Subacute Combined Degeneration of the Spinal Cord
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- ↑ Choi S & Koo S: Efficient syntheses of the keto-carotenoids canthaxanthin, astaxanthin, and astacene. J Org Chem 2005. (PMID 15823009) [PubMed] [DOI] 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).