10548-77-3Relevant academic research and scientific papers
Role of laccase as an enzymatic pretreatment method to improve lignocellulosic saccharification
Heap, Lucy,Green, Anthony,Brown, David,Van Dongen, Bart,Turner, Nicholas
, p. 2251 - 2259 (2014)
The recalcitrant nature of lignocellulose, in particular due to the presence of lignin, is found to decrease the efficiency of cellulases during the saccharification of biomass. The efficient and cost effective removal of lignin is currently a critical bi
Solar photochemical oxidations of benzylic and allylic alcohols using catalytic organo-oxidation with DDQ: Application to lignin models
Walsh, Katie,Sneddon, Helen F.,Moody, Christopher J.
, p. 5224 - 5227 (2014)
Visible light has a dramatic effect on the oxidation of benzylic and allylic alcohols, including those deactivated by electron-withdrawing groups, and β-O-4 lignin models, using catalytic amounts of the organo-oxidant 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Sodium nitrite or tert-butyl nitrite is used as cocatalyst, and oxygen is employed as the terminal oxidant.
Cleavage of CC and Co bonds in β-O-4 linkage of lignin model compound by cyclopentadienone group 8 and 9 metal complexes
Kishino, Masamichi,Kusumoto, Shuhei,Nozaki, Kyoko
, p. 477 - 480 (2020)
Degradation of 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphe-noxy)propane-1,3-diol (1), a model compound for lignin β-O-4 linkage was examined with iron, ruthenium, rhodium and iridium complexes bearing cyclopentadienone ligand. Cyclopentadienone iron complex gave only a small amount of degraded product with reduced molecular weight. Cyclopentadienone ruthenium complex, so called Shvo's catalyst, afforded 3,4-dimethoxybenzaldehyde (a3) in 14.3% yield after CαCβ bond cleavage. On the other hand, cyclopentadienone group-9 metal complexes catalyzed CβO bond cleavage to afford guaiacol (b1) as a main product in up to 74.9% yield.
Oxidation of lignin model compounds by organic and transition metal-based electron transfer mediators
Rochefort, Dominic,Bourbonnais, Robert,Leech, Donal,Paice, Michael G.
, p. 1182 - 1183 (2002)
We have studied the oxidation of lignin model compounds by organic and transition metal-based mediators using either an enzyme or an electrolysis cell as the mediator oxidizing agent. Electrolysis of inorganic mediator seems a promising technology for pulp delignification.
Hydrogenolysis of a γ-Acetylated Lignin Model Compound with a Ruthenium-Xantphos Catalyst
Wu, Adam,Lauzon, Jean Michel,James, Brian R.
, p. 511 - 518 (2015)
Catalytic hydrogenolysis of a γ-acetylated dimer lignin model compound is effected using a Ru-xantphos catalyst. Mechanistic investigations show mono-aryl degradation products are generated from the β-O-4 substrate as well as a terminal alkene ketone dimer (bis-aryl) that further dimerizes to a tetra-aryl product. Preliminary results using an acetylated kraft lignin as a substrate are also discussed. Graphical Abstract: [Figure not available: see fulltext.]
Selective aerobic benzylic alcohol oxidation of lignin model compounds: Route to aryl ketones
Dawange, Monali,Galkin, Maxim V.,Samec, Joseph S. M.
, p. 401 - 404 (2015)
A mild and chemoselective oxidation of the α-alcohol in β-O-4'-ethanoaryl and β-O-4'-glycerolaryl ethers has been developed. The benzylic alcohols were selectively dehydrogenated to the corresponding ketones in 60-93-% yield. A one-pot selective route to aryl ethyl ketones was performed. The catalytic system comprises recyclable heterogeneous palladium, mild reaction conditions, green solvents, and oxygen in air as oxidant. Catalytic amounts of a coordinating polyol were found pivotal for an efficient aerobic oxidation. The ligninator: A mild and chemoselective oxidation of the α-alcohol in β-O-4' lignin model compounds is developed. The benzylic alcohols are selectively dehydrogenated to the corresponding ketones in 60-93-% yield. A one-pot selective route to aryl ethyl ketones is performed. The catalytic system comprises recyclable heterogeneous palladium, mild reaction conditions, green solvents, and oxygen in air as oxidant.
A mechanistic survey of the oxidation of alcohols and ethers with the enzyme laccase and its mediation by TEMPO
D'Acunzo, Francesca,Baiocco, Paola,Fabbrini, Maura,Galli, Carlo,Gentili, Patrizia
, p. 4195 - 4201 (2002)
The oxidation of alcohols and ethers by O2 with the enzyme laccase, mediated by the stable N-oxyl radical TEMPO, affords carbonylic products. An ionic mechanism is proposed, where a nucleophilic attack of the oxygen lone-pair of the alcohol (or ether) onto the oxoammonium form of TEMPO (generated by laccase on oxidation) takes place leading to a transient adduct. Subsequent deprotonation of this adduct a to the C-O bond leads to the carbonylic product. Additional mechanistic considerations for the laccase-mediated oxidation of ethers and thioethers are offered. The proposed mechanism is supported by: (i) investigating the inter- and intramolecular selectivity of oxidation with appropriate substrates, (ii) thermochemical considerations, and (iii) attempting a Hammett correlation for the oxidation of a series of 4-X-substituted benzyl alcohols, wherein a shift of the rate-determining step as a function of the 4-X-substituent results. Based on the above points, the lack of mediation efficiency of another stable N-oxyl radical (viz., IND-O) can be explained. Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2002.
Roles of small laccases from streptomyces in lignin degradation
Majumdar, Sudipta,Lukk, Tiit,Solbiati, Jose O.,Bauer, Stefan,Nair, Satish K.,Cronan, John E.,Gerlt, John A.
, p. 4047 - 4058 (2014)
Laccases (EC 1.10.3.2) are multicopper oxidases that can oxidize a range of substrates, including phenols, aromatic amines, and nonphenolic substrates. To investigate the involvement of the small Streptomyces laccases in lignin degradation, we generated acid-precipitable polymeric lignin obtained in the presence of wild-type Streptomyces coelicolor A3(2) (SCWT) and its laccase-less mutant (SCΔLAC) in the presence of Miscanthus x giganteus lignocellulose. The results showed that strain SCΔLAC was inefficient in degrading lignin compared to strain SCWT, thereby supporting the importance of laccase for lignin degradation by S. coelicolor A3(2). We also studied the lignin degradation activity of laccases from S. coelicolor A3(2), Streptomyces lividans TK24, Streptomyces viridosporus T7A, and Amycolatopsis sp. 75iv2 using both lignin model compounds and ethanosolv lignin. All four laccases degraded a phenolic model compound (LM-OH) but were able to oxidize a nonphenolic model compound only in the presence of redox mediators. Their activities are highest at pH 8.0 with a low krel/Kapp for LM-OH, suggesting that the enzymes' natural substrates must be different in shape or chemical nature. Crystal structures of the laccases from S. viridosporus T7A (SVLAC) and Amycolatopsis sp. 75iv2 were determined both with and without bound substrate. This is the first report of a crystal structure for any laccase bound to a nonphenolic β-O-4 lignin model compound. An additional zinc metal binding site in SVLAC was also identified. The ability to oxidize and/or rearrange ethanosolv lignin provides further evidence of the utility of laccase activity for lignin degradation and/or modification.
Iron-catalysed oxidative cleavage of lignin and β-O-4 lignin model compounds with peroxides in DMSO
Mottweiler, Jakob,Rinesch, Torsten,Besson, Claire,Buendia, Julien,Bolm, Carsten
, p. 5001 - 5008 (2015)
Simple FeCl3-derived iron catalysts are used for the cleavage of β-O-4 linkages in lignin and lignin model compounds. The degradation of the β-O-4 linkages and the resinol structures in both organosolv and kraft lignin was proven by 2D-NMR (HSQC) experiments, and the oxidative depolymerisation of these lignin sources was confirmed by GPC. Key reactive species facilitating this cleavage are methyl radicals generated from H2O2 and DMSO.
Selective route to 2-propenyl aryls directly from wood by a tandem organosolv and palladium-catalysed transfer hydrogenolysis
Galkin, Maxim V.,Samec, Joseph S.M.
, p. 2154 - 2158 (2014)
A tandem organosolv pulping and Pd-catalysed transfer hydrogenolysis depolymerisation and deoxygenation has been developed. The tandem process generated 2-methoxy-4-(prop-1-enyl)phenol in 23 % yield (92 % theoretical monomer yield) starting from pine wood and 2,6-dimethoxy-4-(prop-1-enyl)phenol in 49 % yield (92 % theoretical monomer yield) starting from birch wood. Only endogenous hydrogen from wood was consumed, and the reaction was performed using green solvents.
