A short route to enantiomerically pure benzophenanthridinone skeleton: synthesis of lactone analogues of narciclasine and lycoricidine

Condensation of functionalized o-toluamide anions on a carbohydrate-derived lactone, followed by intramolecular aldol cyclization, provides enantiomerically pure 2-arylcyclohexenones. Different approaches for the stereoselective transformation of the carbonyl group of these key intermediates into an amino group were unsuccessful. However 1,4-addition of thiolate and concomitant ring closure to isocoumarine provided a useful method for the transformation of the tertiary amide function. Opening of the isocoumarin with ammonia provided the corresponding amide and recovery of the enone system. Subsequent reductive amination of this cyclohexenone was found to depend on the nature of the protecting groups and led to the protected form of 4-epi- and -iso-narciclasine. Oxo analogues of narciclasine and epi-narciclasine and lycoricidine were also obtained after reduction of the enone and subsequent lactonization. They showed no biological activity as antitumor agents.     

Copper(II) complexes of lipophilic aminoglycoside derivatives for the amino acid enantiomeric separation by ligand-exchange liquid chromatography

In this paper, a new class of ligand-exchange chiral stationary phase (LE-CSP) based on the copper complexes of lipophilic aminoglycoside derivatives was reported. Different stationary phases were developed by coating reversed-phase liquid chromatography supports with three neamine derivatives carrying a lipophilic octadecyl chain at the 4', 5 and 6 positions, respectively. The enantioselective ability of these LE neamine-based CSPs was evaluated and the 4'-derivative coated column was found to be the most interesting one for the amino acid resolution. The effects of the variation of several chromatographic parameters on the enantioseparation were evaluated in order to identify the analysis optimal conditions.     

Low-temperature Data for Carbon Dioxide

Summary. We investigated empirical data for the vapor pressure (154≤T≤196 K) and the heat capacity (12.52≤T≤189.78 K) of solid carbon dioxide. A computer algebra system (CAS) was used for all calculations. From the numerical point of view, we have adopted a cubic piecewise polynomial representation for the heat capacity and reached an excellent agreement between the available empirical data and the calculated ones. Furthermore, we have obtained values for the vapor pressure and heat of sublimation at temperatures below 195 right down to 0 K. The theoretical key prerequisites are: 1) Determination of the heat of sublimation of 26250 J · mol⁻¹ at vanishing temperature and 2) Elaboration of a ‘linearized’ vapor pressure equation that includes all the relevant properties of the gaseous and solid phases. It is shown that: 1) The empirical vapor pressure equation derived by Giauque & Egan remains valid below the assumed lower limit of 154 K (a similar argument holds for Antoine’s equation), 2) The heat of sublimation reaches its maximum value of 27211 J · mol⁻¹ at 58.829 K and 3) The vapor behaves as a (polyatomic) ideal gas even for temperatures below 150 K.     

Exceptional curves on smooth rational surfaces with not nef and of self-intersection zero

A -curve is a smooth rational curve of self-intersection , where is a positive integer. In 1998 Hirschowitz asked whether a smooth rational surface defined over the field of complex numbers, having an anti-canonical divisor not nef and of self-intersection zero, has -curves. In this paper we prove that for such a surface , the set of -curves on is finite but non-empty, and that may have no -curves. Related facts are also considered.

     

Irreducibility of the -classes on smooth rational surfaces

We give a characterization for a -divisor on a smooth rational surface to be irreducible under the assumption that an anticanonical divisor of is nef. Here is nef means for every effective divisor on , and a -divisor is a divisor such that the two numerical conditions hold.

As an application we give explicit examples of blowing up the projective plane at nine points infinitely near such that the obtained surface has an infinite number of -curves. A -curve is a smooth rational curve of self-intersection .

     

Allylic oxidation: easy synthesis of alkenones from activated alkenes with TEMPO

Activated alkenes and dienes are converted into the corresponding alkenone in excellent yields (>90%). In aqueous acetonitrile, the transformations are catalyzed by 2,2,6,6-tetramethyl-1-oxopiperidinium (TEMPO⁺) in the presence of water and 2,6-lutidine. TEMPO⁺ cations were regenerated electrochemically from the radical parent (TEMPO) at a vitreous carbon anode.     

Synthesis,structural studies and antituberculosis evaluation of new hydrazone derivatives of quinoline and their Zn(II) complexes

The quinoline hydrazone ligands were synthesized through multi-step reactions. The 2-hydroxy-3-formylquinoline derivatives (1a–1c) were prepared from acetanilide derivatives as starting materials using Vilsmeier–Haack reaction. Then the condensation of 2-hydroxy-3-formylquinoline derivatives with hydrazide derivatives (2a–2c) yielded quinoline hydrazone ligands (3a–3i). The synthesis of a new series of Zn(II) complexes carried out by refluxing with these quinoline hydrazone ligands (3a–3i) is reported. The molecular structures of the ligands (3a–3i) and the Zn complexes were characterized by elemental analysis and spectral studies like FT-IR, ¹H and ¹³C NMR, MS, UV–Visible and fluorescence. The preliminary results of antituberculosis study showed that most of the Zn(II) complexes 4a–4i demonstrated very good antituberculosis activity while the ligands 3a–3i showed moderate activity. Among the tested compounds 4e and 4g were found to be most active with minimum inhibitory concentration (MIC) of 8.00 μM and 7.42 μM respectively against Mycobacterium tuberculosis (H37 RV strain) ATCC No-27294 which is comparable to “first and second line” drugs used to treat tuberculosis.     

Enhancement in the supercapacitive storage performance of MnCO<Subscript>3</Subscript> using SiO<Subscript>x</Subscript> nanofluid-based electrolyte

Generally adopted strategies to improve capacitance of the electrode materials are tuning various properties of the electrode material or increasing the cell voltage. While tuning the properties of the electrode material is tedious, increasing the cell voltage is restricted by the stability of the electrolyte. Herein, we report a facile approach to improve the capacitance of MnCO₃ by the influence of SiO_x nanofluid in the electrolyte. The capacitance properties of MnCO₃ are studied in 0.1 M Mg(ClO₄)₂ electrolyte in the presence and in the absence of SiO_x nanofluid. The presence of small amount of SiO_x nanofluid in the electrolyte provides higher diffusivity and more conductive percolation paths for ions and thus decreases internal resistance and increases ionic conductivity of the electrolyte. As a result, 60% enhancement in the capacitance is witnessed for MnCO₃. Further, nanofluid containing electrolyte is found to be stable over a month.

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Graphical abstract Improvement in the capacitance properties of MnCO by the influence of SiO nanofluid

     

Refining the Hermite-Hadamard inequalities for operator convex maps in multiple operator variables

Intensive studies aiming to extend the Hermite-Hadamard inequalities and to explore some properties and applications of these inequalities have been carried out recently. The contribution of this paper falls within this framework. We investigate here some refinements of the Hermite-Hadamard inequalities for operator convex maps involving multiple operator arguments.