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  • Articles  (69)
  • 1995-1999  (69)
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  • 11
    Electronic Resource
    Electronic Resource
    New syntheses of 2,4-diaminopyrroles and aminopyrrolinones (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 933-943 
    Details
    ISSN: 1434-4475
    Keywords: Thorpe-Ziegler cyclization ; (Oxazolin-2-yliden)malononitrile ; 2,4-Diamino-pyrrole ; 2-Amino-4-oxo-pyrrol-3-carbonitrile ; 4-Amino-2-oxo-pyrrol-3-carbonitrile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Oxazolin-2-yliden-malononitrile3a–d. die aus Thioketenaminalen und α-Halogenketonen erhalten wurden, reagieren mit primären und sekundären Aminen zu den 2,4-Diaminopyrrolen5a–h. Mercaptobenzol als nukleophiles Reagens liefert 4-Amino-2-phenylthiopyrrol (5j). Analog wurden Cyan-(3,5-diphenyl-3H-oxazol-2-yliden)-essigsäuremethylester als Zwischenprodukte für die Synthese der 2-Amino-4-oxo-pyrroline10a–d hergestellt. Die isomeren 4-Amino-2-oxo-pyrroline13a–d können aus den 4-Amino-2-methoxy-pyrrolen11a,b erhalten werden, was als Nachweis für die Position der Substituenten dient. Die Verbindungen wurden1H- und13C NMR-spektroskopisch untersucht.
    Notes: Summary Oxazolin-2-ylidene-malononitriles3a–d, obtainable from thioketenaminals and α-halogen-ketones, react with primary and secondary amines to afford 2,4-diamino-pyrroles5a–h. Mercaptobenzen as nucleophilic agent gives the 4-amino-2-phenylthio-pyrrole5j. Analogously, cyano-(3,5-diphenyl-3H-oxazol-2-ylidene)-acetic acid methyl esters were prepared as intermediates for the synthesis of 2-amino-4-oxo-pyrrolines10a–d. The isomeric 4-amino-2-oxo-pyrrolines13a–d can be obtained from 4-amino-2-methoxy-pyrroles, which serves as proof for the position of substituents. The structures were investigated by1H and13C NMR spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807103
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  • 12
    Electronic Resource
    Electronic Resource
    Irradiation-induced atomic defects in SiC studied by positron annihilation (1995)
    Springer
    Applied physics 61 (1995), S. 51-53 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 61.70; 61.80; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract.  The present paper reports on positron lifetime measurements on atomic defects in SiC after low-temperature (80 K) electron irradiation of low (0.47 MeV) and high (2.5 MeV) electron energies and doses from 1.8×1017 to 1.9×1019 e/cm2 as well as after subsequent isochronal annealing up to 1900 K. For these studies the single crystals of nitrogen doped (2-3×1018 cm-3) SiC grown by a modified Lely technique with hexagonal structure (6H polytype) were used. According to the positron lifetime measurements, very different types of vacancy-like positron traps are introduced after irradiation with electrons of either low or high energy. The formation of defect agglomerates and their decay at high temperatures is studied during isochronal annealing and related to earlier studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538210
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  • 13
    Electronic Resource
    Electronic Resource
    Irradiation-induced atomic defects in SiC studied by positron annihilation (1995)
    Springer
    Applied physics 61 (1995), S. 51-53 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The present paper reports on positron lifetime measurements on atomic defects in SiC after low-temperature (80 K) electron irradiation of low (0.47 MeV) and high (2.5 MeV) electron energies and doses from 1.8×1017 to 1.9×1019 e/cm2 as well as after subsequent isochronal annealing up to 1900 K. For these studies the single crystals of nitrogen doped (2–3×1018 cm−3) SiC grown by a modified Lely technique with hexagonal structure (6H polytype) were used. According to the positron lifetime measurements, very different types of vacancy-like positron traps are introducted after irradiation with electrons of either low or high energy. The formation of defect agglomerates and their decay at high temperatures is studied during isochronal annealing and related to earlier studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538210
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  • 14
    Electronic Resource
    Electronic Resource
    Bioconversion of sunflower oil, rapeseed oil and ricinoleic acid by Candida tropicalis M25 (1998)
    Springer
    Applied microbiology and biotechnology 50 (1998), S. 573-578 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Bioconversions of sunflower oil and rapeseed oil in fed-batch cultures fermented with Candida tropicalis M25 were studied. Cofermentations with palmitic acid resulted in successful transformations to different 3-hydroxydioic acids. The absolute configuration of the major fermentation product, R-(Z)-3-hydroxy-9-octadecenedioic acid, was determined by comparison of the 1H NMR data with those of an authentic, optically pure compound. Using ricinoleic acid as the sole carbon source, the optically pure R-(Z)-7-hydroxy-9-octadecenedioic acid was obtained at a maximum concentration of 4.2 g/l. In addition to the hydroxydioic acid, (Z)-3,12-dihydroxy-9-octadecenedioic acid was also produced following fermentation with the mutant M25.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051337
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  • 15
    Electronic Resource
    Electronic Resource
    Biotransformation of linoleic acid with the Candida tropicalis M25 mutant (1997)
    Springer
    Applied microbiology and biotechnology 48 (1997), S. 83-87 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Linoleic acid was transformed by mutant Candida tropicalis M25 and transformations were studied in batch and fed-batch cultures. Cofermentations with palmitic acid as inducer of the fatty acid degradation pathway were performed. Besides the (Z),(Z)-octadeca-6,9-dienedioic acid, (Z),(Z)-3-hydroxyoctadeca-9,12-dienedioic acid and (Z),(Z)-3-hydroxytetradeca-5,8-dienedioic acid were obtained as the main fermentation products. The maximum concentrations of (Z),(Z)-octadeca-6,9-dienedioic acid and (Z),(Z)-3-hydroxyoctadeca-9,12-dienedioic acid reached values of 6.4 g/l and 6.9 g/l respectively. The structures of the products were characterized by chemical and spectroscopic methods. The configuration of the double bonds was not changed during bioconversion. As only one regioisomer of the hydroxylated fatty acid was detected, the hydroxylation is site-specific.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530051019
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  • 16
    Electronic Resource
    Electronic Resource
    Substituierte 2-Alkoxy-5-amino- und-2,5-diamino-imidazole aus Oxazol-2-yliden-cyanamiden (1996)
    Springer
    Monatshefte für Chemie 127 (1996), S. 313-318 
    Details
    ISSN: 1434-4475
    Keywords: (2-Alkoxy-5-amino-imidazol-4-yl)-ketones ; N-Cyano-S-methyl-isothioureases ; (2.5-Di-amino-imidazol-4-yl)-ketones ; α-Halogenketones ; Oxazol-2-yliden-cyanamides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary N-Cyano-S-methyl-isothio-ureases (1) react with α-halogen ketones (2) by ring closure yielding the (3H-oxazol-2-yliden)-cyanamides3. by ring transformation, 2-Alkoxy-5-amino-1-phenyl-3H-imidazol-4-yl)-ketones (4) are formed. Primary and secondary amines react with3 to give 2-N-alkylated (2,5-Diamino-1-phenyl-3H-imidazol-4-yl)-ketones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813797
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  • 17
    Electronic Resource
    Electronic Resource
    Syntheses with pyridinium and sulfonium salts of acylated β-enaminonitriles (1995)
    Springer
    Monatshefte für Chemie 126 (1995), S. 711-723 
    Details
    ISSN: 1434-4475
    Keywords: Malononitrile ; Benzoles ; Pyridines ; Thiophenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Pyridinium- und Sulfoniumsalze2a–e, die aus 3-Amino-2-(α-halo-acetyl)-crotonsäurenitril und 3-Amino-2-(α-halo-acetyl)-zimtsäurenitril hergestellt werden können, reagieren mit Malonsäuredinitril in Gegenwart einer Base zu 3-Amino-2-pyridinio-phenolaten3a,b und 3-Amino-2-sulfonio-phenolaten3c–e. In Analogie wurden 3-Amino-2-(diethyloxyphosphoryl)-phenol5a und 3-Amino-2-(p-tolyl-sulfonyl)-phenol5b erhalten. 2,3-Diamino-phenole6a,b werden aus den Pyridiniumsalzen3a,b gebildet. Das Verhalten der Pyridiniumsalze2a,b gegenüber Heterokumulenen ist untersucht worden. Cyanamid führt zum (2-Amino-4-hydroxy-pyrid-3-yl)-pyridiniumsalz8c. Phenylisothiocyanat liefert die 3-Pyridinio-2-thioxo-pyridin-4-olate9a,b. In Abhängigkeit vom Substituenten in der Position 6 entsteht bei der Reaktion mit Schwefelkohlenstoff ein 3-Pyridinio-2-thioxo-pyridin-4-olat10 oder ein 3-Pyridinio-2-thioxo-thiopyran-4-olat11. Phenylisocyanat reagiert zum Pyrimidin-2,4-dion12 unter Verlust von N-Methyl-pyridiniumchlorid. S-Methylierung von9a und Spaltung des Pyridiniumringes ergibt das 3-Amino-2-methylthio-pyrid-4-on14. Die Verbindungen wurden1H- und13C-NMR-spektroskopisch untersucht.
    Notes: Summary Pyridinium and sulfonium salts2a–e which can be prepared from 3-amino-2-(α-haloacetyl)-crotonitriles and 3-amino-2-(α-halo-acetyl)-3-phenyl-acrylonitriles react with malononitrile in the presence of a base to 3-amino-2-pyridinio-phenolates3a,b and 3-amino-2-sulfonio-phenolates3c–e. In an analogous way, 3-amino-2-(diethyloxyphosphoryl)-phenol5a and 3-amino-2-(p-tolyl-sulfonyl)-phenol5b have been prepared. 2,3-Diamino-phenoles6a,b are formed from the pyridinium salts3a,b. The behaviour of the pyridinium salts2a,b towards heterocumulenes has been investigated. Cyanamide leads to the (2-amino-4-hydroxy-pyrid-3-yl)-pyridinium salt8c. Phenylisothiocyanate gives the 3-pyridinio-2-thioxo-pyridin-4-olates9a,b. Carbon disulfide gives rise to 3-pyridinio-2-thioxo-pyridin-4-olate10 or 3-pyridinio-2-thioxo-thiopyran-4-olate11, depending on the substituent at the 6-position. Phenylisocyanate reacts to the pyrimidin-2,4-dione12 with loss of N-methyl-pyridinium chloride. S-methylation of9a and cleavage of the pyridine moiety yields the 3-amino-2-methylthio-pyrid-4-one14. The structures were investigated by1H and13C NMR spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807162
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  • 18
    Electronic Resource
    Electronic Resource
    Schriftenschau (1999)
    Springer
    Journal of ornithology 140 (1999), S. 207-210 
    Details
    ISSN: 1439-0361
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01653600
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  • 19
    Electronic Resource
    Electronic Resource
    Amino-thieno[2,3-c]pyrazole und Amino-thieno[2,3-b]pyrrole (1995)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 472-477 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino-thieno[2,3-c]pyrazoles and Amino-thieno[2,3-b]pyrrolesThe synthesis of thieno[2,3-c]pyrazoles and thieno[2,3-b]pyrroles is described. From the dithioliumsalt (1) and potassium hydroxide the potassium-(2,2-dicyan-1-methylthio-ethen-1-yl)-thiolate (2) is formed. This reacts with hydrazine hydrate to form the 3-amino-5-thioxo-pyrazol-4-carbonitrile (3) S-Alkylation with α-chlorocarbonyl compounds yielding (6a-c) leads via Thorpe-Ziegler-cyclization to 3,4-diamino-thieno[2,3-c]pyrazoles (9) if the position 1 is alkylated (8). Acetyl acetone yields 2-mercapto-pyrazolo[1,5-a]pyrimidine (5). After S-alkylation (10a-d) are immediately cyclized to thieno [2′,3′:3,4]pyrazolo[1,5-a]pyrimidine (11a-d). The ketone (6a) can be cyclized to the pyrazolo [5,1-b]thiazole (12). 3 reacts with oxalyl chloride to form the 2,3-dioxo-6-thioxo-imidazo[1,2-b]pyrazole (13) of which S-phenacyl derivative (14) because the NH-proton cannot be cyclized. The 5-amino-3,4-dicyano-pyrrol-2-thiolate (16) shows the analogous behaviour. The S-alkylation is followed by cyclization, and 3,5-diamino-thieno[2,3-b]pyrroles (18a-b) arise. Reaction of 5-amino-2-alkylthio-pyrrol-3,5-dicarbonitrile (17) with acetyl acetone provides pyrrolo[1,2-a]pyrimidine (20a-c) which can be cyclized to form thieno[3′,2′:4,6]pyrimidines (21a-c) very easily.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199533701101
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  • 20
    Electronic Resource
    Electronic Resource
    Neue Synthese von substituierten 4-Amino-chinazolinen und deren Heteroanalogen (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 206-213 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Synthesis of Substituted 4-Amino-quinazolines and Their HeteroanalogaN-Chloracetyl-anthranilonitriles react with potassium thiocyanate in the presence of alcohol to the (4-aminoquinazolin-2-yl-thio)-acetic acid ester (5). In the presence of water or primary amine the acetic acid derivative (6) or the acetic acid amide derivatives (7) are obtained. 2,4-Diaminoquinazolines (8) arise if vigorous reaction conditions are employed. With 2-chloracetylamino-cyclopent-1-en-carbonitrile as starting material the pyrimidines (11) are formed from the reaction with potassium thiocyanate. Analogously, (4-pyrimidyl-2-yl-seleno)-acetic acid ester (12) and (thiazolo[4,5-d]pyrimid-2-yl-seleno)-acetic acid derivatives (16) can be prepared with potassium selenocyanate. N-Chloracetyl derivatives of 5-membered heterocycles with enamino-nitrile structure (13, 15, 18, 20) react with potassium thiocyanate to yield thieno[2,3-d]-, thiazolo[4,5-d]-, pyrrolo[2,3-d]-, furo[2,3-d]- and pyrazolo[4,3-d]pyrimidines (14, 16, 19a, 19b, 21).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380144
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