617-48-1Relevant articles and documents
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Yoshida et al.
, (1952)
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Cyanide as a primordial reductant enables a protometabolic reductive glyoxylate pathway
Krishnamurthy, Ramanarayanan,Pulletikurti, Sunil,Yadav, Mahipal,Yerabolu, Jayasudhan R.
, p. 170 - 178 (2022/02/11)
Investigation of prebiotic metabolic pathways is predominantly based on abiotically replicating the reductive citric acid cycle. While attractive from a parsimony point of view, attempts using metal/mineral-mediated reductions have produced complex mixtures with inefficient and uncontrolled reactions. Here we show that cyanide acts as a mild and efficient reducing agent mediating abiotic transformations of tricarboxylic acid intermediates and derivatives. The hydrolysis of the cyanide adducts followed by their decarboxylation enables the reduction of oxaloacetate to malate and of fumarate to succinate, whereas pyruvate and α-ketoglutarate themselves are not reduced. In the presence of glyoxylate, malonate and malononitrile, alternative pathways emerge that bypass the challenging reductive carboxylation steps to produce metabolic intermediates and compounds found in meteorites. These results suggest a simpler prebiotic forerunner of today’s metabolism, involving a reductive glyoxylate pathway without oxaloacetate and α-ketoglutarate—implying that the extant metabolic reductive carboxylation chemistries are an evolutionary invention mediated by complex metalloproteins. [Figure not available: see fulltext.].
Directly Microwave-Accelerated Cleavage of C?C and C?O Bonds of Lignin by Copper Oxide and H2O2
Qu, Chen,Ito, Keigo,Katsuyama, Isamu,Mitani, Tomohiko,Kashimura, Keiichiro,Watanabe, Takashi
, p. 4510 - 4518 (2020/05/18)
Model erythro, phenolic, and nonphenolic lignin β-O-4 dimer compounds are treated with copper oxide and H2O2 at the electronic field maximum position of a single-mode 2.45 GHz microwave system equipped with a cavity resonator. The products obtained through microwave heating and oil-bath heating with the same reaction vessel and temperature profile are quantitatively compared. Dimer degradation is found to proceed through consecutive elementary reactions. The phenolic dimer is dehydroxylated and this is followed by the spontaneous cleavage of Cα?Cβ and C?O?C bonds to produce guaiacol, vanillin, and vanillic acid. The reaction of the nonphenolic dimer produces veratric acid, veratraldehyde, and guaiacol. Microwave irradiation accelerates cleavage of the side chain and the oxidation of vanillin to vanillic acid. However, no acceleration of veratraldehyde oxidation to veratric acid or aromatic ring cleavage to produce dicarboxylic acids is observed. The selective acceleration of elementary reactions during the degradation of model lignin compounds indicates that microwaves interact with reaction intermediates that are sensitive to electromagnetic waves.
Catalytic transfer hydrogenation of maleic acid with stoichiometric amounts of formic acid in aqueous phase: Paving the way for more sustainable succinic acid production
López Granados,Moreno,Alba-Rubio,Iglesias,Martín Alonso,Mariscal
supporting information, p. 1859 - 1872 (2020/04/07)
The aqueous phase hydrogenation of maleic acid (MAc) to succinic acid (SAc) is demonstrated in the absence of any organic solvent and using stoichiometric amount of formic acid (FAc) as source of H2. Among the different noble metals (Pd, Au, Ru, Pt and Rh) and supports investigated (γ-Al2O3, TiO2, CeO2, ZrO2, WO3, CeZrO4, carbon, nicanite, SiO2 and TS-1), Pd/C was identified as the best catalyst. We observe that the undesirable formation of malic acid (MalAc) by hydration of MAc must be prevented. The transformation of MAc to SAc with negligible formation of MalAc is possible by using relatively mild temperature (140-150 °C) and a high catalyst to MAc ratio (i.e. fixed bed continuous flow reactor). Using the carboxylate forms (disodium maleate and sodium formate) instead of the acids results in an increase of the reaction rate. In a fixed bed reactor under a continuous flow of 15 wt% of MAc at a WHSV = 12 h-1 (contact time = 5 min), at 150 °C, 10 bar of N2 and using a formic acid/maleic acid molar ratio = 1, a yield of SAc close to 98% was obtained, equivalent to a productivity of 1.87 g SAc per gcat per·h. Leaching of Pd was below 0.02 ppm. No deactivation was observed in long term experiments at 150 °C (ca. 730 h), although the characterization of the used catalyst by CO chemisorption and TEM and XPS studies showed certain sintering of Pd particles. Regarding the mechanism of the reaction, kinetic isotopic experiments using deuterated DCOOH indicated that the reaction must essentially proceed via catalytic transfer hydrogenation, formyl H of formic acid is involved in the rate determining step of the reaction. When using maleate and formate sodium salts, the second H needed for the reaction is supplied by the solvent (H2O molecules). A preliminary environmental assessment (Life Cycle Analysis, LCA) of this CTH approach indicates that for relevant environmental categories of the LCA (such as climate change and consumption of fossil resources) the CTH process is greener than conventional hydrogenation process; the benefits are even larger if biomass-derived FAc is involved.