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  • Organic Chemistry  (21)
  • Wiley-Blackwell  (21)
  • 1990-1994  (9)
  • 1985-1989  (11)
  • 1975-1979  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Absorption and Fluorescence Studies on Neutral and Cationic Isoalloxazines (1979)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 593-608 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic properties of a variety of methylated isoalloxazine derivatives have been investigated with absorption and fluorescece techniques (Table 1). The spectral effects of methyl substitution at different positions in the isoalloxazine ring are interpreted in terms of different bond orders between the C-atoms of the methyl groups and of the aromatic ring. Methyl groups at C(6) or C(9) induce quenching of the fluorescence and shortening of the lifetime whereas a methyl group at C(7) has an opposite effect. The quenching effect might be due to strain in the molecular framework caused by the methyl groups.The lowest energy levels of the isoalloxazine cations are shifted to higher energy as compared to the neutral isoalloxazines. Apart from these shifts the trends in spectral behaviour upon methylation are similar to those observed for the neutral isoalloxazine (cf. Table 2). The fluorescence of the isoalloxazine cations is strongly quenched in auqeous solution and their lifetime much shortened. These observations indicated that there is substantial interaction between the charged fluorophore and the water dipoles and that this interaction produces efficient radiationless deactivation of the first excited singlet state.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19790620227
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  • 2
    Electronic Resource
    Electronic Resource
    Enantionselektive Synthese des L-Threonins (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 232-236 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An Enantionselective Synthesis of L-ThreonineAn enantioselective synthesis of L-threonine (1) is described. Racemic ethyl 2-acetamido-3-oxobutyrate (6) was synthesized from ethyl acetoacetate (2) [4][5] and then transformed to the epimeric optically active alcohols 7a and 7b by microbiological reduction with Saccharomyces rouxii. The Mixture 7a/7b could be converted to 1 by slightly modified, known Methods in a yield of ca. 52% with respect to 7a/7b.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700128
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  • 3
    Electronic Resource
    Electronic Resource
    Nuhn, P.; Hofmann, H.- J.: Molekulare Wirkungsmechanismen von Pharmaka. Eine Einfuhrung in die Molekularpharmakologie. - E. Hofmann, 188 S., 30 Abb., 17 Tab., Berlin: Akademie-Verlag 1985. Wissenschaftliche Taschenbücher (WTB/Biologie) Brosch. 16, - M (1985)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 327 (1985), S. 1036-1036 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19853270626
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  • 4
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 6. Acylierung von 1-Aryl-5-(2-dialkylamino-vinyl)-1 H-tetrazolen mittels Trifluor- und Trichloracetanhydrid (1993)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 335 (1993), S. 461-464 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 6. Acylation of 1-Aryl-5-(2-dialkylamino-vinyl)-1 H-tetrazoles by Trifluoro- and Trichloroacetic Anhydrides
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19933350513
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  • 5
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 7. Neuartig verknüpfte Pyrazolyl- und Isoxazolyl-tetrazole aus Enaminoketon-Vorstufen (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 79-82 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 7. New Types of Pyrazolyl- and Isoxazolyl-tetrazoles from Enamino Ketone Precursors
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360118
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  • 6
    Electronic Resource
    Electronic Resource
    Vinyloge Acylverbindungen. XXI. 1H-NMR-spektroskopische Untersuchungen an 3-Chlor-propen-iminiumsalzen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 111-114 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vinylogous Acyl Compounds. XXI. 1H-N.M.R. Spectroscopic Investigations on 3-Chloropropen-iminium SaltsThe 1H-n.m.r. data of a series of 3-aryl-3-chloropropeniminium salts 5 are reported. From the vicinal coupling constants 3J(H1, 2H) as well as from NOE difference spectra follows that salts of type 5 have throughout E(1,2)Z(2,3) configuration.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310117
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  • 7
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 5. Synthese und Umaminierung von Enaminoketonen der Tetrazolreihe (1990)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 332 (1990), S. 977-994 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 5. Synthesis and Transamination of Enamino Ketones of the Tetrazole SeriesTetrazole-5-acetaldehyde enamines 5 react with aliphatic and aromatic carboxylic acid chlorides in the presence of an auxiliary base (e.g. pyridine or triethylamine) to give tetrazolylsubstituted enamino ketones 6. The latter can be modified by acid-catalyzed transamination with secondary aliphatic amines (e.g. diethylamine, pyrrolidine, piperidine, morpholine, hexamethylene imine) yielding 5-(1-acyl-2-dialkylamino-vinyl)-1-aryl-1 H-tetrazoles 7. The analogue transamination of 6 with primary alkyl, aralkyl, and aryl amines results in corresponding secondary enamino ketones 8, which exist in solution as an equilibrium mixture of the Z and E form. Acylation of secondary tetrazole-5-acetaldehyde enamines 9 does not lead to 8, but to the isomeric N-acyl derivatives 10. - Characteristic 1H-n.m.r., u.v., and i.r. spectroscopic data of the novel products are reported.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19903320615
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  • 8
    Electronic Resource
    Electronic Resource
    Pyryliumverbindungen. 44 [1]. 2-(2-Hydroxy-3-oxo-cycloalk-1-enyl)-2H-thiopyrane aus 2,4,6-Triaryl-thiopyryliumsalzen und Cycloalkan-1,2-dionen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 853-858 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrylium Compounds. 44. 2-(2-Hydroxy-3-oxo-cycloalk-1-enyl)-2H-thiopyranes from 2,4,6-Triarylthiopyrylium Salts and Cycloalkane-1,2-diones2,4,6-Triarylthiopyrylium salts 5 react with cyclopentane-1,2-dione (2a) or cyclo-hexane-1,2-dione (2b) in the presence of an appropriate acid binding agent (e.g. sodium acetate, piperidine acetate, triethylamine/acetic acid, triethylamine) to give the hitherto unknown 2-(2-hydroxy-3-oxo-cycloalk-1-enyl)-2H-thiopyranes 6. - The structure of the novel compounds was established by n.m.r., i.r. and u.v. spectroscopic methods.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310520
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  • 9
    Electronic Resource
    Electronic Resource
    Pyryliumverbindungen. 43 [1]. Arylsubstituierte 5-(2-Dialkylamino-thiazol-5-yl)-pentadienone aus 2,4,6-Triaryl-pyryliumsalzen und 2-Dialkylamino-4-arylthiazolen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 843-852 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pyrylium Compounds. 43. Arylsubstituted 5-(2-Dialkylamino-thiazol-5-yl)-pentadienones from 2,4,6-Triarylpyrylium Salts and 2-Dialkylamino-4-aryl-thiazoles2,4,6-Triarylpyrylium salts 1 react with 2-dialkylamino-4-aryl-thiazoles 7 (used in substance or prepared in situ from α-thiocyanato-acetophenones 9) in the presence of an appropriate acid-binding agent (e.g. piperidine acetate or sodium acetate) to give 5-(2-dialkylamino-4-aryl-thiazol-5-yl)-1,3,5-triaryl-penta-2,4-dien-1-ones 8. As reaction medium aliphatic alcohols (ethanol, n-propanol), dipolar aprotic solvents (acetonitrile) or chlorinated hydrocarbons (methylene chloride, chloroform) can be used. On the other hand, under the same conditions 2-amino-4-phenyl-thiazole (10) reacts with salts of type 1 via pyrylium ring transformation yielding 2,4,6-triaryl-1-(4-phenyl-thiazol-2-yl)-pyridinium perchlorates 11.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310519
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  • 10
    Electronic Resource
    Electronic Resource
    Tetrazolverbindungen. 4 [1]. Alkylierung von 1-Aryl-5-(2-dimethylamino-vinyl)-1 H-tetrazolen (1989)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 331 (1989), S. 885-892 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrazole Compounds. 4. Alkylation of 1-Aryl-5-(2-dimethylamino-vinyl)-1 H-tetrazolesAlkylation of 1-aryl-5-(2-dimethylamino-vinyl)-1 H-tetrazoles 1 with dialkyl sulfates or alkyl iodides yields mainly 4-alkyl-1-aryl-5-(2-dimethylamino-vinyl)-1 H-tetrazolium salts which can be isolated free from isomers by separation as perchlorates 2. The reaction proceeds with retention of the E configuration of the vinyl group. In contrast to 1 the methyl groups of the dimethylamino substituent in 2 are magnetically non-equivalent indicating restricted rotation of this residue. On heating 2 with aqueous mineral acids the dimethylaminovinyl moiety undergoes degradation to a methyl group affording 4-alkyl-1-aryl-5-methyl-1 H-tetrazolium salts 4, the structure of which was confirmed by independent synthesis. With hot aqueous alkali hydroxide 2 reacts under ring cleavage to give aryl azide.  -  1H n.m.r. and u.v. spectroscopic data of the tetrazolium salts 2 and 4 are reported.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19893310602
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