Total synthesis of stevastelin B3

The total synthesis of stevastelin B3 was achieved using, as a key step, a method developed by us for the synthesis of 2-methyl-1,3-diols by Ti(III)-mediated diastereo- and regioselective opening of trisubstituted 2,3-epoxy alcohols, to carry out the stereoselective construction of its propionate-derived fatty acid segment.     

Chromotropic acid as fluorogenic reagent. I. Fluorimetric determination of beryllium

A highly sensitive and almost specific fluorimetric method has been developed for rapid determination of beryllium at ng/ml and sub-ng/ml levels with chromotropic acid as reagent at pH 4.8–6.0. The fluorescence intensity _ex = 362 nm, _em = 387 nm) is stable for 24 h. The calibration graph is linear over the range 0.1–60 ng/ml beryllium; a 1 1 complex is formed. Over sixty anions and cations, and some complexing agents such as EDTA, oxalate, tartrate, ascorbic acid, thiourea, phthalate, citrate, S₂O ₃ ^2– , SCN^– and salicylate do not interfere even when present in large excess. The method has been applied successfully for the determination of beryllium in ores, alloys, steels, environmental waters and in biological samples. The method is virtually specific and requires no preconcentration or clean-up steps.     

Characterization of micelles of polyoxyethylene nonylphenol (Igepal) and its complexation with 3,7-diamino-2,8-dimethyl- 5-phenylphenazinium chloride

This paper explores the association of a nonionic surfactant, Igepal (polyoxyethylene nonylphenol), in aqueous media by means of absorption and fluorescence spectroscopy. The critical micellar concentration (CMC) of the aggregate formed in the aqueous medium has been determined, using three different methods: UV-visible spectroscopy, fluorescence spectroscopy, and Stokes shift. The correlation of CMC with hydrophile-lipophile balance (HLB) indicates that the CMC decreases with decreased HLB. The obtained CMC values from different methods are close to each other and have allowed the determination of DeltaG values associated with the micellization. The association constant of the dye molecule Safranine T (ST) with the nonionic micelle of Igepal, aggregation number of the surfactant monomer, and location of the fluorophore in the micellar environment have been determined. The vertical ionization potential of Igepal, electron affinity of the dye, and degree of charge transfer from the micellar aggregate to the dye molecule have been determined by AM1 calculation. The experimental charge transfer transition energies are well correlated with the determined ionization potential values (ID) of Igepal. The degree of charge transfer (ground state complexes) has been found to be low. The polarity of the micelle solubilization sites has been estimated from the solvatochromic shift, Kosowar Z value, and ET30, and ETN values.     

LC–MS Simultaneous Determination of Itopride Hydrochloride and Domperidone in Human Plasma

A rapid, simple, sensitive and specific liquid chromatography–tandem mass spectrometry method was developed and validated for simultaneous quantification of itopride hydrochloride and domperidone in human plasma. Both drugs were extracted by liquid–liquid extraction with ethyl acetate and saturated borax solution. The chromatographic separation was performed on a reversed-phase C18 column with a mobile phase of water–methanol (2:98, v/v) containing 0.5% formic acid. The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The assay exhibited linearity over the concentration range of 3.33–500 ng mL⁻¹ for itopride hydrochloride and 3.33–100 ng mL⁻¹ for domperidone in human plasma. The precursor to product ion transitions of m/z 359.1–72.3 and 426.0–147.2 were used to measure itopride hydrochloride and domperidone respectively. The method was found suitable for the analysis of plasma samples collected during phase 1 pharmacokinetics study of itopride HCl 50 mg and domperidone 20 mg in 12 healthy volunteers after single oral doses of the combination drug.

     

Significant improvement in the pore properties of SBA-15 brought about by carboxylic acids and hydrothermal treatment

A comparative study of the pore properties of SBA-15 samples prepared under nonhydrothermal and hydrothermal conditions, in the absence and presence of carboxylic acids such as succinic, tartaric and citric acids has been carried out. In the absence of carboxylic acid, flake-like and spheroid particles were generally obtained irrespective of the preparative procedures. On the other hand, stirring of the pre-mix induces a rod-like morphology in presence of carboxylic acids. The samples prepared under non-hydrothermal conditions exhibit a higher degree of silicate condensation compared to those synthesized under hydrothermal conditions. SBA-15 samples prepared under hydrothermal conditions show higher values of the d (100) spacing independent of the presence of carboxylic acids. Presence of carboxylic acids as well as hydrothermal treatment improves the pore properties of SBA-15.     

Spectroscopic,structural, electrochemical,and cytotoxicity studies on dithiocarbamato-chelated ruthenium organometallics incorporating imine-phenol function

The heterogeneous phase reaction of [Ru(η²-RL)(PPh₃)₂(CO)Cl] (1) with the sodium salts of dimethyl dithiocarbamate (^MeDTC), diethyl dithiocarbamate (^EtDTC), and pyrrolidine dithiocarbamate (^PyrDTC) ligands led to the isolation of bright-yellow crystalline solids of type [Ru(η¹-RL)(PPh₃)₂(CO)(^R′DTC)] (2(R)(^R′DTC)) where η²-RL is C₆H₂O-2-CHNHC₆H₄R(p)-3-Me-5, η¹-RL is C₆H₂OH-2-CHNC₆H₄R(p)-3-Me-5, R is Me, OMe, Cl, and R^′ = Me, Et, Pyr. The binding of dithiocarbamate ligand is accompanied by the dissociation of Ru-O and Ru-Cl bonds along with concomitant prototropic shift from iminium–phenolato to imine–phenol motif. The reaction also involves a sterically controlled change in rotational conformation in going to the products. The X-ray crystal structure of [Ru(η¹-ClL)(PPh₃)₂(CO)(^EtDTC)] (2(Cl)(^EtDTC)) has been described here. An account of different spectral (UV–Vis, IR, NMR) and electrochemical data of the complexes are also asserted. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) analyses were performed to scrutinize the electronic structure and the absorption spectra of the complexes. One of the dithiocarbamato complexes has also been found to have in vitro antiproliferative properties against MDA-MB-231 breast cancer cell line which was determined by MTT assay. Cell death occurs mainly through apoptosis and flow cytometric analysis indicates that the complex induces cell cycle arrest in the sub G0/G1 phase.     

Inhomogeneous Bulk Viscous Fluid Universe with Electromagnetic Field and Variable ∧-Term

Cylindrically symmetric inhomogeneous cosmological model for bulk viscous fluid distribution with electro- magnetic field is obtained. The source of the magnetic field is due to an electric current produced along the z-axis. F12 is the non-vanishing component of electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion 0 in the model is proportional to the shear σ. The values of cosmological constant for these models are found to be small and positive at late time, which are consistent with the results from recent supernovae Ia observations. Physical and geometric aspects of the models are also discussed in presence and absence of magnetic field.     

Copper(II) α-hydroxycarboxylate complexes of bis(2-pyridylcarbonyl)amine ligand: From mononuclear complex to one-dimensional coordination polymer

The coordination geometry and supramolecular structures of three copper(II) complexes of two α-hydroxycarboxylates and one α-methoxycarboxylate with nitrogen donor co-ligands are discussed. The complexes have been characterized by elemental analysis, ESI-MS, IR and electronic spectroscopy, thermogravimetric analysis and magnetic measurements. The X-ray structure analysis of all the complexes, namely [(BPCA)Cu^II(MA)] (1), [(BPCA)Cu^II(MPA)(H₂O)] (2) and [(BPCA)Cu^II(BA)]_n (3), where BPCA = bis(2-pyridylcarbonyl)amidate, MA = racemic mandelate, MPA = racemic α-methoxy phenylacetate and BA = benzilate anion, shows the copper(II) ion in a distorted square-pyramidal geometry. In 1 the mandelate anion is coordinated to the copper(II) center in a bidentate fashion while in 2 the α-methoxycarboxylate is monodentate. In both cases a one-dimensional supramolecular array is formed through hydrogen bonds: the mononuclear units are directly connected in 1 by the MA hydroxyl group, whereas in 2 is the coordinated water that operates as H donor towards the MPA carboxylate group and the BPCA carbonyl oxygens of nearby complexes. In 3 the benzilate anion, acting as bridging ligand between copper ions, gives rise to a one-dimensional coordination polymer. In the latter, intra- and inter-chain π?π stacking interactions between pyridines and one phenyl ring of benzilate anions are observed in the packing.     

Zero-sum risk-sensitive stochastic games on a countable state space

Infinite horizon discounted-cost and ergodic-cost risk-sensitive zero-sum stochastic games for controlled Markov chains with countably many states are analyzed. Upper and lower values for these games are established. The existence of value and saddle-point equilibria in the class of Markov strategies is proved for the discounted-cost game. The existence of value and saddle-point equilibria in the class of stationary strategies is proved under the uniform ergodicity condition for the ergodic-cost game. The value of the ergodic-cost game happens to be the product of the inverse of the risk-sensitivity factor and the logarithm of the common Perron–Frobenius eigenvalue of the associated controlled nonlinear kernels.