, linearly normal surfaces of degree 9 in ^N is studied. All nonprojectively normal surfaces which are not scrolls over a curve are classified. Results on the projective normality of surface scrolls are also given.     

Poly(styrene-co-acrylonitrile) based proton conductive membranes

Sulfonated poly(styrene-co-acrylonitrile) (PSAN–SO₃H) membranes were obtained by sulfonation of the original styrene–acrylonitrile copolymer, in different molar ratios, and characterized by vibrational spectroscopy (FTIR), thermal analyses (TGA and DSC) and electrochemical impedance spectroscopy (EIS). The thermal stability of the sulfonated polymers exhibited a dependence on the sulfonation degree and reached 261 °C for samples up to 1:4 (sulfonating agent to styrene unit). FTIR spectra showed the covalent incorporation of sulfonic groups at the styrene units, confirming the PSAN–SO₃H formation. Vibrational spectra also indicated the presence of hydronium ions and dissociated sulfonic groups, indicating the existence of mobile protons for ion conduction. DSC analyses evidenced two glass transition temperatures (T_g), one associated with an ion-water domain and other with the chain backbone glass transition. The maximum conductivity of PSAN–SO₃H membranes at ambient temperature was about 10⁻³ Ω⁻¹ cm⁻¹, achieving 10⁻² Ω⁻¹ cm⁻¹ at 80 °C. The conductivity dependency on the temperature was found to be linear, similarly to other sulfonic acid polymers described on the literature, and the water uptake reaches 45.7% of the polymer mass, against 18.9% of the original copolymer.     

Ultrasensitive chemiluminescent immunochemical identification and localization of protein components in painting cross-sections by microscope low-light imaging

The characterization and localization of proteins and other organic components in the complex stratigraphy of paintings is crucial for authentication and studies of painting techniques. With this aim we have developed a new ultrasensitive immunochemical procedure for the detection of the protein ovalbumin (chicken egg white albumin), present in binding media or varnishes, in painting cross-sections. The technique is based on chemiluminescence imaging detection combined with optical microscopy, and allowed the sensitive localization of the target protein in cross-sections with high spatial resolution. In order to evaluate its performance, the method was first applied to standard samples (also containing different common pigments), then used for the localization of ovalbumin in samples obtained from a Renaissance wood painting.     

Antioxidant activity of diphenylpropionamide derivatives: synthesis, biological evaluation and computational analysis

We report the synthesis, antioxidant and antiproliferative activity and a QSAR analysis of synthetic diphenylpropionamide derivatives. Synthesis of these compounds was achieved by direct condensation of 2,2- and 3,3-diphenylpropionic acid and appropriate amines using 1-propylphoshonic acid cyclic anhydride (PPAA) as catalyst. Compound structures were elucidated by NMR analysis and their melting points were measured. The in vitro antioxidant activity of these compounds was tested by evaluating the amount of scavenged ABTS radical and estimating ROS and NO production in LPS stimulated J774.A1 macrophages. All compounds were tested for their effect on viability of cells and results demonstrated that they are not toxic towards the cell lines used. The cytotoxic activity of all compounds was evaluated by a Brine Shrimp Test.     

Insights into the Self-Filling Effects of Branched Isopropyl Groups on the Conformational and Supramolecular Properties of Isopropoxyprism[6]arene

In this work, the direct macrocyclization of a prism[6]arene macrocycle bearing branched alkyl chains on the rims is reported. Isopropoxyprism[6]arene adopts in solution and in the solid state a cuboid D₂-conformation in which four isopropyl groups are folded inside the cavity, to give C−H⋅⋅⋅π interactions and filling the internal void. The conformational features of isopropoxyprism[6]arene have been studied by dynamic ¹H NMR experiments. The presence of branched isopropyl chains on the prism[6]arene rims, stabilizes the cuboid D₂-conformation to a greater extent than ethyl or propyl groups in PrS[6]^Et and PrS[6]^nPr. The higher resistance of PrS[6]^iPr to open its cuboid D₂ conformation, with respect to PrS[6]^Et and PrS[6]^nPr, also affected its binding abilities. In fact, alkylammonium-based endo-cavity complexes of PrS[6]^iPr show lower binding constant values than the analogous propoxy/ethoxy-prism[6]arene complexes.     

Model-independent reconstruction of <Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">T</Emphasis>) teleparallel cosmology

We propose a model-independent formalism to numerically solve the modified Friedmann equations in the framework of f(T) teleparallel cosmology. Our strategy is to expand the Hubble parameter around the redshift \(z=0\) up to a given order and to adopt cosmographic bounds as initial settings to determine the corresponding \(f(z)\equiv f(T(H(z)))\) function. In this perspective, we distinguish two cases: the first expansion is up to the jerk parameter, the second expansion is up to the snap parameter. We show that inside the observed redshift domain \(z\le 1\), only the net strength of f(z) is modified passing from jerk to snap, whereas its functional behavior and shape turn out to be identical. As first step, we set the cosmographic parameters by means of the most recent observations. Afterwards, we calibrate our numerical solutions with the concordance \(\Lambda \)CDM model. In both cases, there is a good agreement with the cosmological standard model around \(z\le 1\), with severe discrepancies outer of this limit. We demonstrate that the effective dark energy term evolves following the test-function: \(f(z)={\mathcal {A}}+{\mathcal {B}}{z}^2e^{{\mathcal {C}}{z}}\). Bounds over the set \(\left\{ {\mathcal {A}}, {\mathcal {B}}, {\mathcal {C}}\right\} \) are also fixed by statistical considerations, comparing discrepancies between f(z) with data. The approach opens the possibility to get a wide class of test-functions able to frame the dynamics of f(T) without postulating any model a priori. We thus re-obtain the f(T) function through a back-scattering procedure once f(z) is known. We figure out the properties of our f(T) function at the level of background cosmology, to check the goodness of our numerical results. Finally, a comparison with previous cosmographic approaches is carried out giving results compatible with theoretical expectations.