A Diastereoselective Synthesis of Functionalized Tetrahydroindeno[2′,1′,3,4]pyrido[2,1‐a]isoquinolines

An effective route to alkyl 9a‐(2,3‐dihydro‐1,3‐dioxo‐1H‐inden‐2‐yl)‐9a,14,14a,14b‐tetrahydro‐14‐oxoindeno[2′,1′:3,4]pyrido[2,1‐a]isoquinoline‐9‐carboxylates via a diastereoselective one‐pot four‐component reaction of isoquinoline and alkyl prop‐2‐ynoates with two equivalents of indane‐1,3‐dione, in aqueous MeOH at room temperature, is described.     

Focused grid‐based resampling for protein docking and mapping

The fast Fourier transform (FFT) sampling algorithm has been used with success in application to protein‐protein docking and for protein mapping, the latter docking a variety of small organic molecules for the identification of binding hot spots on the target protein. Here we explore the local rather than global usage of the FFT sampling approach in docking applications. If the global FFT based search yields a near‐native cluster of docked structures for a protein complex, then focused resampling of the cluster generally leads to a substantial increase in the number of conformations close to the native structure. In protein mapping, focused resampling of the selected hot spot regions generally reveals further hot spots that, while not as strong as the primary hot spots, also contribute to ligand binding. The detection of additional ligand binding regions is shown by the improved overlap between hot spots and bound ligands. © 2016 Wiley Periodicals, Inc.     

Fluidized Bed Polyethylene Reactor Modeling in Condensed Mode Operation

Summary: Modeling of fluidized bed reactor for polyethylene production in the condensed mode operation is proposed in this paper. A two-phase model including the emulsion and bubble phases with the constant bubble size is employed to describe hydrodynamic behavior of the reactor. The kinetics of Ziegler-Natta polymerization is also modeled with a two active site model. The phase behavior and solubility of low molecular weight components in polyethylene are estimated with the Sanchez-Lacombe equation of state. The validation of the model is carried out with industrial data for an ethylene and 1-butene copolymerization with the isopentane as a condensable component. The simulation results are in good agreement with industrial data. The model is also used to study quantitatively the effect of the inlet stream temperature to the reactor and isopentane concentration in the reactor on the production rate. For instance, in a typical process, when the inlet stream temperature changes 10 °C, the production rate will alter about 40%. Furthermore, the change of the isopentane concentration around 1 mole percentage leads to a variation of production rate about 14%.     

Cellulose-Based Composites as Scaffolds for Tissue Engineering: Recent Advances

Today, numerous studies have focused on the design of novel scaffolds for tissue engineering and regenerative medicine applications; however, several challenges still exist in terms of biocompatibility/cytocompatibility, degradability, cell attachment/proliferation, nutrient diffusion, large-scale production, and clinical translation studies. Greener and safer technologies can help to produce scaffolds with the benefits of cost-effectiveness, high biocompatibility, and biorenewability/sustainability, reducing their toxicity and possible side effects. However, some challenges persist regarding their degradability, purity, having enough porosity, and possible immunogenicity. In this context, naturally derived cellulose-based scaffolds with high biocompatibility, ease of production, availability, sustainability/renewability, and environmentally benign attributes can be applied for designing scaffolds. These cellulose-based scaffolds have shown unique mechanical properties, improved cell attachment/proliferation, multifunctionality, and enhanced biocompatibility/cytocompatibility, which make them promising candidates for tissue engineering applications. Herein, the salient developments pertaining to cellulose-based scaffolds for neural, bone, cardiovascular, and skin tissue engineering are deliberated, focusing on the challenges and opportunities.     

Stability study of the gastric floating dosage form of capecitabine

Since administration of capecitabine tablets leading to dose limiting makes the unfavorable toxicity, preparation of sustained-release tablets will overcome most of these side effects. The aim of this study was to prepare and study the stability of capecitabine sustained-release tablets. Sustained-release tablets of capecitabine were characterized by differential scanning calorimetry, X-ray diffraction, and infrared and ultraviolet spectroscopy techniques to determine the stability of the tablets. All tests carried out for tablets upon preparation as well as 6 and 12 months after preparation. The gradual decomposition of capecitabine sustained-release tablets stored at accelerated conditions (40 °C in 75 % of relative humidity) was indicated by decreasing values of peak purity and melting temperature, calculated from the Van’t Hoff equation. Except for the occurrence of one sharp peak for long-term stability and some sharp peaks in the accelerated condition, all peaks showed a crystallized nature. But the FTIR and UV results showed that there were no changes between the initial sustained-release tablets and stored tablets. Although the XRD results showed more peaks in the accelerated condition tablets, the crystalline form of capecitabine was maintained. These findings demonstrate that the capecitabine sustained-release tablet has excellent stability in normal and long-term storage conditions, with slight changes in the accelerated condition.     

A new image encryption method: parallel sub-image encryption with hyper chaos

A new image encryption scheme, based on a total shuffling and parallel encryption algorithm is proposed in this paper. Two chaotic systems have been used in the encryption algorithm to confuse the relationship between the plain-image and the cipher-image. To make the encryption procedure more confusing and complex, the plain-image is first divided into 4 sub-images and then the position of each sub-image is changed pseudo-randomly according to a logistic map. Next, a total shuffling matrix is used to shuffle the position of pixels in the whole image and then sub-images are encrypted simultaneously in a parallel manner. The experimental results on USC data base demonstrate that the proposed encryption algorithm has a low time complexity and has the advantages of large key space and high security. Moreover, the robustness of this locally encryption method is much more in contrast with other encryption schemes and the distribution of gray values has a random-like behavior in the encrypted image.     

A one-pot synthesis of piperidinium spirooxindoline-pyridineolates and indole-substituted pyridones in aqueous or ethanol medium

Molecular Diversity - Piperidinium spirooxindoline-pyridineolate has been prepared via one-pot multicomponent reaction of isatin, malononitrile, cyanoacetohydrazide, and piperidine in water or...     

An inorganic–organic hybrid material based on a Keggin-type polyoxometalate@Dysprosium as an effective and green catalyst in the synthesis of 2-amino-4H-chromenes via multicomponent reactions

A novel inorganic–organic hybrid, [Dy₄(PDA)₄(H₂O)₁₁(SiMo₁₂O₄₀)]·7H₂O denoted as (POM@Dy-PDA), based on a lanthanide cluster, a Keggin-type polyoxomolybdate, and PDA (1,10-phenanthroline-2,9-dicarboxylic acid) was prepared and fully characterized by elemental analysis, Fourier-transform infrared and UV–Vis spectroscopies, thermogravimetric analysis, powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. The structural analysis study showed that the [SiMo₁₂O₄₀]⁴⁻ ions reside in the interspace between two cationic layers as discrete counterions and are not coordinated to the rare-earth ions. Significantly, this hybrid catalyst is a rare case of an inorganic–organic hybrid polyoxometalate (POM) with a PDA ligand based on CSD search (CSD version 5.40/November2018). The hybrid catalyst was further characterized via powder X-ray diffraction (PXRD) pattern at room temperature which indicated the good phase purity of the catalyst. BET and Langmuir surface area analysis indicate surface area of POM@Dy-PDA 6.6 and 51.3 m2g-1, respectively. The catalytic activity of the hybrid catalyst was successfully examined in the synthesis of 2-amino-4H-chromene derivatives through a multicomponent reaction. A three-component, one-pot reaction involving differently substituted benzaldehydes, resorcinol/α-naphthol/β-naphthol/4-hydroxycoumarin/3-methyl-4H-pyrazole-5(4H)-one, and malononitrile or ethyl cyanoacetate in the presence of a catalytic quantity of the aforementioned hybrid catalyst in EtOH/H₂O under reflux condition gave the corresponding highly functionalized 2-amino-4H-chromenes in satisfactory yields. The catalyst can be reused several times without appreciable loss in its catalytic activity.     

Molecular docking,linear and nonlinear QSAR studies on factor Xa inhibitors

Structural Chemistry - Factor Xa (FXa) enzyme has an important role in the blood coagulation system. Disruption in the enzyme function results in the production of blood clots. Therefore,...