Efficient syntheses of the keto-carotenoids canthaxanthin, astaxanthin, and astacene.
Three keto-carotenoids were prepared by the oxidation of the stable C(40) trisulfone 6, which has been used as the key compound in our beta-carotene synthesis. The first allylic oxidation to the unsaturated ketone and the second oxidation to the alpha-hydroxyketone produced the C(40) trisulfones 7 and 10, respectively. The Ramberg-Backlund reaction of the oxidized C(40) trisulfone was efficiently effected by the use of a mild base, NaOMe, in the presence of CCl(4) as a halogenating agent to give the C(40) disulfones 8 and 11. Base-promoted dehydrosulfonation reaction of the disulfone compounds produced the fully conjugated polyenes of canthaxanthin (1), astaxanthin (2), and astacene (3).
Choi
Seyoung
S
Department of Chemistry, Myong Ji University, Yongin, Kyunggi-Do 449-728, Korea.
Koo
Sangho
S
D016644:Canthaxanthin / Q000138:chemical synthesis*; D002338:Carotenoids / Q000138:chemical synthesis*; D020650:Combinatorial Chemistry Techniques; D015394:Molecular Structure; D010084:Oxidation-Reduction; D024341:Xanthophylls; D019207:beta Carotene / Q000031:analogs & derivatives* / Q000138:chemical synthesis*
D024341:Xanthophylls; C500293:astacene; D019207:beta Carotene; D002338:Carotenoids; D016644:Canthaxanthin; C005948:astaxanthine