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  • 1
    ISSN: 1573-1561
    Keywords: Hepialus ; Lepidoptera ; Hepialidae ; swift moth ; pheromone ; dihydropyrone ; 2,9-dioxabicyclo[3.3.1] nonane ; behavior ; electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract (R)-6-Ethyl-2-methyl-2,3-dihydro-4H-pyran-4-one, (1R,3S,5R)-3-ethyl-1,8-dimethyl-2,9-dioxabicyclo[3.3. 1]non-7-ene, and (1R,3S,5R)-3-ethyl-1,8-dimethyl-2,9-dioxabicyclo[3.3.1]non-7-en-6-one represent the main components in the male pheromone of the swift moth,Hepialus hecta. The amounts of the three components were 40, 5, and 5 μg per male, respectively. Structure elucidation of the compounds was based on spectroscopic data as compared to synthetic reference samples. The absolute configurations were determined by gas chromatography on chiral stationary phases; optically active samples served as reference compounds. Electrophysiological and behavioral experiments with natural material and synthetic samples clearly showed the three heterocyclic compounds to act as pheromones. (E, E)-α-Farnesene represents the main component of the scent secretion of maleHepialus humuli.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 102 (1969), S. 3378-3390 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Der Mechanismus der Stickstoff-Fixierung und Reduktion zu Ammoniak mittels metall-organischer Katalysatoren wird untersucht. Es wird angenommen, daß ein Titan (0)-Komplex den Stickstoff bindet und reduziert. Die Systeme (C5H5)2TiCl2/Alkalimetall eignen sich besonders für die Untersuchungen des Reaktionsmechanismus. Neben Stickstoff-Fixierung wird auch eine Wasserstoffaufnahme des Katalysators beobachtet. Die im Verlauf der Stickstoff-Fixierung auftretenden Elektronenspinresonanzspektren geben Hinweise auf die Zwischenstufen der Reaktion.
    Additional Material: 6 Ill.
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  • 3
    ISSN: 0009-2940
    Keywords: Enantiomerization ; Dynamic complexation gas chromatography ; Homofuran ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By computer simulation of experimental interconversion profiles, obtained by complexation gas chromatography, rate constants of enantiomerization have been determined for homofuran between 95 and 130°C. Since enantiomerization proceeds at similar rates in the mobile and stationary phase, the rate constants obtained by an Arrhenius plot are in excellent agreement with values determined independently by polarimetry between 60 and 90°C. We thus demonstrate that dynamic chromatography can be an easy means for the rapid determination of enantiomerization (or isomerization) barriers of ca. 70-120 kJ mol-1 requiring only minute amounts of racemic sample.
    Additional Material: 2 Ill.
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  • 4
    ISSN: 0009-2940
    Keywords: Asymmetric catalysis ; Cycloadditions ; Lewis acids ; Polymers ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dimethylpolysiloxane chain is covalently bound to the monomeric Lewis acid catalyst (1R)-(+)-oxovanadium(1V) bis[3- heptafluorobutanoylcamphorate] [(+)-5a] at the C-10 position of the camphor moiety yielding the novel chiral polymeric (1S)-( +)-oxovanadium(1V) bis[3-heptafluorobutanoylcamphorate] -dimethylpolysiloxane [( +)-6a][1]. The Lewis acid promoted hetero Diels-Alder reaction of trans-l-methoxy-3-(trimethylsilyloxy)- 1,3-butadiene (1) and benzaldehyde (2) is studied in the presence of the enantiomerically pure monomeric (5a, 5b) and polymeric (6a, 6b) catalysts. The monomeric and polymeric catalysts of identical chirality[1] invoke opposite enantioselectivities toward the formation of 2-phenyl- 2,3-dihydro-4H-pyrone (4). This remarkable result is corroborated by numerous control experiments. Thus, it is demonstrated that the environment of the active site of the catalyst is changed when the complex is fixed to a polymeric chain. In contrast to 5 and 6, the monomeric 12 and polymeric 13 europium(III) tris[3-heptafluorobutanoylcamphorates] of identical chirality invoke the same enantioselectivity toward the formation of 4. The concept of polymer attachment is utilized to recover the catalyst from the reaction mixture by precipitation and to recycle it for subsequent catalytic runs.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 101 (1968), S. 1594-1600 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Protonenresonanzspektren von Fünfringchelaten der α-Diimine, des Glyoxal-bis-hydrazons und von Ferrolen weisen auf eine cyclische Delokalisierung der π-Elektronen hin.
    Additional Material: 2 Tab.
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  • 6
    ISSN: 1573-904X
    Keywords: anticonvulsant activity ; enantiomer-enantiomer interaction ; enantiomers of propylisopropyl acetamide ; microsomal epoxide hydrolase ; pharmacokinetics, teratogenicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to evaluate there existed stereoselective effects in the pharmacokinetics, anticonvulsant activity, microsomal epoxide hydrolase (mEH) inhibition, and teratogenicity of the two enantiomers of propylisopropyl acetamide (PID), a CNS-active chiral amide analogue of valproic acid. Methods. Racemic PID, as well as the individual enantiomers, were intravenously administered to six dogs in order to investigate the stereoselectivity in their pharmacokinetics. Anticonvulsant activity was evaluated in mice (ip) and rats (oral), mEH inhibition studies were performed in human liver microsomes, and teratogenicity was evaluated in an inbred susceptible mice strain. Results. Following intravenous administration to dogs of the individual enantiomers, (R)-PID had significantly lower clearance and longer half-life than (S)-PID, however, the volumes of distribution were similar. In contrast, following intravenous administration of racemic PID, both enantiomers had similar pharmacokinetic parameters. In rats (oral), (R)-PID had a significantly lower ED50 in the maximal electroshock seizure test than (S)-PID; 16 and 25 mg/kg, respectively. PID enantiomers were non-teratogenic and did not demonstrate stereoselective mEH inhibition. Conclusions. (R)-PID demonstrated better anticonvulsant activity, lower clearance and a longer half-life compared to (S)-PID. When racemic PID was administered, the clearance of (S)-PID was significantly reduced, reflecting an enantiomer-enantiomer interaction.
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  • 7
    ISSN: 0899-0042
    Keywords: 2,2′-diisopropylbiphenyl ; racemization and enantiomerization ; rotational energy barrier ; computer simulation ; dynamic chiral gas chromatography ; cyclodextrin stationary phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By computer simulation of experimental dynamic gas chromatographic elution profiles, the rotational energy barrier ΔG= of racemic 2,2′-diisopropylbiphenyl has been determined as 114.6-115.0 kJ/mol (75-100°C). These data are in good agreement with a value that was determined previously by measuring the racemization kinetics of an enriched sample. This indicates that there is no measurable catalytic or inhibitory effect of the stationary phase. © 1994 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 350-353 
    ISSN: 0899-0042
    Keywords: xenobiotics ; pollutants ; non-planar aromatics ; chirality ; atropisomerism ; ab initio calculations ; electron correlation ; density functional theory ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational barriers of overcrowded PCBs are predicted by ab initio methods including electron correlation, thus settling the controversy between theory and experiment. For 2,2′,3,3′,4,6′-hexachlorobiphenyl (PCB 132), an enantiomerization barrier of 185 kJ/mol is calculated by B3LYP/6-31G*, in excellent agreement with the experimental data. Chirality 9:350-353, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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  • 9
    ISSN: 0899-0042
    Keywords: atropisomeric polychlorinated biphenyls (PCBs) ; Chirasil-Dex ; rotational barrier ; stopped-flow multidimensional gas chromatographic technique ; on-line enantiomerization kinetics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rotational barriers ΔG
    Additional Material: 3 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 140-146 
    ISSN: 0899-0042
    Keywords: enantioselective chromatography ; chiral selectands ; chiral selectors ; peak coalescence ; enantiomer separation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six scenarios of peak coalescence are distinguished in enantioselective chromatography. Where appropriate, they are verified by an experiment. Chirality 10:140-146, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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