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Publikationen - Natur- und Wirkstoffchemie

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Publikation

Jimenez-Aleman, G. H.; Schöner, T.; Montero-Alejo, A. L.; Brandt, W.; Boland, W.; Improved synthesis of the chrysomelid pheromone (6R,7S)-(+)-himachala-9,11-diene via spontaneous bromination and didehydrobromination of 2,6,6,9-tetramethyl-bicyclo[5.4.0]undec-8-ene ARKIVOC 2012, 371-378, (2012) DOI: 10.3998/ark.5550190.0013.326

A convenient synthesis of (6R,7S)-(+)-himachala-9,11-diene, the pheromone of the chrysomelid beetle Phyllotreta striolata is described. The diene is obtained in a single operation by a spontaneous “bromination/dehydrobromination” of 2,6,6,9-tetramethylbicyclo[5.4.0]undec-8-ene. The halogenation/dehalogenation sequence proceeds spontaneously in CCl4, and is less uniform in CH2Cl2 and CHCl3. 1H NMR experiments carried out in presence of the radical scavenger di-tert-butyl-4-methylphenol suggest an ionic mechanism for this reaction. Theoretical calculations demonstrate that the spontaneous reaction profits from the strongly exergonic addition of Br2 to the double bond and an almost neutral energy difference between the starting olefin and the diene pheromone.
Publikation

Abbas, M.; Westermann, B.; Voelter, W.; Synthesis of 3,4-disaccharides from pyranosides and furanosides monomers, a novel class of potential bioactive disaccharides ARKIVOC 2007, 329, (2007) DOI: 10.3998/ark.5550190.0008.729

A new class of synthetically and pharmacologically important disaccharides containing epoxide moieties were synthesized from pyranoside and furanoside monomers in good to excellent yields. The scope and limitations for the formation of the linkage were evaluated.
Publikation

Zakharova, S.; Fulhorst, M.; Luczak, L.; Wessjohann, L.; Synthesis, inhibitory and activation properties of prenyldiphosphate mimics for aromatic prenylations with ubiA-prenyl transferase ARKIVOC 2004, 79, (2004) DOI: 10.3998/ark.5550190.0005.d10

4-Hydroxybenzoate oligoprenyl transferase from E. coli (ubiA-prenyl transferase) is a crucial enzyme for ubiquinone biosynthesis. It catalyzes the formation of 3-oligoprenyl-4-hydroxybenzoates like geranyl hydroxybenzoate (GHB, 23) from geranyl pyrophosphate (GPP, 22). Several analogues and mimics of geranyl pyrophosphate have been prepared for an examination of their ability to inhibit the enzyme. 7,11-Dimethyl-3-oxododeca-6,10-dienoic acid (2), 3-hydroxy7,11- dimethyldodeca-6,10-dienoic acid (3), 2-hydroxy-4,8-dimethyl-3,7-nonadienylphosphonic acid (4), and tripotassium [[(4E)-5,9-dimethyldeca-4,8-dienyl]phosphinato](difluoro)methylphosphonate (5) were synthesized from geraniol. .-2,.-1-Dihydroxylated farnesyl diphosphate 6 was prepared from trans,trans-farnesol. All compounds were tested for enzyme inhibition in a competitive assay with natural substrate. The effect of these compounds on ubiA-prenyltransferase activity varied substantially, ranging from almost full inhibition to, surprisingly, enhanced enzymatic activity at low concentrations by some compounds. A special, EDTAmodifyable magnesium effect is discussed as potential reason.
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