- Chemo- And stereoselective reduction of β-keto-α-oximino nitriles by using baker's yeast
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The baker's yeast mediated reduction of β-keto-α-oximino nitriles 3 at 20 ° C gave β-hydroxy-α-oximino nitriles 4 in high yields with high enantiomeric purity [enantiomeric excess (ee) values >99%]. At room temperature, the same reaction afforded the product in a slightly lower yield. The β-hydroxy-α-oximino nitriles 4 were obtained as single stereoisomers according to chiral GC-MS analyses and the 1H and 19F NMR spectra of the corresponding Mosher esters. The abso-lute stereochemistry of alcohol 4a was determined by hydrolysis of its oximino nitrile group followed by conversion into its corresponding α-hydroxy ester. The β-hydroxy-α-oximino nitrile products were further submitted to oxime- and nitrileselective transformations. This chemo- and stereoselective reduction can be used to generate important chiral building blocks.
- Mo, Kilwoong,Kang, Soon Bang,Kim, Youseung,Lee, Yong Sup,Lee, Jae Wook,Keum, Gyochang
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p. 1137 - 1143
(2015/02/19)
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- Candida tenuis xylose reductase catalyzed reduction of aryl ketones for enantioselective synthesis of active oxetine derivatives
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Candida tenuis xylose reductase shows high catalytic efficiencies in carbonyl reduction of acetophenone and 1-phenyl-1-propanone derivatives. The quite low substrate solubility in aqueous buffer systems is circumvented by addition of methanol or by two-phase solvent systems. In the latter, methanol improves the substrate phase transfer as solvent mediator and leads to reasonable space/time yields. Resulting enantiomerically pure chiral alcohols are key intermediates for synthesis of active pharmaceutical ingredients. (R)-Atomoxetine is exemplarily synthesized in four steps, and the further use for generation of other oxetine derivatives and a polo-like kinase 1 inhibitor are discussed. Copyright
- Vogl, Michael,Brecker, Lothar,Kratzer, Regina,Nidetzky, Bernd
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p. 847 - 853,7
(2020/07/31)
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- Pyrimidine-based inhibitors of dipeptidyl peptidase IV and methods
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Compounds are provided having the formula (I) wherein R, B, X and Y are as defined herein.
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Page/Page column 16-17
(2008/06/13)
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- Unexpected stereorecognition in nitrilase-catalyzed hydrolysis of β-hydroxy nitriles
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Biocatalytic enantioselective hydrolysis of β-hydroxy nitriles to corresponding (S)-enriched β-hydroxy carboxylic acids has been achieved for the first time by an isolated nitrilase bII6402 from Bradyrhizobium japonicum USDA110. This offers a new "green" approach to optically pure β-hydroxy nitriles and β-hydroxy carboxylic acids. The observed remote stereorecognition is surprising because this nitrilase shows no enantioselectivity for the hydrolysis of α-hydroxy nitriles such as mandelonitrile.
- Kamila, Sukanta,Zhu, Dunming,Biehl, Edward R.,Hua, Ling
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p. 4429 - 4431
(2007/10/03)
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- Synthesis of mono- and disubstituted 1H-imidazo[1,2-b]pyrazoles
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The improved synthesis of 1H-imidazo[1,2-b]pyrazole 1 and of mono- and disubstituted derivatives is described and representative experimental procedures are given. Namely, 2-, 3-, 7- and 6-monosubstituted (2-15k), 2,3- and 6,7-disubstituted (16,17) compounds are prepared and characterized.
- Seneci,Nicola,Inglesi,Vanotti,Resnati
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p. 311 - 341
(2007/10/03)
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- Preparation of halogenated quinolonecarboxylic acids
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The invention is a process of making the compounds of the structure STR1 wherein R is alkyl with 1-3 carbon atoms, 2-fluoroethyl, phenyl or cyclopropyl, X is halogen, and X1 and X2 each independently is hydrogen or halogen. The compounds are useful as intermediates for quinoline antibacterial compounds.
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