Synthesis of 6-phenanthridinones and their heterocyclic analogues through palladium-catalyzed sequential aryl-aryl and N-aryl coupling

[reaction: see text] 6-Phenanthridinones and their heterocyclic analogues were synthesized through a one-pot procedure based on consecutive Pd-catalyzed aryl-aryl and N-aryl coupling from iodoarenes ortho-substituted by electron-releasing substituents and amides of o-bromoarene- and heteroarenecarboxylic acids.     

Thiol signalling network with an eye to diabetes

Redox regulatory system controls normal cellular functions. Controlled changes in redox couples potential serve as components for signal transduction, similarly to the phosphorylation cascade. Cellular redox biology requires both compartimentalisation and communication of redox systems: the thermodynamic disequilibrium of the major redox switches allows rapid and sensitive responses to perturbations in redox environments. The many oxidation states of sulphur are found in numerous sulphur species with distinct functional groups (thiols, disulphides, polysulphides, sulphenic, sulphinic and sulphonic acids, etc.), which participate in a complicated network of sulphur-based redox events. Human diseases such as diabetes mellitus and its cardiovascular complications have been associated with increased production of reactive oxygen species and perturbations of thiol redox homeostasis. The review surveys literature related to some etiopathogenic aspects and therapeutic perspectives. The dual toxic-protective property of sulphydryl-donor molecules in experimental settings proposes the general problem of designing antioxidants for therapeutic use.     

Determination of Olanzapine in rat brain using liquid chromatography with coulometric detection and a rapid solid-phase extraction procedure

A sensitive and selective method was developed for the determination of the antipsychotic drug Olanzapine levels in rat brain tissue, based on HPLC with electrochemical detection. The analyses were carried out on a C8 reversed phase column (150 mm x 4.6 mm, 5 microm), using a mobile phase composed of methanol and a phosphate buffer (44.0 mM, pH 3.5), containing triethylamine (21:79, v/v), flowing at 1.2 mL min(-1). A high sensitivity coulometric detection analytical cell containing two flow-through low volume working electrodes was used: electrode 1 was set at +0.350 V and electrode 2 at -0.200 V. Olanzapine, administered to rats in different doses or in different times, was extracted from tissue homogenate of either the whole brain or specific areas (cortex, hyppocampus, nucleus striatum) with a rapid solid phase extraction procedure (SPE) on Oasis HLB cartridges. The method provided a high extraction yield of Olanzapine and internal standard (2-methylolanzapine) from brain tissue homogenate with absolute recovery values higher than 90.0%. The detector response was linear over a concentration range of 0.2-100.0 ng mL(-1) of Olanzapine. The limit of quantification (LOQ) was 0.2 ng mL(-1). Precision results, expressed by the intra-day and the inter-day relative standard deviation values, were satisfactory, better than 4.6%. Accuracy was satisfactory as well. This method proved to be suitable for the analysis of Olanzapine in rat brain tissues and for the study of distribution and pharmacokinetics of Olanzapine in rat brain after a single treatment with the antipsychotic drug.     

The Norton–Simon hypothesis and the onset of non-genetic resistance to chemotherapy induced by stochastic fluctuations

By studying a simple but realistic biophysical model of tumor growth in the presence of a constant continuous chemotherapy, we show that if an extended Norton–Simon hypothesis holds, the system may have multiple equilibria. Thus, the stochastic bounded fluctuations that affect both the tumor carrying capacity and/or the drug pharmacodynamics (and/or the drug pharmacokinetics) may cause the transition from a small equilibrium to a far larger one, not compatible with the life of the host. In particular, we mainly investigated the effects of fluctuations that involve parameters nonlinearly affecting the deterministic model. We propose to frame the above phenomena as a new and non-genetic kind of resistance to chemotherapy.     

Facial selectivity in epoxidation of 2-cyclohexen-1-ol with peroxy acids. A computational DFT study

We addressed the mechanism of epoxidation of 2-cyclohexen-1-ol by locating all the transition structures (TSs) for the reaction of peroxyformic acid (PFA) with both pseudoequatorial and pseudoaxial cyclohexenol conformers (five TSs for each conformer) and, for purpose of comparison, also those for the PFA epoxidation of cyclohexene. Geometry optimizations were performed at the B3LYP/6-31G level, energies refined with single point B3LYP/6-311+G// B3LYP/6-31G calculations and solvent effects introduced with the CPCM method. Our results can be summarized as follows: (i) all TSs exhibit a spiro-like structure, that is, the dihedral angle between the peroxy acid plane and the forming oxirane plane is closer to 90 degrees than to 0 degrees (or 180 degrees ); (ii) there is a stabilizing hydrogen bonding interaction in syn TSs that, however, is partly counteracted by unfavorable entropic effects; (iii) syn,exo TSs with hydrogen bonding at the PFA peroxy oxygens are definitely more stable than syn,endo TSs hydrogen bonded at the PFA carbonyl oxygen; (iv) facial selectivity of epoxidation of both cyclohexenol conformers is mostly the result of competition between only two TSs, namely, an anti,exo TS and its syn,exo counterpart. The latter TS is more stable than the former one, as stabilization by hydrogen bonding overrides the unfavorable entropic and solvent effects; (v) calculations correctly predict both the experimental dominance of attack leading to syn epoxide for both cyclohexenol conformers and the higher syn selectivity observed for the pseudoequatorial as compared to the pseudoaxial derivative. Moreover, also the experimental relative and absolute epoxidation rates for cyclohexene and cyclohexenol as well as for pseudoaxial and pseudoequatorial cyclohexenol derivatives are fairly well reproduced by computational data.     

Cycoladdition of nitrile imines to cyclooctatetraene

Nitrile imines react with cyclooctatetraene and its diene adduct with dimethyl acetylene-dicarboxylate to yield cyclobutane-condensed pyrazoline systems. The different reactivity of cyclobutene and cyclohexadiene double bonds in the same molecule has been evaluated and compared with the reactivity toward other 1,3-dipoles. The thermolysis of the adducts has been described.     

The determination of iodine in materials of biological interest. A comparative evaluation of neutron-activation and automated colorimetric method

Two microanalytical methods for the determination of iodine in material of biological interest were studied: neutron-activation analysis and automated colorimetry (iodide catalysis of the As(III)-Ce(IV) system). The methods were applied to the analysis of samples of water, biological fluids, common salt and solid substances such as tissues, stools and foods. The particular procedures set up and optimized for the different substances with both methods are described and discussed, and the respective advantages in terms of sensitivity, accuracy, precision and speed are compared. The sensitivity and accuracy of both techniques were found to be quite adequate. Automated colorimetry is to be preferred for its precision and operative simplicity, while activation analysis retains full validity as a reference check method.