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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1215-1218 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal properties of two ferrocene derivatives, substituted by either one or two cholesteryloxycarbonyl units, were investigated. While the monosubstituted ferrocene derivative 1 was found to be non-mesomorphic, the disubstituted ferrocene derivative 2 exhibited a crystal smectic-B phase. This result shows that ferrocene-containing thermotropic liquid crystals, despite the bulkiness of the metallocene core, are not limited to disordered calamitic phases.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 729 (1969), S. 198-204 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Frog Venoms.Isolation and Structure of Pumiliotoxin CPumiliotoxin C, a base of the composition C13H25N, is isolated as the crystalline hydrochloride from the skin extracts of Dendrobates pumilio, a strikingly colored Panamanian frog. Complete X-ray analysis of this new venom by the so-called symbolic addition procedure establishes the structure as 2-n-propyl-5-methyl-cis-decahydroquinoline, a type of base, though related to coniine, is here reported for the first time as a natural product. The relative configurations of the four asymmetric centers are elucidated. In addition to this venom there are the congeners pumiliotoxins A and B, as well as further homologs and analogs which have also been isolated from the related frog Dendrobates auratus, and characterized by mass spectra.
    Notes: Aus dem Hautextrakt des in Panama vorkommenden, auffallend gefärbten Froschs Dendrobates pumilio läβt sich das gut kristallisierende Hydrochlorid einer Base Pumiliotoxin C der Formel C13H25N isolieren. Durch Röntgen-Strukturanalyse dieser Base nach dem „symbolischen Additionsverfahren“ (symbolic addition procedure) läβt sich zeigen, daβ es sich um einen zum ersten Mal in der Natur beobachteten, dem Coniin weitläufig verwandten Giftstofftyp handelt, nämlich um ein 2-n-Propyl-5-methyl-cis-decahydrochinolin, dessen vier asymmetrische Zentren in ihrer relativen stereochemischen Bezeichnung aufgeklärt werden. Neben Pumiliotoxin C leiten sich auf Grund der Massenspektren die Pumiliotoxine A und B sowie noch weitere aus dem verwandten Frosch Dendrobates auratus isolierte Basen von einem ähnlichen cis-Deca- oder Octahydrochinolin-System ab.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1976 (1976), S. 1577-1583 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of Pumiliotoxin Crac-Pumiliotoxin C (PTX-C, rac-1) is obtained in a four step stereoselective synthesis, starting from ethyl 4-methyl-2-(1-pyrrolidinyl)-l-cyclohexenecarboxylate (6) and 1-(2-bromoethyl)- butylamine hydrobromide (7), in 25 % yield. This method can easily be adapted to the syn- thesis of optically active PTX-C and of other pumiliotoxins.
    Notes: rac-Pumiliotoxin C (PTX-C, rac-1) wird in einer 4stufigen stereoselektiven Synthese, ausgehend von 4-Methyl-2-( l-pyrrolidinyl)-l-cyclohexencarbonsäure-äthylester (6) und 1-(2- Bromäthyl)butylamin-hydrobromid (7) in 25 proz. Ausbeute erhalten. Dieses Verfahren läßt sich leicht auf die Synthese von optisch aktivem PTX-C und weiteren Pumiliotoxinen übertragen.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Antibioticum X-5108 ist ein Naturprodukt mit neuartiger Struktur. Behandlung des Antibioticums mit Essigsäure führte zu einem kristallinen Abbauprodukt, das als 3(S)-Äthyl-3, 3a, 5(S), 6, 7, 7 a(R)-hexahydro-3a(R), 7(R)-dihydroxy-6, 6-dimethyl-5-[1(cis), 3(trans)-pentadienyl]-2H-furo[3, 2-b]pyran-2-on (5) identifiziert wurde.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eleven new triterpenes with the lanostene-type skeleton were isolated from the benzene extract of western white pine bark. Their structures were determined mainly on the basis of physical and spectral data.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A literature survey indicated that stereospecific non-reductive β-face methylation at C(10) of steroidal synthesis intermediate BCD-tricyclic 9-en-5-ones had never been effected. An attempt to define the factors controlling the β/α product ratio in such alkylations was made. The course of methylation is significantly affected by the temperature. In the best case, methylation of the sodium enolate of 17 β-t-butoxy-19-(3,5-dimethyl-4-isoxazolyl)-deA-androst-9-en-5-one (18) in tetrahydrofuran at - 78° gave a β/α product ratio of 〉 5:1. The reaction mixture contained no unalkylated or dialkylated materials, indicating that enolate exchange probably did not occur at this temperature. The 10β-methylated product 23, isolated in 78% yield, was converted to Δ9(ll)-dehydrotestosterone (29). Compounds 23 and 29 are potential intermediates for the synthesis of 11-oxygenated steroids.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 59 (1976), S. 290-306 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of trimethyl-hydroquinone with methyl vinyl ketone in acidic methanol gave rac.-2-methoxy-2,5,7,8-tetramethyl-chroman-6-ol (8). This acetal was converted in four steps to rac.-(6-hydroxy-2,5,7,8-tetramethyl-chroman-2-yl)acetic acid (13). Acid 13 was readily resolved with α-methyl-benzylamine to give the (S)-enantiomer 14. Treatment of the unwanted (2 R)-isomer with acid regenerated 13, thus leading to an efficient use of this compound. Employing a side chain derived from phytol, 14 was converted to (2R, 4′R, 8′R)-α-tocopherol (1d, ‘natural’ vitamin E). A reaction sequence from 14 involving two highly stereoselective Claisen rearrangements has provided the first total synthesis of (2R,'E,7′E)-α-tocotrienol (2d).
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As an extension of previous studies on the total synthesis of (2R,4′R,8′R)-α-tocopherol (1) [1] [2], (S)-(-)-2-(6-benzyloxy-2,5,7,8-tetramethylchroman)acetic acid (6), a pivotal intermediate, possessing the absolute configuration required for construction of 1 was prepared by optical resolution of the racemic modification 11. the latter substance was obtained by two routes, one emanating from the hydroxy acetal 7 [1] and the other based upon the Lewis acid mediated cycloaddition of trimethylhydroquinone to rac.-3-hydroxy-3-methylpent-4-en-l-yl acetate (16) giving rac. ethyl 2-(6-hydroxy-2,5,7,8-tetramethyl-chroman)acetate (12).
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrathiafulvalenes. XIX. Synthesis and Properties of Electron Conducting Poly-Dithiolene Complexes with Ethylene Tetrathiolat and Tetrathiafulvalene Tetrathiolat as Bridge Ligands[1,3]-Dithiolo[4,5-d]-1,3-dithiol-2,5-dione 7 and 5-(5-oxo[1,3]-dithiolo[4,5-d]1,3-dithiole-2-ylidene)[1,3]-dithiolo[4,5-d]1,3-dithiol-2-one 8 were synthesised from 1,3-dithiole-2-thione-4,5-dithiolat. The ligands react with salts of iron, cobalt, nickel, palladium, platinum and copper to give the polymer complexes 22a-g and 23a-e, respectively. Irradiation of 7 in the presence of iron penta-, dicobalt octa- or nickel tetracarbonyl gives the corresponding dithiolene complexes 21a-c.The amorphous insoluble polymer complexes from types 21, 22, and 23 have been characterised by i.r.-spectroscopy, susceptibility and conductivity measurements.The nickel complexes have the highest electrical conductivity (σRT ∼ 10-1Ω-1cm-1, pellets) with a very low activation energy (0,045 eV, 100-300 K)A high electron delocalization in the direction of the polymer chain and an easy charge transfer from chain to chain is supposed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 19 (1963), S. 135-137 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Es wurde das System Natriumnitrit-Phosphoroxychlorid untersucht, um die neben Nitrosylchlorid entstehenden Reaktionsprodukte zu bestimmen. Dabei konnte entgegen früherer Darstellung kein NO gefunden werden. Die Reaktionsprodukte, die mittels gravimetrischer Analyse, stöchiometrischer Berechnung, der Destillation der gasförmigen Produkte und der röntgenographischen Untersuchung des festen Rückstandes bestimmt worden sind, bestätigen den durch Gleichung (1) dargestellten Reaktionsablauf: Das Infrarotspektrum eines CCl4-Eluats des festen Rückstandes zeigt, daß keine POCl3-Additionsprodukte enthalten sind.
    Type of Medium: Electronic Resource
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