3934-84-7Relevant articles and documents
Exploring the Selective Demethylation of Aryl Methyl Ethers with a Pseudomonas Rieske Monooxygenase
Lanfranchi, Elisa,Trajkovi?, Milo?,Barta, Katalin,de Vries, Johannes G.,Janssen, Dick B.
, p. 118 - 125 (2019)
Biocatalytic dealkylation of aryl methyl ethers is an attractive reaction for valorization of lignin components, as well as for deprotection of hydroxy functionalities in synthetic chemistry. We explored the demethylation of various aryl methyl ethers by using an oxidative demethylase from Pseudomonas sp. HR199. The Rieske monooxygenase VanA and its partner electron transfer protein VanB were recombinantly coexpressed in Escherichia coli and they constituted at least 25 % of the total protein content. Enzymatic transformations showed that VanB accepts NADH and NADPH as electron donors. The VanA–VanB system demethylates a number of aromatic substrates, the presence of a carboxylic acid moiety is essential, and the catalysis occurs selectively at the meta position to this carboxylic acid in the aromatic ring. The reaction is inhibited by the by-product formaldehyde. Therefore, we tested three different cascade/tandem reactions for cofactor regeneration and formaldehyde elimination; in particular, conversion was improved by addition of formaldehyde dehydrogenase and formate dehydrogenase. Finally, the biocatalyst was applied for the preparation of protocatechuic acid from vanillic acid, giving a 77 % yield of the desired product. The described reaction may find application in the conversion of lignin components into diverse hydroxyaromatic building blocks and generally offers potential for new, mild methods for efficient unmasking of phenols.
Regioselective para-Carboxylation of Catechols with a Prenylated Flavin Dependent Decarboxylase
Payer, Stefan E.,Marshall, Stephen A.,B?rland, Natalie,Sheng, Xiang,Reiter, Tamara,Dordic, Andela,Steinkellner, Georg,Wuensch, Christiane,Kaltwasser, Susann,Fisher, Karl,Rigby, Stephen E. J.,Macheroux, Peter,Vonck, Janet,Gruber, Karl,Faber, Kurt,Himo, Fahmi,Leys, David,Pavkov-Keller, Tea,Glueck, Silvia M.
supporting information, p. 13893 - 13897 (2017/10/09)
The utilization of CO2 as a carbon source for organic synthesis meets the urgent demand for more sustainability in the production of chemicals. Herein, we report on the enzyme-catalyzed para-carboxylation of catechols, employing 3,4-dihydroxybenzoic acid decarboxylases (AroY) that belong to the UbiD enzyme family. Crystal structures and accompanying solution data confirmed that AroY utilizes the recently discovered prenylated FMN (prFMN) cofactor, and requires oxidative maturation to form the catalytically competent prFMNiminium species. This study reports on the in vitro reconstitution and activation of a prFMN-dependent enzyme that is capable of directly carboxylating aromatic catechol substrates under ambient conditions. A reaction mechanism for the reversible decarboxylation involving an intermediate with a single covalent bond between a quinoid adduct and cofactor is proposed, which is distinct from the mechanism of prFMN-associated 1,3-dipolar cycloadditions in related enzymes.
DPPH (=2,2-diphenyl-1-picrylhydrazyl) radical-scavenging reaction of protocatechuic acid (=3,4-dihydroxybenzoic acid): Difference in reactivity between acids and their esters
Saito, Shizuka,Kawabata, Jun
, p. 1395 - 1407 (2007/10/03)
Prolocatechuic acid (=3,4-dihydroxybenzoic acid; 1) exhibits a significantly slow DPPH (=2,2-diphenyl-1-picrylhydrazyl) radical-scavenging reaction compared to its esters in alcoholic solvents. The present study is aimed at the elucidation of the difference between the radical-scavenging mechanisms of protocatechuic acid and its esters in alcohol. Both protocatechuic acid (1) and its methyl ester 2 rapidly scavenged 2 equiv. of radical and were converted to the corresponding o-quinone structures 1a and 2a, respectively (Scheme). Then, a regeneration of catechol (=benzene-1,2-diol) structures occurred via a nucleophilic addition of a MeOH molecule to the o-quinones to yield alcohol adducts 1f and 2c, respectively, which can scavenge additional 2 equiv. of radical. However, the reaction of protocatechuic acid (1) beyond the formation of the o-quinone was much slower than that of its methyl ester 2. The results suggest that the slower radical-scavenging reaction of 1 compared to its esters is due to a dissociation of the electron-withdrawing carboxylic acid function to the electron-donating carboxylate ion, which decreases the electrophilicity of the o-quinone, leading to a lower susceptibility towards a nucleophilic attack by an alcohol molecule.
