- Synthesis of isoxazole derivatives of 4,5-dihydro-1H-pyrazole
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Cyclocondensation of pent-1-en-4-yn-3-one with phenylhydrazine and p-tolylhydrazine occurs at the positions 1, 3. Proceeding from the 1-aryl-3-ethynyl-4,5-dihydro-1H-pyrazoles formed in the reaction in yields up to 95% we prepared potentially biologically
- Golovanov,Odin,Vologzhanina,Voronova,Anoshina,Bekin
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- Tetravinylallene
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The first chemical synthesis of tetravinylallene (3,5-divinylhepta-1,3,4,6-tetraene) is reported. The final, key step of the synthesis involves a palladium-catalyzed, Negishi-type cross-coupling involving 1,5-transposition of a penta-2-en-4-yn-1-ol methanesulfonate. The unprecedented fundamental hydrocarbon is sufficiently stable to be purified by flash chromatography. A similar synthetic pathway grants access to the first substituted tetravinylallenes, which provide insights into the influence of substitution upon stability and reactivity. Tetravinylallenes are shown to break new ground in swift structural complexity creation, with three novel sequences reported.
- Elgindy, Cecile,Ward, Jas S.,Sherburn, Michael S.
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- Quantitative studies and sensory analyses on the influence of cultivar, spatial tissue distribution, and industrial processing on the bitter off-taste of carrots (Daucus carota L.) and carrot products
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Although various reports pointed to 6-methoxymellein (1) as a key player imparting the bitter taste in carrots, activity-guided fractionation experiments recently gave evidence that not this isocoumarin but bisacetylenic oxylipins contribute mainly to the off-taste. Among these, (Z)-heptadeca-1,9-dien-4,6- diyn-3-ol (2), (Z)-3-acetoxy-heptadeca-1,9-dien-4,6-diyn-8-ol (3), and (Z)-heptadeca-1,9-dien-4,6-diyn-3,8-diol (falcarindiol, 4) have been successfully identified. In the present study, an analytical procedure was developed enabling an accurate quantitation of 1-4 in carrots and carrot products. To achieve this, (E)-heptadeca-1,9-dien-4,6-diyn-3,8-diol was synthesized as a suitable internal standard for the quantitative analysis of the bisacetylenes. On the basis of taste activity values, calculated as the ratio of the concentration and the human sensory threshold of a compound, a close relationship between the concentration of 4 and the intensity of the bitter off-taste in carrots, carrot puree, and carrot juice was demonstrated, thus showing that compound 4 might offer a new analytical measure for an objective evaluation of the quality of carrot products. Quantitative analysis on the intermediate products in industrial carrot processing revealed that removing the peel as well as green parts successfully decreased the concentrations in the final carrot puree by more than 50%.
- Czepa, Andreas,Hofmann, Thomas
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- Structures, biological activities, and total syntheses of 13-hydroxy- and 13-acetoxy-14-nordehydrocacalohastine, novel modified furanoeremophilane-type sesquiterpenes from Trichilia cuneata
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(Chemical Equation Presented) 13-Hydroxy-14-nordehydrocacalohastine (2) and 13-acetoxy-14-nordehydrocacalohastine (3), two novel modified furanoeremophilane-type sesquiterpenes isolated from Trichilia cuneata, showed inhibitory activities for membrane lip
- Doe, Matsumi,Shibue, Taku,Haraguchi, Hiroyuki,Morimoto, Yoshiki
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p. 1765 - 1768
(2007/10/03)
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- Synthesis and cytotoxic activity of a series of diacetylenic compounds related to falcarindiol
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The synthesis of a series of diacetylenic compounds related to the natural product falcarindiol has been carried out. Unsymmetrical diacetylenes were prepared by a modification of the Cadiot-Chodkiewicz coupling reaction, while a Glaser coupling was used to prepare symmetrical diacetylenes. These compounds have been tested for in vitro cytotoxic activity against Hep-G2, and H-4-II-E cell lines. Diacetylenes with additional unsaturation at C-1, 2, appended with hydroxyl groups at C-3 and C-8, or with long hydrophobic chains, exhibited IC50 values in the micromolar range.
- Setzer,Gu,Wells,Setzer,Moriarity
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p. 1776 - 1777
(2007/10/03)
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- Stereoselective synthesis of β-ketoesters from prop-2-yn-1-ols
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The activation of allylic prop-2-yn-1-ols by the [Ru(μ-O2CH)(CO)2(PPh3)]2 catalyst in the presence of carboxylic acids leads to unsaturated β-ketoesters in one step. The utilization of optically active prop-2-yn-1-ols provides a new stereoselective access to optically active β-ketoesters with retention of configuration at the propargylic carbon.
- Darcel, Christophe,Bruneau, Christian,Dixneuf, Pierre H.,Roberts, Stanley M.
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p. 9241 - 9252
(2007/10/03)
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- Convenient synthesis of 4-methylene-2-oxazolidinones and 4-methylenetetrahydro-1,3-oxazin-2-ones via transition-metal catalyzed intramolecular addition of nitrogen atom to actylenic triple bond
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2-Propynyl tosylcarbamates 1 undergo cyclization smoothly by the catalysis of CuCl/Et3N or AgNCO/Et3N to furnish 4-methylene-2-oxazolidinones 2 in good yields. The similar cyclization of the N-acyl derivatives of 1 (PhCO, MeCO, EtOCO, etc.) is catalyzed effectively by AgNCO/t-BuOK. These reactions accommodate a variety of substituents at C1 and C3 of 2-propyn-1-ol and provide (Z)-2 as single stereoisomers. The scope of the cyclization of 3-butynyl carbamates is rather limited, and in general only N-tosyl derivatives of terminally unsubstituted 3-butyn-1-ols undergo cyclization to give 4-methylenetetrahydro-1,3-oxazin-2-ones in synthetically useful yields by the catalysis of AgNCO/Et3N or AgNCO/t-BuOK.
- Tamaru,Kimura,Tanaka,Kure,Yoshida
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p. 2838 - 2849
(2007/10/02)
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