Didemnaketals D and E,bioactive terpenoids from a Red Sea ascidian Didemnum species

Two new spiroketals, didemnaketals D (1) and E (2) were isolated from a marine ascidian species belonging to the genus Didemnum. The structures of the compounds were elucidated by extensive 1D (¹H, ¹³C, and DEPT) and 2D (COSY, TOCSY, HSQC, HMBC, NOESY, and ROESY) NMR studies and high-resolution mass spectroscopic data. The new didemnaketals differ from the reported ones in which that they lack the methyl functionality at C-6 and the hydroxy moiety at C-21. Instead, they possess an ester moiety at C-6 in addition to new oxygen functionality at C-20 of the didemnaketals. Compounds 1 and 2 were evaluated for their protein kinase inhibitory activity against different kinases (CDK5, CK1, DyrK1A, and GSK3) at 10 μg/mL. Compounds 1 and 2 showed moderate activity against these kinases. In addition, the compounds displayed moderate antimicrobial activity against Staphylococcus aureus and Bacillus subtilis, respectively.     

SYNTHESIS OF NEW RING SYSTEMS: ISOMERIC 1,2,4-TRIAZOLOPYRIMIDO [4″,5″:4′,5′]THIENO[3′,2′:5,6]PYRIDO[3,2C]CINNOLINES AND OTHER RELATED SYSTEMS

3-Amino-2-Cyano-4-(p-tolyl)thieno[3′,2′:5,6]pyrido[3,2-c]cinnoline 1 underwent ring closures with formamide and carbon disulphide to afford pyrimidothienopyridocinnaline 2 and its pyrimido-9,11-thione derivative 3, respectively. Treatment of 1 with triethylorthoformate followed by hydrazine hydrate produced 10-amino-11-imino-pyrimido system 5, which in turn reacted with triethylorthoformate, acetic acid, carbon disulphide, and acetylacetone to cyclize into the systems, 1,2,4-triazolo, 2-methyltriazolo, triazolo-2-thione, and 1,2,4-triazepinopyrimido thienopyridocinnolines 6– 8, 11, respectively. Similarly, 3-amino-2-carboxamido-thienopyridocinnoline 12 was reacted with triethylorthoformate to give pyrimidothienopyridocinnoline-11-one 13, which was treated with phosphorous oxychloride and then hydrazine hydrate to produce 11-hydrazinopyrimido system 16. Treatment of 16 with triethylorthoformate, acetic anhydride, carbon disulphide, and ethyl chloroformate afforded the systems, 1,2,4-triazolopyrimidothienopyrido-cinnoline derivatives 16– 18, 20, respectively.     

Supramolecular Self Assembly of [Cu(CN)4]3− Ions with Cationic {Ph3Sn+} Units in the Presence of Neutral Bidentate Ligands

The supramolecular interplay of the Ph ₃ Sn⁺ unit and the [Cu(CN) ₄ ]^3? ion with either 4,4′-bipyridine (bpy), trans-1,2-bis(4-pyridyl)ethene (tbpe), 1,2-bis(4-pyridyl)ethane (bpe), pyrazine (pyz), or methylpyrazine (mepyz) as bidentate ligands in presence of H ₂ O has been investigated for the first time. The products obtained have the general formula [(Ph ₃ Sn) ₃ Cu(CN)₄·L·XH₂O], where L is a bidentate ligand and X = 0–2. H ₂ O molecules are usually coordinated to tin atoms and are involved in two significant O─H─N hydrogen bonds, wherein the nitrogen atoms belong either to the bidentate ligand or the M-coordinated cyanide ligands. The structures of these supramolecular coordination polymers were investigated by elemental analysis, X-ray powder diffraction, and IR, mass, and NMR spectra.     

Radiation Synthesis of Superabsorbent Hydrogels Based on Chitosan and Acrylic Acid for Controlled Drug Release

Superabsorbent hydrogels based on the natural polymer chitosan and acrylic acid (CS/AAc) was prepared using ⁶⁰Co gamma radiation as a source of initiation and crosslinking. The factors, which affect the preparation of CS/AAc hydrogels such as irradiation dose, CS/AAc ratios, and acrylic acid monomer concentrations, to get the best optimum conditions, were investigated. The kinetic studies of the swelling of CS/AAc hydrogel showed that it follows a Fickian type of water diffusion. The Fickian constant value ‘n’ was more than 0.5 with a high swelling capacity of 300 g/g as superabsorbent hydrogel. In addition, the suitability of CS/AAc hydrogel as carrier material for the drug Chlortetracycline-HCl has been investigated by adsorption isotherm studies. The performance of drug release from hydrogel systems, influenced by acrylic acid ratio and the effect of pH of the medium was studied.     

Direct laser photo-induced fluorescence determination of bisphenol A

Classical photo-induced fluorescence methods are conducted in two steps: a UV irradiation step in order to form a photo-induced compound followed by its fluorimetric determination. Automated flow injection methods are frequently used for these analyses. In this work, we propose a new method of direct laser photo-induced fluorescence analysis. This new method is based on direct irradiation of the analyte in a fluorimetric cell in order to form a photo-induced fluorescent compound and its direct fluorimetric detection during a short irradiation time. Irradiation is performed with a tuneable Nd:YAG laser to select the optimal excitation wavelength and to improve the specificity. It has been applied to the determination of bisphenol A, an endocrine disrupter compound that may be a potential contaminant for food. Irradiation of bisphenol A at 230 nm produces a photo-induced compound with a much higher fluorescence quantum yield and specific excitation/emission wavelengths. In tap water, the fluorescence of bisphenol A increases linearly versus its concentration and, its determination by direct laser photo-induced fluorescence permits to obtain a low limit of detection of 17 μg L⁻¹.     

Nearly constant loss effect in sodium borate and silver meta-phosphate glasses: New insights

We present new insights into the Nearly Constant Loss (NCL) effect, which are based on a study of conductivity as a function of temperature and frequency in 0.3Na₂O · 0.7B₂O₃ and 0.5AgI · 0.5AgPO₃ glasses. In these systems, the ionic conductivity has been measured over a temperature range from 4 K to 475 K and in a frequency range from a few mHz to a few MHz. The conductivity spectra taken at various temperatures have then been mapped on to a representation of conductivity versus temperature (or inverse temperature) at fixed frequency. Indeed, such plots are often published in studies of the NCL effect. For a given system and a given frequency, an equivalent mapping is achieved by using suitable scaled model conductivity spectra derived from the MIGRATION concept. This enables us to identify, at fixed frequency, the temperature of transition from the ionic conductivity caused by the “ordinary” correlated hopping motion of the mobile ions (now known as the “first” universality) to the classical NCL behaviour (which Nowick termed “new” or “second” universality). We describe the details of our procedure and show that insights emerge with regard to both the high-frequency plateau of the conductivity component due to “ordinary” hopping and the NCL effect itself.     

Impact of ethylene carbonate on electrical properties of PVA/(NH4)2SO4/H2SO4 proton-conductive membrane

A new proton-conductive membrane (PCM) based on poly (vinyl alcohol) and ammonium sulfate (NH₄)₂SO₄ complexed with sulfuric acid and plasticized with ethylene carbonate (EC) at different weight percent were prepared by casting technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD patterns of all the prepared polymer electrolytes reveal the amorphous nature of the films. ac conductivity and dielectric spectra of the electrolyte were studied with changing EC content from weight 0.00 to 0.75 g. A maximum conductivity of 7.3 × 10⁻⁵ S cm⁻¹ has been achieved at ambient temperature for PCM containing 0.25 g of ethylene carbonate. The electrical conductivity σ, dielectric constant ε′ and dielectric loss ε″ of PCM in frequency range (100 Hz to 100 KHz), and temperature range (300–400 K) were carried out. Measurement of transference number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner’s polarization technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions. The electrolyte with the highest electrical conductivity was used in the fabrication of a solid-state electrochemical cell with the configuration (Mg/PCM/PbO₂). Various cell parameters ldensity, and current density were determined. The fabricated cells gave capacity of 650 μAh and have an internal resistance of 11.6 kΩ.     

Two-dimensional lattice Boltzmann simulations of vesicles with viscosity contrast

We present a numerical approach to simulate the dynamics of viscous vesicles (their internal and external fluids have different viscosities). The flow is computed using the lattice Boltzmann method and the fluid-vesicle two-way coupling is achieved using the immersed boundary method. The viscosity contrast (defined as the ratio of the internal to the external viscosities) is included using a geometrical algorithm that detects if a fluid node is either located inside or outside a vesicle. Our two-dimensional simulations successfully reproduce the tank-treading and tumbling dynamical states known for a viscous vesicle when it is subjected to simple shear flow. A good qualitative agreement between our simulation results and literature data is obtained. Moreover, we quantitatively analyze how inertia influences the dynamics of a vesicle and as an outlook we present an application of our method to the flow of multiple viscous vesicles in a microfluidic constriction.     

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Molecular rearrangements—XI: The acid-catalysed rearrangement of N-chloroacylarylamides

The rearrangement of N-chloroacetanilide in 99% acetic acid is compared with that of the N-chloro-derivatives of propionanilide, butyranilide, α-chloro, α-dichloro and α-trichloroacetanilides in presence of benzoic acid, toluene-p-sulphonic acid or hydrochloric acid as promoters.The rate of change increases progressively with increasing +I effect and decreases with increasing ?I effect of substituents on the acyl group.The rearrangements with different carboxylic acids and sulphonic acid catalysts are best interpreted as intermolecular chlorination, the protonated N-chloro-compounds acting as electrophilic chlorinating agents.