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K. Dawes

Bio: K. Dawes is an academic researcher. The author has contributed to research in topics: Crotonaldehyde & Acetaldehyde. The author has an hindex of 3, co-authored 6 publications receiving 22 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the synthesis of 1,4-benzoquinones carrying side-chains is described, severally, the following sidechains: CH(OH)·CH2Ph,CD(OH),CH2P, CMe(OH,CH 2P, CH 2P), CH 2Ph, CH 1.
Abstract: The synthesis is described of 1,4-benzoquinones carrying, severally, the following side-chains: CH(OH)·CH2Ph,CD(OH)·CH2Ph, CMe(OH)·CH2Ph, CH(OH)·CHPh2, CH(OH)·CH2·CH:CH2, and CMe(OH)·CH2·CH:CH2. When irradiated with visible light all the secondary alcohols yield 2,5-dihydroxybenzaldehyde, and all the tertiary alcohols give 2,5-dihydroxyacetophenone, probably via fragmentation of the derived alkoxyl radicals. The tertiary alcohols also yield isomers in which reorganisation of the side-chain has occurred. Mechanisms are suggested.

9 citations

Journal ArticleDOI
TL;DR: The synthesis of 1,4-benzoquinones carrying sidechains [CH2]2·OH, CH2·CH(OH)Me, [CH 2]2 ·Ph, CH 2·CHPh2, [ CH 2] 2·CO2Et, CH(CO 2Et)2, cis-and trans-CHCHPh, ChCHPh 2, CHCPh2 and CO·CHCHPH 2 is described in this paper.
Abstract: The synthesis of 1,4-benzoquinones carrying, severally, the side-chains [CH2]2·OH, CH2·CH(OH)Me, [CH2]2·Ph, CH2·CHPh2, [CH2]2·CO2Et, CH2·CH(CO2Et)2, cis- and trans-CHCHPh, CHCPh2, and CO·CHCHPh is described. When irradiated with visible light the hydroxyalkylquinones yield the corresponding carbonyl compounds. The phenyl-, diphenyl-, and ethoxycarbonyl-ethylquinones and the β-phenylstyrylquinone give 2,3-dihydrobenzofurans. Mechanisms are discussed. Diethyl (1,4-benzoquinonyl)methylmalonate is essentially unchanged. The remaining quinones afford unidentified amorphous products.

9 citations

Journal ArticleDOI
TL;DR: In the presence of terephthaldehyde, p-cyanobenzaldehyde, and p-trifluoromethylbenzaldehyde, 1,4-benzoquinone yields the corresponding quinol monoaroyl esters as the major addition products.
Abstract: Irradiation of 1,4-benzoquinone with visible light in the presence of terephthaldehyde, p-cyanobenzaldehyde, and p-trifluoromethylbenzaldehyde yields the corresponding quinol monoaroyl esters as the major addition products. Similarly, naphthazarinquinone, 1,4-benzoquinone-2,3-dicarboxylic anhydride, and 2,3-dicyano-1,4-benzoquinone in acetaldehyde give the corresponding quinol monoacetates. 1,4-Benzoquinone gives quinol monoacrylate exclusively when it is irradiated in benzene containing acraldehyde, but in the presence of crotonaldehyde it yields both quinol monocrotonate and crotonylquinol. The significance of these results is discussed.

5 citations


Cited by
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Journal ArticleDOI
TL;DR: A large series of coumarin derivatives were tested for their monoamine oxidase A and B inhibitory activity, revealing the importance of lipophilic interactions in modulating the inhibition and excluding any dependence on electronic properties.
Abstract: A large series of coumarin derivatives (71 compounds) were tested for their monoamine oxidase A and B (MAO-A and MAO-B) inhibitory activity. Most of the compounds acted preferentially on MAO-B with IC(50) values in the micromolar to low-nanomolar range; high inhibitory activities toward MAO-A were also measured for sulfonic acid esters. The most active compound was 7-[(3, 4-difluorobenzyl)oxy]-3,4-dimethylcoumarin, with an IC(50) value toward MAO-B of 1.14 nM. A QSAR study of 7-X-benzyloxy meta-substituted 3,4-dimethylcoumarin derivatives acting on MAO-B yielded good statistical results (q(2)() = 0.72, r(2)() = 0.86), revealing the importance of lipophilic interactions in modulating the inhibition and excluding any dependence on electronic properties. CoMFA was performed on two data sets of MAO-A and MAO-B inhibitors. The GOLPE procedure, with variable selection criteria, was applied to improve the predictivity of the models and to facilitate the graphical interpretation of results.

260 citations

Journal ArticleDOI
TL;DR: In this paper, the quantum yields for the photosensitized production of singlet oxygen and superoxide ion by the quinones 1,4-benzoquinone, BQ, 2-methyl-1,4-, MBQ, NQ2S, AQDS in aqueous buffer (pH 7), at wavelengths above 310nm, have been determined.
Abstract: Quantum yields for the photosensitized production of singlet oxygen and superoxide ion by the several quinones 1,4-benzoquinone, BQ, 2-methyl-1,4-benzoquinone, MBQ, sodium 1,4-naphthoquinone-2-sulfonate, NQ2S, sodium 9,10-anthraquinone-2-sulfonate, AQ2S, 1,4-naphthoquinone, NQ, 2-hydroxy-1,4-naphthoquinone, LWQ, 5,8-dihydroxy-1,4-naphthoquinone, NZQ, 5-hydroxy-1,4-naphthoquinone, JQ, and disodium 9,10-anthraquinone-1,5-disulfonate, AQDS in aqueous buffer (pH 7), at wavelengths above 310 nm, have been determined. Quantum yields for the production of singlet oxygen were found to be smaller than that for the production of superoxide. The quantum yield for the production of the hydroxyl adduct of 5,5-dimethyl pyrroline-1-oxide, DMPO-OH, by NQ was also determined and was found to be oxygen-concentration-dependent while the photoproduction of this adduct by hydroxynaphthoquinones was not observed. Evidence was obtained which suggests that the observed DMPO-OH adduct is produced by the free hydroxyl radical, at least at low NQ concentration.

127 citations

Journal ArticleDOI
TL;DR: Structural-activity relationship studies indicate that the 2-methoxymethylenecyclopent-4-ene-1,3-dione structural moiety is the pharmacophore responsible for the antifungal activity of this class of compounds while the side chain styryl-like moiety plays an important complementary role, presumably contributing to target binding.
Abstract: Coruscanone A, a plant-derived cyclopentenedione derivative, showed potent in vitro antifungal activity against Candida albicans and Cryptococcus neoformans comparable to amphotericin B and fluconazole. A series of analogues have been synthesized by modification of the cyclopentenedione ring, the enolic methoxy functionality, and the side chain styryl moiety of this natural product lead. A structurally close 1,4-benzoquinone analogue was also prepared. All the compounds were examined for their in vitro activity against major opportunistic fungal pathogens including C. albicans, C. neoformans, and Aspergillus fumigatus and fluconazole-resistant C. albicans strains, with several analogues demonstrating potent antifungal activity. Structure-activity relationship studies indicate that the 2-methoxymethylenecyclopent-4-ene-1,3-dione structural moiety is the pharmacophore responsible for the antifungal activity of this class of compounds while the side chain styryl-like moiety plays an important complementary role, presumably contributing to target binding.

61 citations

Journal ArticleDOI
TL;DR: The hypothesis that the biogenesis of some methylenedioxy bridged natural products could proceed via similar nonenzymatic mechanisms is presented.

49 citations

Journal ArticleDOI
TL;DR: In this paper, the synthesis of phenanthroviridone, gilvocarcin BE-12406X2, and antibiotic WS 5995B were described, based on palladium and copper-catalyzed coupling reactions of sterically hindered arylstannanes with 2-bromonaphthoquinones.

39 citations