- Biocatalytic racemization of (hetero)aryl-aliphatic α- hydroxycarboxylic acids by Lactobacillus spp. proceeds via an oxidation-reduction sequence
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The biocatalytic racemization of a range of (hetero)aryl- and (di)aryl-aliphatic α-hydroxycarboxylic acids has been achieved by using whole resting cells of Lactobacillus spp. The essentially mild (physiological) reaction conditions ensure the suppression of undesired side reactions, such as elimination, decomposition or condensation. Cofactor/inhibitor studies using a cell-free extract of Lactobacillus paracasei DSM 20207 reveal that the addition of redox cofactors (NAD+/NADH) leads to a distinct increase in the racemization rate, while strong inhibition is observed in the presence of Thio-NAD+, which suggests that the racemization proceeds by an oxidation-reduction sequence rather than involvement of a "racemase" enzyme. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Nestl, Bettina M.,Glueck, Silvia M.,Hall, Melanie,Kroutil, Wolfgang,Stuermer, Rainer,Hauer, Bernhard,Faber, Kurt
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p. 4573 - 4577
(2007/10/03)
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- Unstable 1,1,2-Enetriols as (Probable) Intermediates in the Decarboxylation of α,β-Diketo Acids
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During the acid hydrolysis of (hydrated) 4-aryl-2,3-diketobutyramide 2 (aryl = phenyl, o-chlorophenyl, p-methoxyphenyl), 3-aryllactic acid (5) is formed by rapid decarboxylation of the intermediate diketo acid (3).In the decarboxylation step, a further unstable intermediate is formed.The latter manifests itself by reducing 1 mol of added iodine during the hydrolysis-decarboxylation reaction, thereby forming 3-arylpyruvic acid (6), isolated instead of 5.Thus, the oxidation of the unstable intermediate by iodine is more rapid than its ketonization.It is formulated as an 1,1,2-enetriol (4), more probably than an α-hydroxyketone.
- Dahn, Hans,Rotzler, Gerhard
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p. 3080 - 3082
(2007/10/02)
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