A novel, selective, and efficient route to carotenoids and related natural products via Zr-catalyzed carboalumination and Pd- and Zn-catalyzed cross coupling.
[structure: see text]. A highly efficient and stereoselective protocol for the syntheses of symmetrical and unsymmetrical carotenoids involving Zr-catalyzed carboalumination of conjugated oligoenynes and Pd- and Zn-catalyzed alkenyl-alkenyl coupling has been developed and applied to the syntheses of beta- and gamma-carotene and vitamin A. gamma-Carotene of > or =99% isomeric purity was prepared in three linear steps (five steps overall) from beta-ionone, enyne 8, (E)-ICH=CHBr, and (E)-Me3SiC triple bond CCH=CHBr in 32% overall yield.
Zeng,Negishi
p. 719 - 722
(2007/10/03)
Retinoids. 6. Preparation of alkyl- and trimethylsilyl-substituted retinoids via conjugate addition of cuprates to acetylenic esters
Five retinoids bearing the ethyl, tert-butyl, and trimethylsilyl groups in the 9-position of retinal and the ethyl and tert-butyl groups in the 13-position have been synthesized. The key step of the syntheses involves the conjugate addition of lithium die
Ernst, Ludger,Hopf, Henning,Krause, Norbert
p. 398 - 405
(2007/10/02)
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