New Dammarane‐Type Saponins from the Rhizomes of Panax japonicus

Phytochemical investigation of the rhizomes of Panax japonicus C. A. Meyer (Araliaceae) resulted in the isolation of two new dammarane‐type triterpenoid saponins, yesanchinoside R₁ ( 1 ) and yesanchinoside R₂ ( 2 ), together with one new natural product, 6′′′‐O‐acetylginsenoside Re ( 3 ). In addition, 25 known compounds, including 23 triterpenoid saponins, 4 – 26 , β‐sitosterol 3‐O‐β‐D ‐glucopyranoside ( 27 ), and ecdysterone ( 28 ), were also identified. The known saponins 12, 15 , and 18 – 22 were reported for the first time from the title plant. Their structures were elucidated on the basis of detailed spectroscopic analyses, including 1D‐ and 2D‐NMR techniques, as well as acidic hydrolysis.     

Facile synthesis of new imidazoles from direct reaction of 2,3‐diamino‐1,4‐naphthoquinone with aldehydes

New imidazoles were easily prepared from 2,3‐diamino‐1,4‐naphthoquinone and stoichiometric quantities of the appropriate aldehydes in dimethyl sulfoxide as a solvent. The reaction proceeded for few hours. The procedure can be generalized to different classes of aldehydes. 2‐Methyl‐1H‐naphtho[2,3‐d]imidazole‐4,9‐dione was also obtained in good yield during refluxing of 2,3‐diaminonaphthoquinone in acetic acid. The structure of the newly synthesized imidazoles was extensively investigated using NMR experiments. J. Heterocyclic Chem., (2011).     

Synthesis and properties of oligonucleotides that contain a triazole‐linked nucleic acid dimer

New chemically modified oligonucleotides at the site of the backbone are needed to improve the properties of oligonucleotides. A practical synthesis for a triazole‐linked nucleoside dimer based on a PNA‐like structure has been developed. This involves synthesizing two uracil‐based monomers that contain either an azide or an alkyne functionality, followed by copper‐catalyzed 1,3‐dipolar cycloaddition. This dimer was incorporated within an oligonucleotide via phosphoramidite chemistry and UV‐monitored thermal denaturation data illustrates slight destabilization relative to its target complementary sequence. This chemically modified dimer will allow for a future investigation of its properties within DNA and RNA‐based applications. J. Heterocyclic Chem., (2011).     

Development of a Biomimetic Enzyme‐linked Immunosorbent Assay Method for the Determination of Methimazole in Urine Sample

A fast and direct competitive biomimetic enzyme‐linked immunosorbent assay (BELISA) method was developed for the determination of methimazole (MMZ) in urine sample based on a molecularly imprinted film as an artificial antibody. This is the first example to monitor methimazole with a direct competitive biomimetic enzyme‐linked immunosorbent assay (BELISA) method. The imprinted film was directly synthesized on the well surface of MaxiSorp polystyrene 96‐well plate and characterized. The results showed that it exhibited an antibody‐like binding ability, rapid adsorption speed, high stability, which was particularly advantageous and suitable for BELISA development. The BELISA method established in this paper had a higher selectivity for MMZ than for the structurally related compounds and the IC₅₀ (calculated as the concentration giving 50% inhibition of color development) and the detection limit values under optimized experimental conditions were 70 ± 4 μg L^‐1 and 0.9 ± 0.04 μg L^‐1, respectively. The method was applied to the determination of MMZ in spiked urine sample with excellent recoveries ranging from 90% to 95%, and the imprinted film was able to be reused for 20 times without loss of sensitivity. The results obtained by BELISA correlated well with that obtained by the high performance liquid chromatography (HPLC) method.     

Electrochemical Detection of Catechol on Boron‐doped Diamond Electrode Modified with Au/TiO2 Nanorod Composite

Au/TiO₂ nanorod composites with different ratios of [TiO₂]:[Au] have been prepared by chemically reducing AuCl₄^‐ on the positively charged TiO₂ nanorods surface and used to modify boron‐doped diamond (BDD) electrodes. The electrochemical behaviors of catechol on the bare and different Au/TiO₂ nanorod composites‐modified BDD electrodes are studied. The cyclic voltammetric results indicate that these different Au/TiO₂ nanorod composites‐modified BDD electrodes can enhance the electrocatalytic activity toward catechol detection, as compared with the bare BDD electrode. Among these different conditions, the Au/TiO₂‐BDD3 electrode (the ratio of [TiO₂]:[Au] is 27:1) is the most choice for catechol detection. The electrochemical response dependences of the Au/TiO₂‐BDD3 electrode on pH of solution and the applied potential are studied. The detection limit of catechol is found to be about 1.4 × 10^‐6 M in a linear range from 5 × 10^‐6 M to 200 × 10^‐6 M on the Au/TiO₂‐BDD3 electrode.     

A facile and efficient addition reaction of nitrogen‐containing heterocyclic compounds with DMAD under neat conditions

A simple and efficient method was developed for the reaction of dimethyl acetylenedicarboxylate with benzothiazole, isoquinoline, quinoline, 3‐bromopyridine, pyridine, benzoxazole, benzimidazole, and 5,6‐dimethyl benzimidazole for the high‐yield synthesis of the related heterocyclic products ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ) in very short reaction time under neat procedure. The reaction of isoquinoline, 3‐bromopyridine, and pyridine afforded to diastereomeric mixtures of products 2 , 4 , and 5 , respectively. However, only one isomer of products 1 , 3 , 6 , 7 , and 8 were identified from the reaction of benzothiazole, quinoline, benzoxazole, benzimidazole, and 5,6‐dimethyl benzimidazole, respectively. Benzotriazole afforded to product 9 under these conditions. For comparison, the reactions were examined in different reaction mediums and/or under microwave irradiation. J. Heterocyclic Chem., (2011).     

Applying magnetic soft mold imprint technology with ultraviolet light‐emitting‐diode array on the fabrication of microlens arrays

This study proposed a novel technology, which uses exposed technology with ultraviolet light‐emitting‐diode (UV‐LED) arrays and the polydimethylsiloxane (PDMS) magnetic flexible soft mold imprint technology, to develop exposed equipments with UV‐LED arrays. This study used magnetic soft mold imprint technology to replicate the structure of microlens, providing a more effective alternative for imprint technology and application. The measurement results showed that PDMS with magnetic iron powder can precisely cast mold to replicate the structures of microlens. Electromagnetic plates were used to control even imprinting with magnetic force, in order to fill the mold of micro‐structure of the photo‐resist. Magnetic iron powder was added to PDMS to produce composite material, which can effectively avoid the transformation of pure PDMS during soft mold imprinting, and increase mechanical strength. Magnetic PDMS soft mold is easy to make, and the casting time is short, so that costs can be effectively reduced. Also with advantages of less free energy on its surface, and unlikely to adhere to the photo‐resist during imprinting, it can be combined with electromagnetic plates evenly to control the magnetic soft mold. This imprinting technology is a big advantage to the production process of micro‐structures during imprinting. Copyright © 2009 John Wiley & Sons, Ltd.     

Production of highly conductive textile viscose yarns by chemical vapor deposition technique: a route to continuous process

An oxidative chemical vapor deposition (OCVD) process was used to coat flexible textile fiber (viscose) with highly conductive polymer, poly (3,4‐ethylenedioxythiophene) (PEDOT) in presence of ferric (III) chloride (FeCl₃) oxidant. OCVD is a solvent free process used to get uniform, thin, and highly conductive polymer layer on different substrates. In this paper, PEDOT coated viscose fibers, prepared under specific conditions, exhibited high conductivity 14.2 S/cm. The effects of polymerization conditions, such as polymerization time, oxidant concentration, dipping time of viscose fiber in oxidant solution, and drying time of oxidant treated viscose fiber, were carefully investigated. Scanning electron microscopy (SEM) and FT‐IR analysis revealed that polymerization of PEDOT on surface of viscose fiber has been taken place and structural analysis showed strong interactions between PEDOT and viscose fiber. Thermogravimetric analysis (TGA) was employed to investigate the amount of PEDOT in PEDOT coated viscose fiber and interaction of PEDOT with viscose fiber. The effect of PEDOT coating on the mechanical properties of the viscose fiber was evaluated by tensile strength testing of the coated fibers. The obtained PEDOT coated viscose fiber having high conductivity, could be used in smart clothing for medical and military applications, heat generation, and solar cell demonstrators. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,characterization, and ethylene (Co)polymerization behavior of trichlorotitanium 2‐(1‐(arylimino)propyl)quinolin‐8‐olates

A series of trichlorotitanium complexes containing 2‐(1‐(arylimino)propyl)quinolin‐8‐olates was synthesized by stoichiometric reaction of titanium tetrachloride with the corresponding potassium 2‐(1‐(arylimino)propyl)quinolin‐8‐olates and was fully characterized by elemental analysis, nuclear magnetic resonance spectroscopy, and by single‐crystal X‐ray diffraction study of representative complexes. All titanium complexes, when activated with methylaluminoxane, exhibited high catalytic activity toward ethylene polymerization [up to 1.15 × 10⁶ g mol^?1(Ti) h^?1] and ethylene/α‐olefin copolymerization [up to 1.54 × 10⁶ g mol^?1 (Ti) h^?1]. The incorporation of comonomer was confirmed to amount up to 2.82 mol % of 1‐hexene or 1.94 mol % of 1‐octene, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011