Time Dependent Magnetohydrodynamic Flow of CuO/Al2O3/TiO2 Water Based Nanofluid along a Vertical Permeable Stretching Surface

Colloid Journal - Time dependent magnetohydrodynamic flow of viscous incompressible CuO/Al2O3/TiO2 water based nanofluid along a vertical permeable stretching surface in the presence of external...     

TLC densitometric quantification of picrosides (picroside-I and picroside-II) in Picrorhiza kurroa and its substitute Picrorhiza scrophulariiflora and their antioxidant studies

Picroside‐I and picroside‐II are known bioactive metabolites in Picrorhiza species. In the present study a simple, precise method has been established for the simultaneous determination of picrosides (picroside‐I and picroside‐II) in two different Picrorhiza species, P. kurroa and P. scrophulariiflora. This method was also validated for accuracy, precision, robustness, limit of detection and quantification, repeatability and recovery, according to International Conference of Harmonization guidelines. Separation and quantification was achieved by HPTLC using as the mobile phase chloroform–methanol (88:12, v/v) on precoated silica gel 60F₂₅₄ aluminum plates. Densitometric determination was carried out at wavelength λ_max 254 nm in UV absorbance mode. Comparative study also revealed that picroside‐I and picroside‐II are higher in P. scrophulariiflora than P. kurroa. Picroside‐I content was found to be 1.258 and 1.611%, and picroside‐II was estimated as 0.481 and 0.613% in P. kurroa and P. scrophulariiflora, respectively. Antioxidant potential of these two Picrorhiza species was also studied using DPPH. At a concentration of 0.1 mg/mL the scavenging activities of P. kurroa and P. scrophulariiflora were found to 37.70 and 34.30%, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Diastereoselective construction of syn-α-oxyamines via three-component α-oxyaldehyde-dibenzylamine-alkyne coupling reaction: application in the synthesis of (+)-β-conhydrine and its analogues

A Cu(i)-catalyzed α-oxyaldehyde-dibenzylamine-alkyne coupling reaction was delineated for the construction of α-oxyamines with excellent yields and diastereoselectivity. Crystal structure analysis and theoretical calculations were also supportive of the formation of syn-α-oxyamines as the major products. Application of the methodology addresses the synthesis of (+)-β-conhydrine along with analogs having two different diversity features. A ring size variation allows construction of piperidine and pyrrolidine rings while a variation of side arm functionality is achieved by complete regioselective opening of epoxide by different organocopper ylides (Gilman reagents). A lactam-Cu(i) complexation motif is proposed which allows an intramolecular attack of ylides at the terminal epoxy carbon via the six-membered cyclic transition state. The present work features the synthesis of (+)-β-conhydrine over eight steps in 26% yield and its seven analogs in 21-28% yields.     

A reaction based chromofluorogenic turn-on probe for specific detection of fluoride over sulfide/thiols

A new reaction based probe fluorescein nosylate (R1) has been designed and synthesized for selective recognition of F⁻ in acetonitrile (CH₃CN) by exploiting both its nucleophilic and basic character. Probe R1 consists of fluorescein dye as a signalling unit while 4-nitrobenzenesulfonyl chloride as the masking unit. The F⁻ plays the role of de-masking agent to set free the fluorescein moiety in its open form from R1 leading to significant changes in its absorption/emission profile. The detection of F⁻ amidst of sulfide/thiols through receptors undergoing nucleophilic scission is a tedious job due to similarity in their extent of basicity/nucleophilicity. Here, we present a convenient solution for the same in the form of R1 which detects F⁻ selectively over sulfide/thiols in CH₃CN with a high detection limit of 4.6 × 10⁻⁷ M and 2.75 × 10⁻⁸ M determined through UV–visible and fluorescence titration data, respectively.     

Composition‐Tailored 2 D Mn1−xRuxO2 Nanosheets and Their Reassembled Nanocomposites: Improvement of Electrode Performance upon Ru Substitution

Composition‐tailored Mn_1?xRu_xO₂ 2 D nanosheets and their reassembled nanocomposites with mesoporous stacking structure are synthesized by a soft‐chemical exfoliation reaction and the subsequent reassembling of the exfoliated nanosheets with Li⁺ cations, respectively. The tailoring of the chemical compositions of the exfoliated Mn_1?xRu_xO₂ 2 D nanosheets and their lithiated nanocomposites can be achieved by adopting the Ru‐substituted layered manganese oxides as host materials for exfoliation reaction. Upon the exfoliation–reassembling process, the substituted ruthenium ions remain stabilized in the layered Mn_1?xRu_xO₂ lattice with mixed Ru³⁺/Ru⁴⁺ oxidation state. The reassembled Li–Mn_1?xRu_xO₂ nanocomposites show promising pseudocapacitance performance with large specific capacitances of approximately 330 F g^?1 for the second cycle and approximately 360 F g^?1 for the 500th cycle and excellent cyclability, which are superior to those of the unsubstituted Li–MnO₂ homologue and many other MnO₂‐based materials. Electrochemical impedance spectroscopy analysis provides strong evidence for the enhancement of the electrical conductivity of 2 D nanostructured manganese oxide upon Ru substitution, which is mainly responsible for the excellent electrode performance of Li–Mn_1?xRu_xO₂ nanocomposites. The results underscore the powerful role of the composition‐controllable metal oxide 2 D nanosheets as building blocks for exploring efficient electrode materials.     

Simultaneous Determination of Bergenin and Gallic Acid in Different Bergenia Species

JPC – Journal of Planar Chromatography – Modern TLC - A simple, highly precise method has been established for the simultaneous determination of the bioactive molecules bergenin and...     

Total synthesis of pachastrissamine (jaspine B) enantiomers from d-glucose

Synthesis of both enantiomers of pachastrissamine is described from a common chiral template. The stereoselective construction of the central tetrahydrofuran units was based on the pseudodesymmetrization of a pentodialdo-1,4-furanose derivative taking advantage of the latent symmetry present.