- Precursors to damascenone: Synthesis and hydrolysis of isomeric 3,9-dihydroxymegastigma-4,6,7-trienes
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A series of four isomeric 3,9-dihydroxymegastigma-4,6,7-trienes, 8, has been prepared. The (3S,6R,9S) isomer of 8 proved to be identical to an isomer of this compound tentatively identified as an intermediate in the formation of damascenone from an allene triol. Each of the four isomers, when hydrolyzed independently of each other at pH 3.0 and 25°C, produced product mixtures in which the major product was damascenone (1). Contrary to expectation, 3-hydroxydamascone (5) was not observed in any of the hydrolyses. Consequently, the mechanism of formation of damascenone proposed earlier requires modification. In each hydrolysis, the product mixtures showed the presence of a second isomer of 8, produced by epimerization during hydrolysis. Chiral analysis on a Cyclosil B column revealed that this epimerization was occurring at C3 in each of the hydrolyses.
- Puglisi, Carolyn J.,Daniel, Merran A.,Capone, Dimitra L.,Elsey, Gordon M.,Prager, Rolf H.,Sefton, Mark A.
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- METHODS FOR SYNTHESIS OF CHIRAL INTERMEDIATES OF CAROTENOIDS, CAROTENOID ANALOGS, AND CAROTENOID DERIVATIVES
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A method used for synthesizing intermediates for use in the synthesis of carotenoids and carotenoid analogs, and/or carotenoid derivatives. In some embodiments, the invention includes methods for synthesizing optically active intermediates useful for the synthesis of optically active carotenoids.
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Page/Page column 40
(2010/10/20)
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- Lipase-catalyzed asymmetric synthesis of (R)- and (S)-4-tert-butyldimethylsilyloxy-2,6,6-trimethyl-2-cyclohexenone and their dihydro derivatives
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Racemic 4-hydroxy-2,6,6-trimethyl-2-cyclohexenone, trans- and cis-2,6,6-trimethyl-2-cyclohexene-1,4-diols were prepared by reduction of 4-oxoisophorone with sodium borohydride-cerium chloride. Lipase (PS-30)-catalyzed kinetic resolution of (±)-cis-2,6,6-trimethyl-2-cyclohexene-1,4-diol with vinyl acetate led to (1R, 4S)-4-acetoxy-2,6,6-trimethyl-2-cyclohexen-1-ol (81%ee) and (1S,4R)-1-acetoxy-2,6,6-trimethyl-2-cyclohexene-4-ol (92%ee). Hydrolysis of the former monoacetate and recrystallization of the resulting material afforded enantiomerically pure (1R, 4S)-2,6,6-trimethyl-2-cyclohexene-1,4-diol. On the other hand, recrystallization of (1S,4R) monoacetate itself provided an optically pure sample, which was then hydrolyzed to give (1S, 4R)-2,6,6-trimethylcyclohexene-1,4-diol. Transformation of both diols into (S)- and (R)-4-tert-butyldimethylsilyloxy-2,6,6-trimethyl-2-cyclohexenone was conducted in two steps including silylation and oxidation. Catalytic hydrogenation of these (S)- and (R)-silyloxy enones over Raney nickel afforded the corresponding dihydro derivatives.
- Tanaka,Yamamoto,Oritani
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p. 1273 - 1278
(2007/10/03)
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