2-(N-Allylaminomethyl)cinnamaldehydes as substrates for syntheses of aza-polycycles via intramolecular cycloaddition reactions

Syntheses of a variety of aza-polycycles employing 2-(N-allylaminomethyl)cinnamaldehydes derived from Morita–Baylis–Hillman adducts of acrylates via intramolecular 1,3-dipolar cycloaddition, or Aza-Diels–Alder or domino Knoevenagel/hetero Diels–Alder cycloaddition reactions are described. Whereas the Aza-Diels–Alder afforded a mixture of cis- and trans-isomers of substituted 1,2,3,4,4a,5,10,10a-octahydrobenzo[b][1,6]naphthyridines, the 1,3-dipolar cycloaddition and domino Knoevenagel/hetero Diels–Alder were diastereoselective to produce exclusively cis-derivatives of 1,2,3,4,4a,6,7,8,9,9a-decahydro-1H-pyrido[3,4-b]pyrrolizine-8a-carboxylates and 3,4,4a,5,7,8,9,10b-octahydro-1H-chromeno[3,4-c]pyridin-10(2H)-ones, respectively.     

Synthesis of sterically hindered ketones from aldehydes via O-silyl oximes

A mild and efficient method to synthesize sterically hindered ketones from aldehydes via O-silyl oximes was developed. Treatment of O-triphenylsilylated oximes with alkyl iodides in the presence of triethyl borane afforded the corresponding ketones.     

Computational prediction of monosaccharide binding free energies to lectins with linear interaction energy models

The linear interaction energy (LIE) method to compute binding free energies is applied to lectin‐monosaccharide complexes. Here, we calculate the binding free energies of monosaccharides to the Ralstonia solanacearum lectin (RSL) and the Pseudomonas aeruginosa lectin‐II (PA‐IIL). The standard LIE model performs very well for RSL, whereas the PA‐IIL system, where ligand binding involves two calcium ions, presents a major challenge. To overcome this, we explore a new variant of the LIE model, where ligand–metal ion interactions are scaled separately. This model also predicts the saccharide binding preference of PA‐IIL on mutation of the receptor, which may be useful for protein engineering of lectins. © 2012 Wiley Periodicals, Inc.     

Ordered self-assembled locked nucleic acid (LNA) structures on gold(111) surface with enhanced single base mismatch recognition capability

Locked nucleic acid (LNA) is a conformationally restricted nucleic acid analogue, which is potentially a better alternative than DNA for application in the nucleic acid based biosensor technologies, due to its efficient and sequence-specific DNA/RNA detection capability and lack of molecule-surface interaction on solid surfaces, compared to DNA. We report, for the first time, a straightforward way (based on simple immersion method) of generating an ordered self-assembled LNA monolayer, which is bioactive, onto a gold(111) surface. This layer is capable of giving rise to a stronger DNA recognition signal (4-4.5 times) than its DNA counterpart, and importantly, it can differentiate between a fully complementary DNA target and that having a single base mismatch, where the mismatch discrimination ratio is almost two times compared to the ratio relevant in case of DNA-based detection. We have presented high-resolution atomic force microscopy (AFM) topographs of the well-defined one-dimensional LNA molecular ordering (few hundred nanometers long) and of the two-dimensional ordered assembly formed over a large area (7 μm × 7 μm) due to parallel positioning of the one-dimensional ordered arrangements. The effects of different parameters such as LNA concentration and incubation time on LNA self-assembly have been investigated. Further, reflection absorption infrared (RAIR) spectroscopy has been applied to obtain information about the orientation of the surface-immobilized LNA molecules for the first time. It has been found that the LNA molecules undergo an orientational transition from the "lying down" to the "upright" configuration in a time scale of few hours.     

Physicochemical investigations of microemulsification of coconut oil and water using polyoxyethylene 2-cetyl ether (Brij 52) and isopropanol or ethanol

The microemulsification of coconut oil/polyoxyethylene 2-cetyl ether/2-propanol or ethanol/water was investigated. The phase behaviors of the mixed system were examined. The shear viscosity at different temperatures was measured to derive activation parameters for the viscous flow. The diffusion coefficient of the microemulsions at different compositions was determined by the DLS method. The energetics of solubilization of water into oil + Brij + alkanol as well as of oil into water + Brij + alkanol forming w/o and o/w microemulsions, respectively, were calorimetrically determined.     

Theoretical studies on atmospheric chemistry of HFE‐347mcc3: reactions with OH radicals and Cl atoms

Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas phase reactions of CF₃CF₂CF₂OCH₃ (HFE‐347mcc3) with OH radicals and Cl atoms using M06‐2X/6‐31 + G(d,p) level of theory. Reaction profiles are modeled including the formation of pre‐reactive and post‐reactive complexes at entrance and exit channels, respectively. Using group‐balanced isodesmic reactions, the standard enthalpies of formation for species are also reported. The calculated bond dissociation energy for C―H bond is in good agreement with previous data. The rate constants of the two reactions are determined for the first time in a wide temperature range of 250–1000 K. At 298 K, the calculated rate coefficients are in good agreement with the experimental results. The atmospheric life time of HFE‐347mcc3 is estimated to be 4.4 years. Copyright © 2014 John Wiley & Sons, Ltd.     

Entropy stable shock capturing space–time discontinuous Galerkin schemes for systems of conservation laws

We present a streamline diffusion shock capturing spacetime discontinuous Galerkin (DG) method to approximate nonlinear systems of conservation laws in several space dimensions. The degrees of freedom are in terms of the entropy variables and the numerical flux functions are the entropy stable finite volume fluxes. We show entropy stability of the (formally) arbitrarily high order accurate method for a general system of conservation laws. Furthermore, we prove that the approximate solutions converge to the entropy measure valued solutions for nonlinear systems of conservation laws. Convergence to entropy solutions for scalar conservation laws and for linear symmetrizable systems is also shown. Numerical experiments are presented to illustrate the robustness of the proposed schemes.     

Low‐temperature Raman spectroscopic studies in NaNbO3

Raman spectroscopic measurements were carried out in the temperature range 10–300 K to understand the low‐temperature antiferroelectric (AFE)–ferroelectric (FE) phase transition in NaNbO₃. Several modes in the low wavenumber range were found to disappear, while some new modes appeared across the transition. The temperature dependence of mode wavenumbers suggests that, during cooling, the AFE–FE phase transition begins to occur at 180 K, while the reverse transition starts at 260 K during heating. During cooling, the two phases were found to coexist in the temperature range of 220–160 K. Upon heating, the FE phase is retained up to 240 K and both FE and AFE phases coexist in the temperature range 240–300 K. In contrast to the earlier reports, the present results suggest a different coexistence region and the reverse transition temperature. The reported relaxor‐type FE behaviour over a broad temperature is consistent with the observed coexistence of phases during cooling and heating cycles. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,characterization, and antifungal and antibacterial studies of nickel(II)thiodiamine complexes

Nickel(II) complexes of type [Ni(L)₂Cl₂] and [Ni(L)₂(OCOCH₃)₂], where L = (cyclohexyl-N-thio)-1,2-ethylenediamine (L¹) and (cyclohexyl-N-thio)-1,3-propanediamine (L²) has been synthesized and characterized by elemental analysis, FT-IR, mass, UV-Vis, and ¹H NMR spectroscopic studies. The thiodiamines coordinate as a bidentate N-S ligand. The ratio of the metal: ligand was 1: 2 for all the complexes. The binding sites are the azomethine nitrogen and thioamide sulfur. The complexes are found to be soluble in acetone, dimethylformamide, and dimethylsulfoxide. All the complexes were found amorphous in nature. Molar conductance values in DMSO indicate the nonelectrolyte nature of the complexes. In vitro antifungal and in vitro antibacterial studies were performed against fungal and bacterial strains, Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger, and Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, respectively. Preliminary antimicrobial screening shows the good results against both the fungal and the bacterial strains, which can lead through the investigation of better drug. The article is published in the original.