Eight (Z)-isomers of lycopene were prepared by stereocontrolled syntheses and fully characterized by '€1-NMR, "C-NMR, mass, and UVjVIS spectroscopy: (5Z)-, (72)
Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. VIII. Synthesis of (3S,3′S)‐7,8,7′,8′‐Tetradehydroastaxanthin and (3S,3′S)‐7,8‐Didehydroastaxanthin (Asterinic Acid)
The synthesis of all‐trans‐(3S,3′S)‐3,3′‐dihydroxy‐7,8, 7′,8′‐tetradehydro‐β, β‐carotene‐4,4′‐dione (1), of all‐trans‐(3S,3′S)‐3,3′‐dihydroxy‐7, 8‐didehydro‐β,β‐carotene‐4,4′‐dione (2) (asterinic acid = mixture of 1 and 2), and of their 9,9′‐di‐cis‐ and 9‐cis‐isomers is reported starting from (4′S)(2E)‐5‐(4′‐hydroxy‐2′, 6′,6′‐trimethyl‐3′‐oxo‐l′‐cyclohexenyl)‐3‐methyl‐2‐penten‐4‐ynal (8). The absolute configuration (3S,3′S) for both components 1 and 2 of asterinic acid ex Asterias rubens is confirmed on the basis of spectroscopic and direct comparison.
Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. IX. Synthesis of (3R)‐Hydroxyechinenone, (3R, 3′R)‐ and (3R, 3′S)‐Adonixanthin, (3R)‐Adonirubin, Their Optical Antipodes and Related Compounds
The synthesis of racemic and optically active hydroxyechinenone (12–14), adonixanthin (16–19), adonirubin (22–24), meso‐astaxanthin (26) and their corresponding diosphenols 15, 20, 21, 25, 27, 28, and 29) by Wittig reaction is reported, starting from suitable C15‐phosphonium salts and C10‐aldehydes.
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