Model Quinone Research Articles

Reactions of ß-ARYL Lignin Model Quinone Methides with Anthrahydroquinone and Anthranol

Abstract Quinone methides prepared in situ from phenylcoumaran and s-C-l lignin models which did not contain a s-hydroxymethyl group, readily formed addition products with anthranol but not with anthrahydroquinone. For s-aryl lignin models containing the hydroxymethyl group, the retro-aldol reaction (liberating formaldehyde) was so facile under the conditions used that stilbene formation from the quinone methide took precedence over adduct formation.

The contribution of alkylation to the activity of quinone antitumor agents.

Studies have shown that the quinone group can produce tumor cell kill by a mechanism involving active oxygen species. This cytotoxic activity can be correlated with the induction of DNA double strand breaks and is enhanced by the ability of the quinone compound to bind to DNA by alkylation. The cytotoxic activity and the production of DNA damage by model quinone antitumor agents were compared in L5178Y cells, sensitive and resistant to alkylating agents, to assess the contribution of alkylation to the activity of these agents. The resistant L5178Y/HN2 cells were found to be two fold and six fold more resistant to the alkylating quinones, benzoquinone mustard and benzoquinone dimustard, respectively, than parent L5178Y cells. In contrast, the L5178Y/HN2 cells showed no resistance to the nonalkylating quinones, hydrolyzed benzoquinone mustard and bis(dimethylamino)benzoquinone. The alkylating quinones produced approximately two fold less cross-linking in L5178Y/HN2 cells compared with L5178Y sensitive cells. DNA double strand break formation by hydrolyzed benzoquinone mustard and bis(dimethylamino)benzoquinone was not significantly different in sensitive and resistant cells. However, the induction of double strand breaks by the alkylating quinones benzoquinone mustard and benzoquinone dimustard was reduced by 5-fold and 15-fold, respectively, in L5178Y/HN2 cells. These results show that the alkylating activity of the alkylating quinones cannot directly explain all of the enhanced cytotoxic activity of these agents. Furthermore, they provide strong evidence that the enhanced formation of DNA double strand breaks by alkylating quinone agents is directly related to the ability of these agents to bind to DNA. This increased formation of strand breaks may account for the enhanced cytotoxic activity of the alkylating quinones.

ChemInform Abstract: Stereochemistry of Adduct Formation Between a Lignin Model Quinone Methide and Anthrone, 10‐Methylanthrone and 10‐Phenylanthrone.

AbstractThe anthrones (III) react with the quinone methide (II) derived from a phenolic lignin model compound (I) under known conditions to form adducts (IVa) + (IVb), (IVc) + (IVd), or (IVe) similar to those believed to be intermediates in anthraquinone accelerated delignification reactions.

Adducts of Anthrahydroquinone and Anthranol with Lignin Model Quinone Methides. 9,10-13C Labelled Anthranol-Lignin Aeducts; Examination of Adouct Formation and Stereochemistry in the Polymer

Abstract Threo and erythro isomers of 3-acetoxy-1-(4-acetoxy-3-methoxyphenyl) -1- (9,10-dihydro-10-hydroxy-9-oxoanthracen-10-yl) -2-(2-tnethoxyphenoxy)-propane 8 have been synthesized. These compounds are appropriate model compounds for adducts between anthranol (9-hydroxyanthracene) and quinone raethides of β-aryl ether units in the lignin polymer. Adducts of this type are believed to result from side reactions during the anthraquinone-accelerated pulping of wood and may contribute to extensive losses of anthraquinone from the pulping system. The 13C NMR chemical shift3 of C-10 in the threo and erythro isomers of β are 44.1 and 47.5 ppm relative to tetramethylsilane. Peaks with corresponding chemical shifts appeared in a spectrum of an acetylated adduct prepared from lignin and 9,10- 3C labelled anthranol. As in model systems the threo isomer predominated.

The Stereochemistry of Adduct Formation between a Lignin Model Quinone Methide and Anthrone, 10-Methylanthrone and 10-Phenylanthrone.

The Stereochemistry of Adduct Formation between a Lignin Model Quinone Methide and Anthrone, 10-Methylanthrone and 10-Phenylanthrone.

Structure of the quinone antibiotic EM5519 and the behavior of quinones in fast atom bombardment mass spectrometry.

Fast atom bombardment (FAB) mass and MS/MS spectra of a novel quinone antibiotic are presented. Their interpretation is based upon the examination of reductive behavior of model quinones in FAB solvents.

Adducts of anthrahydroquinone and anthranol with lignin model quinone methides. 4. Proton NMR hindered rotation studies. Correlation between solution conformations and x-ray crystal structure

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdducts of anthrahydroquinone and anthranol with lignin model quinone methides. 4. Proton NMR hindered rotation studies. Correlation between solution conformations and x-ray crystal structureJohn Ralph, Lawrence L. Landucci, Brian K. Nicholson, and Alistair L. WilkinsCite this: J. Org. Chem. 1984, 49, 18, 3337–3340Publication Date (Print):September 1, 1984Publication History Published online1 May 2002Published inissue 1 September 1984https://doi.org/10.1021/jo00192a016RIGHTS & PERMISSIONSArticle Views70Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

The cationic plastoquinone radical of the chloroplast water splitting complex: Hyperfine splitting from a single methyl group determines the EPR spectral shape of Signal II

The proposal that EPR Signal II in spinach chloroplasts is due to a plastoquinone cation radical (O'Malley, P.J. and Babcock, G.T. (1983) Biophys. J. 41, 315a) has been investigated in further detail. The similarity in spectral shape between Signal II and the 2-methyl-5-isopropylhydroquinone cation radical is shown to arise from hyperfine coupling to one methyl group for both radicals. A well-resolved four line EPR spectrum of approximate relative intensity 1:3:3:1 for membrane orientation parallel and perpendicular to the applied magnetic field direction also indicates that the partially resolved structure of Signal II is due to hyperfine interaction with one methyl group, i.e., the 2-CH 3 group of the plastoquinone cation radical. The ENDOR band observed for this coupling is similar to that observed for methyl group bands of model quinone radicals. The principal hyperfine tensor values obtained for the methyl group interactions are A ⊥ = 27.2 MHz and A  = 31.4 MHz . The large isotropic coupling value (28.6 MHz) of the plastoquinone cation radical's 2-methyl group in vivo indicates that the antisymmetric orbital is the sole contributor to the spin-density distribution of Signal II. The orientation data also suggest that the plastoquinone cation radical is oriented such that the C-CH 3 bond direction, and hence the aromatic ring plane, lies perpendicular to the membrane plane.

Adducts of anthrahydroquinone and anthranol with lignin model quinone methides. 3. Independent synthesis of threo and erythro isomers

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdducts of anthrahydroquinone and anthranol with lignin model quinone methides. 3. Independent synthesis of threo and erythro isomersJohn Ralph and Lawrence L. LanducciCite this: J. Org. Chem. 1983, 48, 22, 3884–3889Publication Date (Print):November 1, 1983Publication History Published online1 May 2002Published inissue 1 November 1983https://doi.org/10.1021/jo00170a003RIGHTS & PERMISSIONSArticle Views240Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (747 KB) Get e-Alerts Get e-Alerts

Adducts of anthrahydroquinone and anthranol with lignin model quinone methides. 2. Dehydration derivatives. Proof of threo configuration

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdducts of anthrahydroquinone and anthranol with lignin model quinone methides. 2. Dehydration derivatives. Proof of threo configurationJohn Ralph and Lawrence L. LanducciCite this: J. Org. Chem. 1983, 48, 3, 372–376Publication Date (Print):February 1, 1983Publication History Published online1 May 2002Published inissue 1 February 1983https://doi.org/10.1021/jo00151a018RIGHTS & PERMISSIONSArticle Views100Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (569 KB) Get e-Alerts Get e-Alerts

Determination of the Conformation and Isomeric Composition of Lignin Model Quinone Methides By NMR

Abstract Proton and 13C NMR of representative guaiacyl and syringyl β-aryl ether quinone methides have shown that guaiacyl quinone methides, generated from the corresponding benzyl bromides, exist as isomeric pairs in approximately a 70:30 ratio, the major isomer having the 3-methoxyl group syn with respect to the side chain. The ring protons at the 2- and 6-positions in the syn-and the anti-isomera respectively are markedly deshielded by 3teric compression effects; concomitant shielding of these ring carbons is observed in the C-13 NMR. Nuclear Overhauser enhancement experiments define the major solution conformation of these species, the conformation being consistent with the observed predominance of threo-products resulting from nucleophilic addition reactions.

Adducts of anthrahydroquinone and anthranol with lignin model quinone methides. 1. Synthesis and characterization

Adducts of anthrahydroquinone and anthranol with lignin model quinone methides. 1. Synthesis and characterization

Synthesis, redox characteristics, and in vitro norepinephrine uptake inhibiting properties of 2-(2-mercapto-4,5-dihydroxyphenyl)ethylamine (6-mercaptodopamine).

In an attempt to further characterize the structural features of 6-hydroxydopamine analogues that are associated with in vivo neuronal degeneration, the synthesis of 6-mercaptodopamine was undertaken. Although reaction conditions leading to the 1,4 addition of thiols to the model quinone 4-methyl-o-benzoquinone were achieved, attempts to obtain 6-thiolated dopamine analogues by this route failed. The synthesis of 6-mercaptodopamine was achieved by the regioselective thiocyanation of O,O-dimethyldopamine, followed by bis-O-demethylation and reductive cleavage of the S-cyano group. Unlike 6-hydroxydopamine, 6-mercaptodopamine was resistant to autoxidation at pH 7.4. Cyclic voltammometric analysis, however, indicated that electrochemically generated oxidation species of 6-mercaptodopamine are unstable and undergo spontaneous reaction, presumably intramolecular cyclization. In vivo tests revealed that 6-mercaptodopamine inhibits the uptake of tritium-labeled norepinephrine by isolated rat heart atria, although to a much lesser extent than 6-hydroxydopamine.

The role of 2,4,5-trihydroxyphenylalanine in melanin biosynthesis.

Both 3,4-dihydroxyphenylalanine and 2,4,5-trihydroxyphenylalanine were oxidized with periodate and mushroom tyrosinase to determine whether the latter compound is an intermediate in melanin biosynthesis. Matrix analysis of the spectra obtained with a rapid scan spectrophotometer and comparison of the spectra of quinone intermediates with model quinones disclosed that, although 2,4,5-trihydroxyphenylalanine can be oxidized to 2-carboxy-2,3-dihydroindole-5,6-quinone (dopachrome), this oxidation proceeds through a stable intermediate, 5-(2-carboxy-2-aminoethyl)-2-hydroxy-1,4-benzoquinone, which does not appear in the oxidation of 3,4-dihydroxyphenylalanine to dopachrome. Thus, these studies are in agreement with the original postulate, that 4-(2-carboxy-2-aminoethyl)-1,2-benzoquinone and leukodopachrome are the intermediates in the major pathway for dopachrome synthesis.

Electrochemical studies of the redox behavior of α-tocopherylquinone and a related model quinone

The electrochemical reduction of α-tocopherylquinone and the model quinone, 2,3,5-trimethyl-6-(3′-methyl-3′-hydroxybutyl)quinone, has been studied in an aprotic, nonaqueous solvent. In the absence of a proton donor, the quinones, Q, are reduced reversibly in two one-electron steps to the dianion, Q 2−. Addition of ethyl malonate to the system causes protonation of the dianion and the formation of QH −. In the presence of a stronger proton donor (benzenethiol) protonation of the intermediate anion radical (Q −) gives QH ·, which is more readily reduced than the quinone. The final product of the reduction is the corresponding hydroquinone. Dual pathways of reduction are noted when HClO 4 is added to the system. In addition to causing the two-electron reduction of protonated quinone to the hydroquinone, the acid also facilitates the recyclization of the quinone and the subsequent dehydration of the electroinactive, hemiketal intermediate. The carbonium ion which results from these processes is reduced to the chromanol in a two-electron process at a potential less cathodic than the reduction of the protonated quinone. No evidence could be found to suggest that the chromanol is a reduction product when the quinone is the electroactive species.

Détermination quantitative de groupements quinoniques. Application a une serie de quinones et a un extrait pyridinique de houille

Reductive acetylation has been investigated for the purpose of developing a suitable chemical method for the quantitative determination of quinone groupings in coal extracts. The reaction has been carried out successfully from an analytical point of view on a series of model quinones, either using zinc and acetic anhydride as the reagent, or copper and hydrogen sulphide, followed by acetic anhydride. However, the procedure with zinc failed to give satisfactory results when applied to a pyridine extract of vitrinite, on account of side reactions with nitrogenous groupings in the coal structure, and spurious hydrogenolysis of carbonoxygen bonds due to non‐aprotic conditions. These difficulties were avoided in the reduction with copper. Hence, it was possible to determine that the pyridine extract of a vitrinite having a carbon content of 84.3% contained 0.95% of quinone oxygen. This value represents barely 15% of the total oxygen present in the investigated extract. The sum of hydroxyl and quinone oxygen in the extract represents 60% of the total oxygen. The remainder is thought to be largely in the form of ethers.

Protein Binding of Model Quinone Imides: II. THE INTERACTION OF SOME o-QUINONE IMIDES WITH CRYSTALLINE BOVINE SERUM ALBUMIN

Protein Binding of Model Quinone Imides: II. THE INTERACTION OF SOME o-QUINONE IMIDES WITH CRYSTALLINE BOVINE SERUM ALBUMIN

Protein Binding of Model Quinone Imides. I. The Synthesis of Some Fluorenoquinone Imides1

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTProtein Binding of Model Quinone Imides. I. The Synthesis of Some Fluorenoquinone Imides1H. R. Gutmann, J. G. Burtle, and H. T. NagasawaCite this: J. Am. Chem. Soc. 1958, 80, 20, 5551–5555Publication Date (Print):October 1, 1958Publication History Published online1 May 2002Published inissue 1 October 1958https://doi.org/10.1021/ja01553a059RIGHTS & PERMISSIONSArticle Views39Altmetric-Citations3LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (734 KB) Get e-Alerts Get e-Alerts