Leishmanicidal active withanolides from a pakistani medicinal plant, Withania coagulans

In the course of screening for leishmanicidal constituents from Asian and South American medicinal plants, a Pakistani medicinal plant, Withania coagulans, showed activity. We therefore studied the active components of the methanol extract of aerial parts of W. coagulans. From the ethyl acetate soluble fraction of the extract, four new withanolides (1-4) were isolated along with seven known withanolides (5-11). The new compounds were elucidated to be (14R,15R,17S,20S,22R)-14,15,17,20-tetrahydroxy-1-oxowitha-2,5,24-trienolide (1), (14R,15R,17S,20S,22R)-14,15,17,20-tetrahydroxy-1-oxowitha-3,5,24-trienolide (2), (14S,17R,20S,22R)-14,17,20-trihydroxy-1-oxowitha-2,5,24-trienolide (3), and (14S,17R,20S,22R)-14,17,20-trihydroxy-1-oxowitha-3,5,24-trienolide (4), from 1H-NMR, 13C-NMR, 2D-NMR and high resolution (HR)-MS data. Some of these compounds having the partial structure 1-oxo-2,5-diene showed strong leishmanicidal activity against Leishmania major.     

Synthesis of pyrrolophenanthridone alkaloid kalbretorine from indolecarboxylic acids via hypervalent iodine(III) mediated halodecarboxylation and reduction

The treatment of 8,9,10-trimethoxy-7H-pyrrolo[3,2,1-de]phenanthridine-4,5-dicarboxylic acid with phenyliodine diacetate and potassium iodide in tetrahydrofuran gave the corresponding 4,5-diiodo derivative, which was converted to kalbretorine via reduction, demethylation, followed by alkylation.     

Effect of aggregation on the excited-state electronic structure of perylene studied by transient absorption spectroscopy

The effect of aggregation on the excited-state electronic structure of perylene was studied through transient absorption measurements of isolated molecules, excimers, monomeric crystals (beta-perylene), and dimeric crystals (alpha-perylene). Changes of electronic state were clearly identified from the changes in transient absorption spectra. A detailed investigation was made by combining the obtained results with previous measurements of ground-state absorption and fluorescence spectra. The energy level of the ion-pair state in alpha-perylene crystals was estimated, and the results are compared with previous photoconductivity results. Moreover, the relaxation processes of excited states in alpha-perylene crystals were studied by femtosecond transient absorption measurements.     

Conformation-controlled luminescent properties of lanthanide clusters containing p-tert-butylsulfonylcalix[4]arene

Dinuclear and cubane-shaped lanthanide cluster complexes containing EuIII)and TbIII were synthesized by step-by-step construction using p-tert-butylsulfonylcalix[4]arene as a cluster-forming ligand. The sulfonylcalixarene adopts a pinched-cone conformation in the dinuclear complexes and a cone conformation in the cubane complexes. Because the calixarene has a large pi-conjugate system expanding over the entire molecule, it behaves as a good antenna chromophore for UV and near-UV light, and a slight conformational change of the calixarene (from cone to pinched-cone and vice versa) has an effect on the energy levels of excited S1 and T1 states. As a result, selectivity is observed in the luminescent properties of dinuclear and cubane-shaped systems of EuIII and TbIII.     

E- or Z-selective Knoevenagel condensation of acetoacetic derivatives: effect of acylated substituent, that is, TEMPO and amines, as an auxiliary, and new accesses to trisubstituted E- and Z-2-alkenals and furans

Knoevenagel condensation of O-acetoacetylTEMPOs (2,2,6,6-tetramethylpiperidine-1-oxyl) with aldehydes substituted with an electron-withdrawing group such as aromatic and heteroaromatic ones leads preferentially to E-adducts, while acylacetoamides including Weinreb amides produce Z-adducts, exclusively. These E- and Z-adducts are selectively converted to the corresponding (2E)- and (2Z)-2-hyroxyalkyl-2-alkenals, respectively, by stepwise reductions of the acyl group with DIBALH and then the carboxylic functions after protection of the hydroxy group. Transformation of the Knoevenagel products by taking advantage of the E-geometry to trisubstituted furans is also developed.     

Application of approximations for joint cumulative k-distributions for mixtures to FSK radiation heat transfer in multi-component high temperature non-LTE plasmas

Approximations for joint cumulative k-distribution for mixtures are efficient for full spectrum k-distribution (FSK) computations. These approximations provide reduction of the database that is necessary to perform FSK computation when compared to the direct approach, which uses cumulative k-distributions computed from the spectrum of the mixture, and also less computational expensive when compared to techniques in which RTE's are required to be solved for each component of the mixture. The aim of the present paper is to extend the approximations for joint cumulative k-distributions for non-LTE media. For doing that, a FSK to non-LTE media formulation well-suited to be applied along with approximations for joint cumulative k-distributions is presented. The application of the proposed methodology is demonstrated by solving the radiation heat transfer in non-LTE high temperature plasmas composed of N, O, N₂, NO, N₂⁺ and mixtures of these species. The two more efficient approximations, that is, the superposition and multiplication are employed and analyzed.     

From organic conductors to bio-conductors

Two major categories of organic solids are known to offer the prospect of electrical conduction. One of them consists of charge-transfer complexes such as BEDT-TTF salts. A large number of studies on charge-transfer complexes have been carried out and their conductivity ranges from semiconductor to superconductor. The other group comprises single component materials. Typical examples are polycyclic aromatic compounds and also phthalocyanines; their conductivities are not as good as those of the donor-acceptor kinds.¹⁾ As one of those single component organic semiconductors, a group of cytochromes, electron carrier in biological system, was offered. Cytochrome c₃ (molecular weight = 13,995, 107 amino acid residers), an electron carrier in the reactions of very negative potentials in cells of Desulfovibrio, has four homes in the molecule.