03 Fakultät Chemie

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    (R)- and (S)-cyanohydrins : their enzymatic synthesis and their reactions
    (1992) Effenberger, Franz
    The known enzymes (R)- and (S)-oxynitrilase catalyze the enantioselective addition of hydrocyanic acid to ldehydes to give (R)- and (S)-cyanohydrins. The optical yields can distinctly be improved by the application of organic solvents (i.e. ethyl acetate or diisopropyl ether) instead of a waterjethanol mixture which was used previously in these reactions. For the enzyme (S)-oxynitrilase Sorghum bicolor evolved to be the best source. The optically active cyanohydrins can be transformed without any racemization by acid catalyzed hydrolysis into a-hydroxy acids and by hydrogenation with lithiumjaluminum hydride into 1,2-amino alcohols. Via addition of Grignard reagents to the O-protected cyanohydrins and follow-up hydrogenation, 1,2-amino alcohols are gained with very high diastereoselectivity. By O-sulfonylation of the (R)- and (S)-cyanohydrins optically active α-sulfonyloxy nitriles are obtained. These nitriles react with various nucleophiles by complete inversion of configuration to form various α-substituted carboxylic acid derivatives, α-azido nitriles, α-amino nitriles, α-amino acids, etc.
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    Enzymatische Kohlenstoff-Kohlenstoff-Verknüpfungen
    (1993) Effenberger, Franz; Null, Volker; Straub, Alexander
    Für Dihydroxyacetonphosphat (DHAP) konnte eine einfache chemische Synthese entwickelt werden, die eine technische Anwendung von mit Kaninchenmuskel-Aldolase (RAMA) katalysierte Aldolreaktionen ermöglicht. So konnten u. a. auf diesem Wege die wichtigen Glycosidase-Inhibitoren 1-Desoxymannojirimycin (5) und 1-Desoxynojirimycin (6) in präparativen Mengen auf einfache Weise erhalten werden. Hefe-Transketolase (Hefe TK) wurde erganzend zu RAMA für stereoselektive C-C-Knüpfungen eingesetzt. Neben der Synthese der wichtigen Glycosidase-Inhibitoren 1, 4-Didesoxy-1,4-imino-D-arabinitol (12) und Fagomin (13) konnte darüber hinaus mittels Hefe TK-Katalyse ein neuer Zugang zu L-2-Hydroxyaldehyden erschlossen werden. Für präparative Anwendungen ist die neu aufgefundene Staphylococcus Carnosus-Aldolase (SCA) wegen ihrer größeren Stabilität und der einfacheren Zugänglichkeit als Katalysator für stereoselektive Aldolreaktionen besser geeignet als Kaninchenmuskel-Aldolase (RAMA).
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    Ashes of oxyfuel- and air-fired pulverised fuel combustion processes - mineralogical characterisation and long-term modification
    (2010) Schopf, Alexander; Kull, René; Massonne, Hans-Joachim; Theye, Thomas
    The focus of our work was the mineralogical analysis of ashes obtained from the combustion of soft brown coal (93.4 % huminite, 4.2 % liptinite, 0.8 % inertinite, 1.6 % pyrite and quartz; detectable amounts of Ca, Fe, Na, K, Mg, Al, Si, S, Cl in the macerals) from the open mine site Welzow-Süd in Lower Lusatia (East Germany). The combustion process was achieved in the Atmospheric Pulverized Fuel Combustion Rig (KSVA) of the Institute of Combustion and Power Plant Technology (IFK), formerly Institute of Process Engineering and Power Plant Technology (IVD) at Universität Stuttgart in air and in the oxyfuel mode. Such ashes, which form during the combustion (oxyfuel process) for power production, were characterised with the methods of polarising microscopy, X-ray diffractometry, electron microprobe analysis and carbon/water-analytics and compared with ashes from the conventional combustion process in air.