- Synthetic Microbial Chemistry, XXVI. - Absolute Configuration of (+)-Xanthocidin as Determined by the Synthesis of Its Enantiomers of Known Stereochemistry
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The absolute configuration of the antibiotic (+)-xanthocidin (4,5-dihydroxy-5-isopropyl-4-methyl-2-methylene-3-oxocyclopentane-1-carboxylic acid, 1) was shown to be 1R,4S,5S by the synthesis of its enantiomers.Lipase AK (Amano) was used for the key resolution step, and the absolute configuration of the resolved intermediate (+)-16 was determined by X-ray analysis of its (1S)-camphanic ester (+)-20. - Key Words: Antibiotics / Asymmetric acylation / Lipases / Streptomyces xanthocidicus / Xanthocidin
- Mori, Kenji,Horinaka, Akio,Kido, Masaru
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p. 817 - 826
(2007/10/02)
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- MAIN GROUP METAL CHEMISTRY. REACTION OF 3,3-DIALKYL-1-BROMOALLENES WITH ALUMINIUM, ZINC, AND MAGNESIUM REAGENTS
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The reactions between 1-bromo-3-methyl-1,2-pentadiene and isobutyl compounds of main group metals (Al, Zn, Mg) provide reduction, elimination, and alkylation products with chemo- and regioselectivity depending on the nature of the organometallic reagent.
- Caporusso, Anna Maria,Lardicci, Luciano,Settimo, Federico da
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p. 599 - 602
(2007/10/02)
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- Metal Catalysis in Organic Reactions. Part 13. The Reaction of 3-En-1-ynes with Trialkylalanes: Influence of Transition-metal Complexes
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The reaction between trialkylalanes and 3-alkyl-, or 4-alkyl-, or 3,4-dialkyl-but-3-en-1-ynes (1) lead to products which correspond to metallation, reduction, and carbalumination processes.The extent of such reactions, and the regio- and stereo-selectivity of the carbalumination, are dependent on the enyne used.A mechanism is proposed involving tautomeric equilibria among several α-unsaturated organoaluminium intermediates to explain the formation of the carbalumination products. In the presence of catalytic amounts of nickel and manganese complexes, 3-en-1-ynes (1), by reacting with tri-isobutylaluminium, are dimerized selectively in a 'head-to-tail' fashion to conjugated tetraenes having different structures in relation to the different nature of the transition-metal complex.The preparative aspect of these induced reactions is discussed, and, in the light of previous reports, some mechanistic considerations are presented.
- Caporusso, Anna Maria,Giacomelly, Giampaolo,Lardicci, Luciano
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p. 1900 - 1908
(2007/10/02)
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