4857-70-9Relevant academic research and scientific papers
Copper-promoted overall transformation of 4-tert-butylphenol to its para-hydroxyquinonic derivative, 2-hyroxy-5-tert-butyl-1,4-benzoquinone. Biomimetic studies on the generation of Topaquinone in copper amine oxidases
Rinaldi, Andrea C.,Ponticelli, Gustavo,Oliva, Stefania,Di Giulio, Antonio,Sanjust, Enrico
, p. 989 - 992 (2000)
Topaquinone (TPQ) is a cofactor present at the active site of copper amine oxidases, derived from a Tyr residue inserted in the polypeptide chain through a copper-dependent but otherwise largely unknown mechanism. A simple model system was developed that permits to obtain the overall transformation of 4-tert-butylphenol, chosen as a model for Tyr, into a TPQ-like, para-hydroxyquinonic structure in the presence of Cu(II)-imidazole mononuclear complexes. (C) 2000 Elsevier Science Ltd. All rights reserved.
A divergent and selective synthesis of ortho- and para-quinones from phenols
Huang, Zheng,Kwon, Ohhyeon,Esguerra, Kenneth Virgel N.,Lumb, Jean-Philip
, p. 5871 - 5885 (2015/08/04)
Abstract We describe a divergent synthesis of substituted ortho- and para-quinones by catalytic aerobic oxygenation of phenols. Substituted quinones are omnipresent in chemistry and biology, but their synthesis frequently suffers from low efficiency and poor scope. Our methodology employs a catalytic aerobic di-functionalization of phenols to aryloxy-ortho-quinones. Regioselective substitution with an alcohol provides the alkoxy substituted ortho- or para-quinone, while hydrolysis affords the para-hydroxyquinone. These are mild and selective conditions for the synthesis of diversely substituted quinones from readily available phenol starting materials.
A biomimetic catalytic aerobic functionalization of phenols
Esguerra, Kenneth Virgel N.,Fall, Yacoub,Lumb, Jean-Philip
supporting information, p. 5877 - 5881 (2014/06/10)
The importance of aromatic C-O, C-N, and C-S bonds necessitates increasingly efficient strategies for their formation. Herein, we report a biomimetic approach that converts phenolic C-H bonds into C-O, C-N, and C-S bonds at the sole expense of reducing dioxygen (O2) to water (H 2O). Our method hinges on a regio- and chemoselective copper-catalyzed aerobic oxygenation to provide ortho-quinones. ortho-Quinones are versatile intermediates, whose direct catalytic aerobic synthesis from phenols enables a mild and efficient means of synthesizing polyfunctional aromatic rings. The direct approach: Polyfunctional aromatic rings have been generated by direct functionalization of C-H bonds to C-O, C-N, and C-S bonds at the sole expense of reducing O2 to H2O. The method hinges on a regio- and chemoselective, copper-catalyzed aerobic oxygenation of phenols to provide ortho-quinones (see scheme), thus mimicking the ubiquitous biosynthetic pathway of melanogenesis.
Chemoselective organocatalytic aerobic oxidation of primary amines to secondary imines
Wendlandt, Alison E.,Stahl, Shannon S.
supporting information; experimental part, p. 2850 - 2853 (2012/07/17)
Biomimetic aerobic oxidation of primary benzylic amines has been achieved by using a quinone catalyst. Excellent selectivity is observed for primary, unbranched benzylic amines relative to secondary/tertiary amines, branched benzylic amines, and aliphatic amines. The exquisite selectivity for benzylic amines enables oxidative self-sorting within dynamic mixtures of amines and imines to afford high yields of cross-coupled imine products.
Mechanism-based cofactor derivatization of a copper amine oxidase by a branched primary amine recruits the oxidase activity of the enzyme to turn inactivator into substrate
Qiao, Chunhua,Ling, Ke-Qing,Shepard, Eric M.,Dooley, David M.,Sayre, Lawrence M.
, p. 6206 - 6219 (2007/10/03)
The copper amine oxidases (CAOs) have evolved to catalyze oxidative deamination of unbranched primary amines to aldehydes. We report that a branched primary amine bearing an aromatization-prone moiety, ethyl 4-amino-4,5- dihydrothiophene-2-carboxylate (1), is recognized enantioselectively (S ? R) by bovine plasma amine oxidase (BPAO) both as a temporary inactivator and as a substrate. Substrate activity results from an O2-dependent turnover of the covalently modified enzyme, with release of 4-aminothiophene-2- carboxylate (2) as ultimate product. Interaction of (S)-1 with BPAO occurs within the enzyme active site with a dissociation constant of 0.76 μM. Evidence from kinetic and spectroscopic studies, and HPLC analysis of stoichiometric reactions of BPAO with (S)-1, combined with a model study using a quinone cofactor mimic, establishes that the enzyme metabolizes 1 according to a transamination mechanism. Following the initial isomerization of substrate Schiff base to product Schiff base, a facile aromatization of the latter results in a metastable N-aryl derivative of the reduced cofactor aminoresorcinol, which is catalytically inactive. The latter derivative is then slowly oxidized by O2, apparently facilitated partially by the active-site Cu(II), to form a quinonimine of the native cofactor that releases 2 upon hydrolysis or transimination with substrate amine. Preferential metabolism of (S)-1 is consistent with the preferential removal of the pro-S α-proton in metabolism of benzylamine by BPAO. This study represents the first report of product identification in metabolism of a branched primary amine by a copper amine oxidase and suggests a novel type of reversible mechanism-based (covalent) inhibition where inhibition lifetime can be fine-tuned independently of inhibition potency.
Copper(II)-mediated autoxidation of tert-butylresorcinols
Ling, Ke-Qing,Lee, Younghee,Macikenas, Dainius,Protasiewicz, John D.,Sayre, Lawrence M.
, p. 1358 - 1366 (2007/10/03)
Although copper(II)-mediated oxidation of phenols results in oxidative coupling rather than in oxygenation, it was recently reported that naturally occurring 5-alkylresorcinols undergo oxygenation in the presence of copper(II). To explore the generality of this reaction, the copper(II)-mediated autoxidation of 4-tert-butylresorcinol and 4,6-di-tert-butylresorcinol was investigated and was found to result in direct oxygenation at open activated positions and, at the tert-butyl-substituted positions, in oxygenation with competing loss of (as isobutylene) and 1,2-rearrangement of the tert-butyl group. 5-tert-Butyl-2-hydroxy-1,4-benzoquinone is the major product from both starting materials, and the final product mixture reflects, in part, coupling of metastable initially formed electrophilic and nucleophilic side products. Mechanisms that are consistent with the observed products and control reactions are proposed. The key step appears to be equilibration of a copper(II)-resorcinolate with a charge-transfer radical form that reacts regioselectively with O2 as prescribed by resonance.
Temporary inactivation of plasma amine oxidase by alkylhydrazines. A combined enzyme/model study implicates cofactor reduction/reoxidation but cofactor deoxygenation and subsequent reoxygenation in the case of hydrazine itself
Lee,Jeon,Huang,Sayre
, p. 1925 - 1937 (2007/10/03)
It has been known for some time that hydrazine and its methyl and 1,1-dimethyl analogues induce inactivation of the copper-containing quinone-dependent plasma amine oxidase but that the activity recovers over time, suggesting metabolism of all three inhib
Model studies of topaquinone-dependent amine oxidases. 1. Oxidation of benzylamine by topaquinone analogs
Mure, Minae,Klinman, Judith P.
, p. 8698 - 8706 (2007/10/02)
The aerobic oxidation of benzylamine by model compounds of topaquinone, the active site organic cofactor in copper-containing amine oxidases, was studied in order to elucidate the chemical function of the cofactor in substrate oxidation. In this study, topaquinone hydantoin (1(ox)) and a series of 2-hydroxy-5-alkyl-1,4-benzoquinones which differ in the bulk of their alkyl substituent (5, 6, 7, and 8) were employed as model compounds of the cofactor. The p-quinones (9, 10, 11, and 12) and the o-quinone (13 and 14) were prepared in order to compare them to the topaquinone analogs. Benzylamine was oxidized by the topaquinone analogs (1(ox), 5, 6, 7, and 8) to yield N-benzylidenebenzylamine (PhCH = NCH2Ph) as a sole product in acetonitrile at room temperature. The quinones bearing a bulky substituent (1(ox), 5, and 6) were found to be more efficient catalysts than those bearing a small primary alkyl group (7 and 8). In the latter case, the dimers (16 and 17) of the substrate Schiff base intermediates (15, R = methyl, ethyl) were isolated. The p-quinones (9, 10, 11, and 12) were catalytically inactive. The o-quinones (13 and 14) had detectable catalytic activity at room temperature. In anaerobic reactions of the o-quinones (13 and 14) with benzylamine, quantitative formation of the product (PhCH = NCH2Ph) was observed. For both o-quinones, products and intermediates which support a transamination mechanism were identified by 1H NMR spectroscopy. The order of reactivity of quinones (5 > 14 > 13) reflects their redox potentials, such that regeneration of quinone may be rate-determining with o-quinones. These results demonstrate a substantial role of the 2-hydroxyl group of the topaquinone in preventing the formation of Michael adducts with substrate amine and in facilitating the reoxidation of aminoresorcinol intermediates.
The Reactions of Lignin with Alkaline Hydrogen Peroxide. Part IV. Products from the Oxidation of Quinone Model Compounds
Gellerstedt, Goeran,Hardell, Hanne-Lise,Lindfors, Eva-Lisa
, p. 669 - 674 (2007/10/02)
Simple para- and orhto-quinoid structures related to lignin have been oxidized with hydrogen peroxide under mild alkaline conditions.Most of the reaction products, i.e. carboxylic acids formed by oxidative cleavage of the quinoid ring together with acids formed by more extensive degradation of the starting materials, were identified after conversion into esters.In addition, small amounts of hydroxylated quinones were found.Mechanisms for the formation of these products are suggested and the significance of the results for the bleaching of mechanical pulps with hydrogen peroxide is briefly discussed.
