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Dive into the research topics where Ernst Kupfer is active.

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Featured researches published by Ernst Kupfer.


Journal of Biological Chemistry | 1997

Tracer Studies with Crude U-13C-Lipid Mixtures BIOSYNTHESIS OF THE LIPASE INHIBITOR LIPSTATIN

Wolfgang Eisenreich; Ernst Kupfer; Wolfgang Weber; Adelbert Bacher

The biosynthesis of the pancreatic lipase inhibitor lipstatin was investigated by fermentation experiments using cultures of Streptomyces toxytricini, which were supplied with soybean oil and a crude mixture of U-13C-lipids obtained from algal biomass cultured with 13CO2. Lipstatin was analyzed by one- and two-dimensional NMR spectroscopy. 13C total correlation spectroscopy and INADEQUATE experiments show that two fatty acid fragments containing 14 and 8 carbon atoms, respectively, are incorporated en bloc into lipstatin. The 14-carbon fragment is preferentially derived from the unsaturated fatty acid fraction, as shown by an experiment with hydrogenated U-13C-lipid mixture, which is conducive to labeling of the 8-carbon moiety but not of the 14-carbon moiety. The data indicate that the lipstatin molecule can be assembled by Claisen condensation of octanoyl-CoA with 3-hydroxy-Δ5,8-tetradecanoyl-CoA obtained by β oxidation of linoleic acid. The formation of lipstatin from acetate units by a polyketide-type pathway is ruled out conclusively by these data. The data show that surprisingly clear labeling patterns can be obtained in studies with crude, universally 13C-labeled precursor mixtures that are proffered together with a large excess of unlabeled material. One- and two-dimensional 13C total correlation spectroscopy analyses are suggested as elegant methods for the delineation of contiguously 13C-labeled biosynthetic blocks.


ChemMedChem | 2008

Metabolite Identification via LC-SPE-NMR-MS of the In vitro Biooxidation Products of a Lead mGlu5 Allosteric Antagonist and Impact on the Improvement of Metabolic Stability in the Series

Simona M. Ceccarelli; Götz Schlotterbeck; Patrick Boissin; Martin Binder; Bernd Buettelmann; Steven Paul Hanlon; Georg Jaeschke; Sabine Kolczewski; Ernst Kupfer; Jens-Uwe Peters; Richard Hugh Philip Porter; Eric Prinssen; Marianne Rueher; Iris Ruf; Will Spooren; Andreas Stämpfli; Eric Vieira

Detailed information on the metabolic fate of lead compounds can be a powerful tool for an informed approach to the stabilization of metabolically labile compounds in the lead optimization phase. The combination of high performance liquid chromatography (HPLC) with nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) has been used to give comprehensive structural data on metabolites of novel drugs in development. Recently, increased automation and the embedding of on‐line solid‐phase extraction (SPE) into a integrated LC‐SPE‐NMR‐MS system have improved enormously the detection limits of this approach. The new technology platform allows the analysis of complex mixtures from microsome incubations, combining low material requirements with relatively high throughput. Such characteristics make it possible to thoroughly characterize metabolites of selected compounds at earlier phases along the path to lead identification and clinical candidate selection, thus providing outstanding guidance in the process of eliminating undesired metabolism and detecting active or potentially toxic metabolites. Such an approach was applied at the lead identification stage of a backup program on metabotropic glutamate receptor 5 (mGlu5) allosteric inhibition. The major metabolites of a lead 5‐aminothiazole‐4‐carboxylic acid amide 1 were synthesized and screened, revealing significant in vitro activity and possible involvement in the overall pharmacodynamic behavior of 1. The information collected on the metabolism of the highly active compound 1 was pivotal to the synthesis of related compounds with improved microsomal stability.


Bioorganic & Medicinal Chemistry | 1994

Large scale preparation of chiral building blocks for the P3 site of renin inhibitors

Stephan Doswald; Heinrich Estermann; Ernst Kupfer; Heinz Stadler; Willi Walther; Thomas Weisbrod; Beat Wirz; Wolfgang Wostl

Racemic ethyl 2-benzyl-3-(tert-butylsulfonyl)propionate (1) and racemic ethyl 2-benzyl-3-[[1-methyl-1-((morpholin-4-yl)carbonyl)ethyl]sulfonyl] propionate (3) were enantioselectively hydrolyzed by subtilisin Carlsberg generating the respective (S)-acids used as building blocks for renin inhibitors. The esters were readily converted as emulsions at elevated temperature, in a suspended form or a two-phase-liquid system. The enzyme maintained its excellent selectivity and a good activity also at high initial substrate concentrations (up to 50% w/w). The enzymatic reaction and work-up were optimized and scaled up. Emulsion problems during work-up encountered with these highly concentrated mixtures were solved by application of a disk separator for phase separation.


The Journal of Antibiotics | 1987

LIPSTATIN, AN INHIBITOR OF PANCREATIC LIPASE, PRODUCED BY STREPTOMYCES TOXYTRICINI

Ernst Karl Weibel; Paul Hadvary; Erich Hochuli; Ernst Kupfer; Hans Lengsfeld


Helvetica Chimica Acta | 1983

Production of (+)-(S)-ethyl 3-hydroxybutyrate and (-)-(R)-ethyl 3-hydroxybutyrate by microbial reduction of ethyl acetoacetate.

Beat Wipf; Ernst Kupfer; Roberto Bertazzi; Hans Georg Wilhelm Leuenberger


The Journal of Antibiotics | 1991

Anantin-a peptide antagonist of the atrial natriuretic factor (ANF). I. Producing organism, fermentation, isolation and biological activity

Wolfgang Weber; W. Fischli; Erich Hochuli; Ernst Kupfer; Ernst Karl Weibel


Archive | 1984

Hexadecanoic acid and hexadecadienoic-acid derivatives

Paul Hadvary; Erich Hochuli; Ernst Kupfer; Hans Lengsfeld; Ernst Karl Weibel


Helvetica Chimica Acta | 1979

Stoffwechselprodukte von Mikroorganismen. 186. Mitteilung. Über die Aspochalasine A, B, C und D†‡

Walter Keller-Schierlein; Ernst Kupfer


Helvetica Chimica Acta | 1981

Stoffwechselprodukte von Mikroorganismen 205. Mitteilung.. Isolierung und Struktur von Streptazolin

Hannelore Drautz; Hans Zähner; Ernst Kupfer; Walter Keller-Schierlein


Helvetica Chimica Acta | 1982

Stoffwechselprodukte von Mikroorganismen. 210. Mitteilung. Über die Avilurekanosen A and C and weitere Abbauprodukte Avilamycine A and C

Ernst Kupfer; Katarina Neupert-Laves; Max Dobler; Walter Keller-Schierle

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