ELECTROANALYSIS, Issue 4 2007
Guo-Song Lai
Abstract A sensitive and selective electrochemical method for the determination of dopamine (DA) was developed using a calix[4]arene crown-4 ether (CACE) film modified glassy carbon electrode (GCE). The modified electrode exhibited good electrocatalytic activity for electrochemical oxidation of DA in the pH,6.00 Britton,Robinson buffer solution, and ascorbic acid (AA) did not interfere with it. The diffusion coefficient (D=2.7×10,5,cm2 s,1), and the kinetic parameter such as the electron transfer coefficient (,=0.54) of DA at the surface of CACE were determined using electrochemical approaches. The catalytic oxidation peak currents showed a linear dependence on the DA concentration and a linear analytical curve was obtained in the range of 2.0×10,5,1.0×10,3,M of DA with a correlation coefficient of 0.9990. The detection limit (S/N=3) was estimated to be 3.4×10,6,M. This method was also examined for the determination of DA in an injection sample. In addition, effects of possible interferences were investigated. The present work shows the potential of the proposed method for the fabrication of a modified electrode, as it can be effectively used for voltammetric detection of DA. [source]

Ether: a forgotten addiction

ADDICTION, Issue 8 2003
Sonia Krenz
ABSTRACT Among abused inhalants, ether has recently received little attention. The case of a patient suffering from ether dependence is reported. Whereas several features of DSM-IV dependence were fulfilled, no physical withdrawal signs were observed. [source]

Postnatal handling alters the activation of stress-related neuronal circuitries

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2000
István M. Ábrahám
Abstract Postnatal handling, as a crucial early life experience, plays an essential role in the development of hypothalamo-pituitary,adrenal axis responses to stress. The impact of postnatal handling on the reactivity of stress-related neuronal circuitries was investigated in animals that were handled for the first 21 days of life and as adults they were exposed to physical (ether) or emotional (restraint) challenge. To assess neuronal activation we relied on the induction of immediate-early gene product c-Fos and analysed its spatial and temporal distribution at various time intervals after stress. Ether and restraint commonly activated parvocellular neurons in the hypothalamic paraventricular nucleus, and resulted in activation of brain areas providing stress-related information to the hypothalamic effector neurons and/or in regions governing autonomic and behavioural responses to stress. Beyond these areas, the strength and timing of c-Fos induction showed stressor specificity in olfactory and septal region, basal ganglia, hypothalamus, hippocampal formation, amygdala and brainstem. Handled rats displayed a lower number of c-Fos-positive cell nuclei and weaker staining intensity than non-handled controls in the hypothalamic paraventricular nucleus, bed nucleus of stria terminalis, central nucleus of amygdala, hippocampus, piriform cortex and posterior division of the cingulum. Significant differences were revealed in timing of c-Fos induction as a function of stressor and early life experience. Together, these data provide functional anatomical evidence that environmental enrichment in the early postnatal period attenuates the reactivity of stress-related neuronal circuitries in the adult rat brain. [source]

Improved and Controlled Complexation of Paraquat Derivatives by the Formation of a Bis(m -phenylene)-26-Crown-8-Based Lariat Ether

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2010
Mingming Zhang
Abstract A novel bis(m -phenylene)-26-crown-8-based lariat ether (i.e., 3b) was synthesized and characterized. It can bind paraquat derivatives more strongly than bis(m -phenylene)-26-crown-8 in solution. It forms pseudorotaxanes with two paraquat derivatives in the solid state. N -Methyl substitution was found to play an important role on the binding strength of lariat ether 3b. Furthermore, due to the introduction of two benzyloxy groups, its binding to paraquat derivatives can be switched off (and back on) by adding K+ (and then dibenzo-18-crown-6), and the disassociation percentage depends on the concentration of the added K+ ions. [source]

Flexible Route to Palmarumycin CP1 and CP2 and CJ-12.371 Methyl Ether

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2010
Karsten Krohn
Abstract The total synthesis of palmarumycin CP1 (4) and CP2 (5) and racemic CJ-12.371 methyl ether (17) is described using the Diels,Alder reaction of benzoquinone 1,8-dihydroxynaphthalene acetal (10) with 1-methoxy-1,3-butadiene under neat reaction conditions. The stereochemistry of adduct 15 was confirmed by single-crystal X-ray analysis. The transformation of 15 into target products 4, 5, and 17 involved dehydrogenation, methyl ether cleavage, and reduction and oxidation steps. [source]

Direct Synthesis of Protected Arylacetaldehydes by Tetrakis(phosphane)palladium-Catalyzed Arylation of Ethyleneglycol Vinyl Ether

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2006
Isabelle Kondolff
Abstract A range of aryl bromides undergo Heck reaction with ethylene glycol vinyl ether, in the presence of [PdCl(C3H5)]2/cis,cis,cis -1,2,3,4-tetrakis[(diphenylphosphanyl)methyl]cyclopentane as catalyst, to give regioselectively protected arylacetaldehydes in good yields. The ,-arylation products were obtained in with 93,100,% selectivity with electron-poor aryl bromides or heteroaryl bromides. Furthermore, this catalyst can be used at low loading, even for reactions with sterically hindered aryl bromides. The aryl vinyl ether intermediates undergo subsequent ketalisation to give the corresponding 2-benzyl-1,3-dioxolane derivatives.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

Odoriferous Cyclic Ethers via Co-Halogenation Reaction: Facile Preparation of Nerol Oxide, Florol®, Florol® Methyl Ether, and Pityol® Methyl Ether

HELVETICA CHIMICA ACTA, Issue 1 2007
Pankaj Gupta
Abstract A series of odoriferous cyclic ethers, including nerol oxide (1), Florol® (2), Florol methyl ether (3), and Pityol® methyl ether (4b), were prepared by a versatile synthetic protocol based on co-halogenation with 1,3-dibromo-5,5-dimethylhydantoin (=,1,3-dibromo-5,5-dimethylimidazolidine-2,4-dione; DDH) as the key step. The methodology provides a facile access to important perfumery molecules from abundantly available monoterpene alcohols. [source]

Solvatochromic Analysis of Partition Coefficients in the o -Nitrophenyl Octyl Ether (o -NPOE)/Water System

HELVETICA CHIMICA ACTA, Issue 11 2003
Xiangli Liu
The objective of this study was to unravel the structural properties responsible for the partitioning of solutes in o -nitrophenyl octyl ether (o -NPOE)/H2O, a new solvent system for the determination of the partition coefficients of ions. A set of 88 compounds (including drugs) was selected to allow a regular and broad distribution of property spaces. Partition coefficients in o -NPOE/H2O (log,Pnpoe) were measured by the shake-flask or the potentiometric method. Linear solvation free-energy relationship (LSER) analyses showed that Van der Waals volume, H-bond-acceptor basicity, and H-bond-donor acidity are the three molecular descriptors of solutes determining their log,Pnpoe values. The partitioning mechanism of the investigated compounds in o -NPOE/H2O is controlled by the same structural properties as it is in 1,2-dichloroethane (DCE)/H2O. ,log,Poct,npoe Values (difference between log,Poct and log,Pnpoe) express mainly dipolarity/polarizability and H-bond-donor acidity. The solvent o -NPOE is shown to be a good candidate to replace DCE in measurements of lipophilicity. [source]

4-Aminothiourea Prolinol tert -Butyldiphenylsilyl Ether: A Chiral Secondary Amine-Thiourea as Organocatalyst for Enantioselective anti -Mannich Reactions

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009
Hui Zhang
Abstract anti -Selective Mannich reactions of N - p -methoxyphenyl (PMP)-protected ,-iminoglyoxylate with unmodified aldehydes or ketones were effectively catalyzed by 4-aminothiourea prolinol tert -butyldiphenylsilyl ether. The reactions led to chiral ,-amino carbonyl compounds in high yields (up to 94%), excellent diastereo- and enantioselectivities (up to 98% de and >99% ee). The study demonstrated for the first time that direct Mannich-type reactions of unmodified aldehydes or ketones to ,-iminoglyoxylate can be promoted by secondary amine-thiourea chiral organocatalyst. [source]

Sulfobutyl Ether-,-Cyclodextrins: Promising Supramolecular Carriers for Aqueous Organometallic Catalysis

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2005
Philippe Blach
Abstract The potentialities of sulfobutyl ether-,-CDs derivatives as supramolecular carrier in a biphasic Tsuji,Trost reaction catalyzed by a water-soluble palladium complex of trisulfonated triphenylphosphine have been investigated. The efficiency of these cyclodextrins (CDs) strongly depends on the average molar substitution degree of cyclodextrin and the highest rate enhancements were obtained with cyclodextrins containing about 7 sulfobutyl ether groups. This result was attributed to the absence of a strong interaction between this cyclodextrin and the trisulfonated triphenylphosphine used to dissolve the catalyst in the aqueous phase and to the presence of an extended hydrophobic cavity allowing a better molecular recognition between the substrate and the cyclodextrin. This constitutes the first example of a non-interacting ,-cyclodextrin/phosphine couple with high catalytic activities. [source]

Functions of erg K+ channels in excitable cells

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 1 2004
Jürgen R. Schwarz
Abstract Ether-à-go-go -related gene (erg) channels are voltage-dependent K+ channels mediating inward-rectifying K+ currents because of their peculiar gating kinetics. These characteristics are essential for repolarization of the cardiac action potential. Inherited and acquired malfunctioning of erg channels may lead to the long QT-syndrome. However, erg currents have also been recorded in many other excitable cells, like smooth muscle fibres of the gastrointestinal tract, neuroblastoma cells or neuroendocrine cells. In these cells erg currents contribute to the maintenance of the resting potential. Changes in the resting potential are related to cell-specific functions like increase in hormone secretion, frequency adaptation or increase in contractility. [source]

Improvement of Subcutaneous Bioavailability of Insulin by Sulphobutyl Ether ,-Cyclodextrin in Rats

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 8 2000
KEIICHI TOKIHIRO
The objective of this study was to examine and compare how hydrophilic ,-cyclodextrin derivatives (,-CyDs) improve the bioavailability of insulin following subcutaneous injection of insulin solution in rats. When insulin solutions in the absence of ,-CyDs were injected into the dorsal subcutaneous tissues of rats, the absolute bioavailability of insulin calculated from plasma immunoreactive insulin (IRI) levels was approximately 50%. When maltosyl-,-cyclodextrin was added to the solutions, there was no change in the plasma IRI levels and hypoglycaemia compared with those of the insulin-alone solution. Dimethyl-,-cyclodextrin decreased the bioavailability of insulin, although it increased the maximal concentration of IRI in plasma and the capillary permeability of the fluorescein isothiocyanatedextran 40, a non-degraded permeation marker. When insulin solutions containing sulphobutyl ether-,-cyclodextrin with a degree of substitution of the sulphobutyl group of 3,9 (SBE4-,-CyD) were injected, the IRI level rapidly increased and maintained higher IRI levels for at least 8h. The bioavailability of the insulin/SBE4-,-CyD system was about twice that of insulin alone and approached 96%. The enhancing effects of SBE4-,-CyD may be in part due to the inhibitory effects of SBE4-,-CyDs on the enzymatic degradation and/or the adsorption of insulin onto the subcutaneous tissue at the injection site, although this does not apparently facilitate capillary permeability. These results suggest that SBE4-,-CyD in aqueous insulin injection for subcutaneous administration is useful for improving the bioavailability and the hence the pharmacological effects of insulin. [source]

Capillary gas-chromatographic determination of spermidine in hair lotion

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2006
Veniero Gambaro
Abstract Biogenic polyamines, such as spermidine (SPD, NH2,(CH2)4,NH,(CH2)3,NH2), are ubiquitous polycationic molecules which play a definitive role in many biological processes such as nucleic acid metabolism, protein synthesis, and cell growth. SPD is commonly used as an ingredient in hair lotions, because it seems to promote hair growth. This work describes a capillary GC method for quantitative determination of SPD in hair lotions using 1,6-diaminohexane as internal standard, a methyl silicone capillary column, and a flame ionisation detector. Aliquots of hair lotion were treated with an alkaline aqueous solution and internal standard was added. The emulsion was extracted with diethyl ether containing ethyl chloroformate. Ether extracts, evaporated to dryness and reconstituted in ethyl acetate, were analysed by capillary GC with flame ionisation detection. Validation took into account the specificity, linearity, precision, and accuracy of the analytical method: these parameters were valid for the quantitative determination of SPD in hair lotion. [source]

Copolymerization of Ethylene with 2,7-Octadienyl Methyl Ether in the Presence of Metallocene and Nickel Diimine Catalysts

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2009
Mércia Fernandes
Abstract In this work, copolymers of ethylene with 2,7-octadienyl methyl ether have been synthesized in the presence of three single-site catalysts. The obtained copolymers not only have a polar ether function but also a double bond in the side chains that is useful for secondary reactions. The polymers were characterized by GPC, EA, DSC, NMR, and FT-IR. The catalytic activity depends on the kind of catalysts, the concentration of the polar monomer, and the concentration of the protecting agent. Up to 7.3 wt.-% of MODE could be incorporated by the metallocene catalyst. These are in average 120 functional side groups in a polymer molecule with a molecular mass of 230,000. [source]

Microwave-Accelerated Polymerization of 2-Phenoxymethyl-1,4,6-trioxaspiro[4,4]nonane with Diglycidyl Ether of Bisphenol A

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2007
Judit Canadell
Abstract The cationic copolymerization of 2-phenoxymethyl-1,4,6-trioxaspiro[4,4]nonane with DGEBA under microwave irradiation using ytterbium and lanthanum triflates as initiators is described. A comparison with thermal heating showed a great enhancement in the reaction rates and a higher SOE incorporation in the network. The double ring opening of SOE reduces the usual shrinkage of epoxy resins on curing, and it was lower under microwave irradiation. Moreover, the ytterbium triflate initiator lead to a higher incorporation of linear ester moieties in the network than lanthanum triflate. [source]

Tartaric Acid Starch Ether: A Novel Biopolymer-Based Polyelectrolyte

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2003
Carsten Grote
Abstract New tartaric acid starch ethers have been synthesized applying starch sources of different amylose content. The reactions were carried out heterogeneously in ethanol/water mixtures with cis -disodiumepoxysuccinate as etherifying reagent leading to products of a degree of substitution (DS) up to 0.3. The molecular structure of the new starch ethers was evaluated by elemental analysis, FTIR and 13C NMR spectroscopy. Preliminary studies using a convenient titration method indicate a high binding capacity for Ca2+ ions which is dependent on the starch source and DS. Tartaric acid starch ethers. [source]

Photochemical Addition of Ethers to C60: Synthesis of the Simplest [60]Fullerene/Crown Ether Conjugates,

ANGEWANDTE CHEMIE, Issue 34 2010
Manolis
Einfache [60]Fulleren-Krönung: Die einfachsten und bislang unzugänglichen C60 -Kronenether-Konjugate wurden effektiv über freie Radikale hergestellt, wobei die sonst unreaktive , -C-H-Bindung einer Reihe strukturell unterschiedlicher Mono- oder Polyether und -sulfide aktiviert wurde. Diese einfache Methode macht eine neuartige, auf Fulleren basierende Materialklasse schnell zugänglich. [source]

Selective and Flexible Transformation of Biomass-Derived Platform Chemicals by a Multifunctional Catalytic System,

ANGEWANDTE CHEMIE, Issue 32 2010
Frank
Eine nachhaltige Versorgungskette: Die kontrollierte Überführung der aus Biomasse erhaltenen Plattformverbindungen Lävulinsäure (LA) und Itaconsäure (IA) in die entsprechenden Lactone, Diole oder cyclischen Ether (siehe Bild) wird durch einen multifunktionellen molekularen Katalysator möglich. [source]

Straightforward Synthesis of Ethers: Metal-Free Reductive Coupling of Tosylhydrazones with Alcohols or Phenols,

ANGEWANDTE CHEMIE, Issue 29 2010
José Barluenga Prof.
Einfach zum Ether: Erhitzen von Lösungen, die ein Tosylhydrazon und ein Phenol oder einen anderen Alkohol enthalten, in Gegenwart von K2CO3 ergibt die entsprechenden Arylalkyl- und Alkylalkylether (siehe Schema; MW=Mikrowellen, Ts=Tosyl). Die Reaktion kommt als neue Methode für die reduktive Veretherung von Carbonylverbindungen in Betracht. [source]

Titelbild: Verbrennungschemie der Biokraftstoffe: von Ethanol bis Biodiesel (Angew. Chem.

ANGEWANDTE CHEMIE, Issue 21 2010
21/2010)
Biodiesel ein Gemisch von Estern, wird aus Raps produziert; weitere potenzielle Biokraftstoffe sind Alkohole und Ether. Wie K. Kohse-Höinghaus et,al. im Aufsatz auf S.,3652,ff. schildern, besteht bei Kraftstoffmolekülen ein signifikanter Einfluss der Struktur auf die Verbrennungschemie. Die komplexen chemischen Reaktionswege der Brennstoffzersetzung und -oxidation können durch Massenspektrometrie und Lasertechniken direkt analysiert werden. [source]

Synthesis of Phenol, Aromatic Ether, and Benzofuran Derivatives by Copper-Catalyzed Hydroxylation of Aryl Halides,

ANGEWANDTE CHEMIE, Issue 46 2009
Dongbing Zhao
Gruppentausch: Die kupferkatalysierte Synthese von Phenolen aus Arylhalogeniden gelang unter relativ milden Reaktionsbedingungen. Alkylarylether und Benzofurane ließen sich glatt durch Eintopf-Dominoreaktionen herstellen, die auf einer Hydroxylierung von Aryliodiden beruhten (siehe Schema). [source]

Production of Hydrogen from Dimethyl Ether over Supported Rhodium Catalysts

CHEMCATCHEM, Issue 2 2009
Gyula Halasi
Abstract Infrared (IR) spectroscopy revealed that dimethyl ether (DME) undergoes partial dissociation on pure and rhodium-containing CeO2 at 300,K to yield methoxy and methyl species. This process is promoted by the presence of rhodium. By means of thermal desorption measurements (TPD), the adsorption of DME on Rh/CeO2 at 300,K and subsequent decomposition of DME (Tp,370,K), releasing H2, CO, CO2, and CH4, with Tp between 420 and 673,K, were ascertained. Rh/CeO2 is an effective catalyst for the decomposition of DME to give H2 (29,35,%), CO (27,30,%) and CH4 (32,38,%) as major products with complete conversion at 673,723,K. Adding water to DME changed the product distribution and increased the selectivity of H2 formation from 30,35,% to 58,% at 723,K. In,situ IR spectroscopy showed absorption bands of CO at 2034 and 1893,cm,1 during the reaction at 673,773,K. Deactivation of the catalyst did not occur at 773,K during the time measured (approximately 10 h). Rh deposited on carbon Norit also exhibited a high activity towards the decomposition of DME, but the selectivity towards hydrogen was lower. [source]

ChemInform Abstract: The Reaction of 1-Silylcyclopropyl Anions with Dichloromethyl Methyl Ether: The Efficient Synthesis of Cyclopropyl Silyl Ketones via Cyclopropylidene Derivatives.

CHEMINFORM, Issue 23 2010
Toshiaki Nishizawa
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Enantioselective Friedel,Crafts Alkylation of Indoles with Aromatic ,,,-Unsaturated Aldehydes Catalyzed by Diphenylprolinol Silyl Ether.

CHEMINFORM, Issue 16 2010
Zhi-Jing Wang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: NbCl5 -Mediated Deprotection of Methoxy Methyl Ether.

CHEMINFORM, Issue 44 2009
J. S. Yadav
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Highly Enantioselective Michael Addition Reactions in Water Catalyzed by an Insoluble MPS-Supported 4-Sulfonamidyl Prolinol tert-Butyldiphenylsilyl Ether.

CHEMINFORM, Issue 39 2009
Yongming Chuan
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Preparation of 1,1,-Oxy-bis(3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole) and 2-(N-(p-Toluenesulfonyl)imino)iodobenzylmethyl Ether.

CHEMINFORM, Issue 33 2009
Alexander J. Blake
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Regio- and Enantioselective Direct Oxyamination Reaction of Aldehydes Catalyzed by ,,,-Diphenylprolinol Trimethylsilyl Ether.

CHEMINFORM, Issue 7 2008
Claudio Palomo
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Prolinol tert-Butyldiphenylsilyl Ether as Organocatalyst for the Asymmetric Michael Addition of Cyclohexanone to Nitroolefins.

CHEMINFORM, Issue 5 2008
Fengying Liu
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Two-Step Formal [3 + 2] Cycloaddition of Enones/Enals and Allenyl MOM Ether: Gold-Catalyzed Highly Diastereoselective Synthesis of Cyclopentanone Enol Ether Containing an All-Carbon Quaternary Center.

CHEMINFORM, Issue 39 2007
Xiaogen Huang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]