- Linum usitatissimum hydroxynitrile lyase cross-linked enzyme aggregates: A recyclable enantioselective catalyst
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An immobilized form of the hydroxynitrile lyase from Linum usitatissimum (LuHNL) as cross-linked enzyme aggregate (CLEA) with high specific activity (303.5 U/g) and recovery (33%) was developed. Molecular imprinting using 2-butanone as additive in the immobilization process improved the synthetic activity of the biocatalyst. LuCLEA could be partially recycled for the synthesis of (R)-2-butanone cyanohydrin on a preparative scale over two batches. The enantioenriched cyanohydrin obtained was further hydrolyzed to give (R)-2-hydroxy-2-methylbutyric acid in 85% yield (from 2-butanone) and 87% ee.
- Cabirol, Fabien L.,Pei, Loo Tan,Tay, Benson,Cheng, Shiryn,Hanefeld, Ulf,Sheldon, Roger A.
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experimental part
p. 2329 - 2338
(2009/10/23)
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- Process for preparing optically active α-hydroxy acids and derivatives thereof
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The present invention provides a process for preparing optically active α-hydroxy acids and derivatives thereof by subjecting the alkylated 1,3-dioxolanones of formula (IV) wherein R1and R2are the same or different and are each independently H or C1-6alkyl; R5is H, C1-16alkyl, or unsubstituted or substituted phenyl; and R6is C1-8alkyl, C2-7alkenyl or unsubstituted or substituted benzyl, to either alcoholysis or hydrolysis, in which the alkylated 1,3-dioxolanones are obtained by using 10-camphorsulfonamide as a chiral auxiliary.
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Page/Page column 19
(2008/06/13)
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- Enantioselective synthesis of α-hydroxy acids employing (1S)-(+)-N,N-diisopropyl-10-camphorsulfonamide as chiral auxiliary
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matrix presented I R1=H, Me, Ph II (>98 de.) III Lewis acid (BF3·-OEt2) catalyzed condensation of dimethoxy acetal 2 with α-hydroxy acids produces chiral 1,3-dioxolanones I. The enolates derived from these compounds underg
- Chang, Jia-Wen,Jang, Der-Pin,Uang, Biing-Jiun,Liao, Fen-Ling,Wang, Sue-Lein
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p. 2061 - 2063
(2008/02/09)
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- Enzyme-catalyzed synthesis of (R)-ketone-cyanohydrins and their hydrolysis to (R)-α-hydroxy-α-methyl-carboxylic acids
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(R)-Ketone-cyanohydrins (R)-2 are obtained with high enantioselectivity from aliphatic ketones 1 and HCN in organic solvents using (R)-oxynitrilase ( EC 4.1.2.10) as catalyst. Acid catalyzed hydrolysis of the cyanohydrins (R)-2 affords the corresponding (R)-α-hydroxy-α-methyl-carboxylic acids (R)-3 without measurable racemization.
- Effenberger,Horsch,Weingart,Ziegler,Kuhner
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p. 2605 - 2608
(2007/10/02)
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- Stereoelectronic Control of the Tertiary Ketol Rearrangement: Implications for the Mechanism of the Reaction Catalysed by the Enzymes of Branched-chain Amino Acid Metabolism, Reductoisomerase and Acetolactate Decarboxylase
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The alkali-catalised rearrangement of (R)--3-hydroxy-3-methylpentan-2-one has been studied.Rearrangement via transition state having an anti arrangement of C-O bonds was preferred over that with a syn arrangement by a factor of 1.8:1.The result is of interest in relation to the mechanism of action of the enzymes reductoisomerase and acetolactate decarboxylase, both of which are involved in the metabolism of the branched-chain amino acids.The structure and relative configuration of the product 23 of bromolactonisation of N-methacryloyl L-proline 22 were determined by X-ray crystallographic analysis.
- Crout, David H. G.,McIntyre, C. Rupert,Alcock, Nathaniel W.
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- ELECTROPHILIC ASYMMETRIC SYNTHESES OF α-HYDROXY CARBOXYLIC ACIDS
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Asymmetric electrophilic syntheses of α-hydroxy carboxylic acids from chiral amide derivatives of tert-butyl- and trialkylsilyl- protected glycolic and lactic acids are described which lead to chiral α-hydroxy carboxylic acids in 60-95percent diastereomeric excess.
- Ludwig, Jerry W.,Newcomb, Martin,Bergbreiter, David E.
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p. 2731 - 2734
(2007/10/02)
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- α-ALKYLATION OF α-HETEROSUBSTITUTED CARBOXYLIC ACIDS WITHOUT RACEMIZATION; EPC-SYNTHESES OF TERTIARY ALCOHOLS AND THIOLS
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α-Hydroxy- and α-mercapto-carboxylic acids are condensed with pivalaldehyde to give 2-t-butyl-5-substituted-1,3-dioxolanones or 1,3-oxathiolanones (2); the predominate cis-isomers are separeted by crystallization.The cis-disubstituted heterocycles 2 derived from lactic, mandelic and malic acid funish, after deprotonation with LDA, reaction with electrophiles such as alkyl halides, aldehydes and ketones, and hydrolysis α-branched α-hydroxy-carboxylic acids (3, 6, 8, 9, 10).These result from an overall substitution of the proton in the α-CO position with retention of configuration.The optically active carboxylic acids are α-alkylated without racemization and without employment of a chiral auxiliary ("self-reproduction of chirality", Scheme 1).The diastereoselectivities (ds) are generally >95percent (Table 1, 2, and 20-25).
- Seebach, Dieter,Naef, Reto,Calderari, Giorgio
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p. 1313 - 1324
(2007/10/02)
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