44
/. Isoprenoids
ο
104
presence of air. Kuhn and Sorensen (1938) explained this transformation as
an alkaline oxidation of an a-ketol to an α-diketone that, according to more
recent data (Davis and Weedon, 1960), is enolized in solution. Both astaxanthin (103) and astacene (104) have been synthesized by Weedon and collaborators (Davis and Weedon, 1960; Leftwick and Weedon, 1967). Astaxanthin
(103) has also been recognized as a pigment in the gonads of the sea cucumbers
Holothuria leucospilota (Matsuno et ah, 1969) and Stichopus
japonicus
(Matsuno and Ito, 1971).
A closely related carotenoid, a-doradecin (105), was recently isolated from
the goldfish Crassius auratus, where it occurs as the ester (a-doradexanthin
ester). Its structure was secured by spectral comparison and by sodium
borohydride reduction to, and ultraviolet spectral comparison with, lutein
Ο
105
106
(106) by Katayama and co-workers (1970a,b). The authors suggest that
a-doradecin may be a metabolic intermediate in the oxidation pathway of the
plant carotenoids ß-earotene (95) and lutein (106) to the highly oxidized
animal carotenoid astacene (104).
Two structurally related xanthophylls, the common feature of which is an
oxygenated C-9 methyl group, have been isolated from several species of
/. Isoprenoids
ο
104
presence of air. Kuhn and Sorensen (1938) explained this transformation as
an alkaline oxidation of an a-ketol to an α-diketone that, according to more
recent data (Davis and Weedon, 1960), is enolized in solution. Both astaxanthin (103) and astacene (104) have been synthesized by Weedon and collaborators (Davis and Weedon, 1960; Leftwick and Weedon, 1967). Astaxanthin
(103) has also been recognized as a pigment in the gonads of the sea cucumbers
Holothuria leucospilota (Matsuno et ah, 1969) and Stichopus
japonicus
(Matsuno and Ito, 1971).
A closely related carotenoid, a-doradecin (105), was recently isolated from
the goldfish Crassius auratus, where it occurs as the ester (a-doradexanthin
ester). Its structure was secured by spectral comparison and by sodium
borohydride reduction to, and ultraviolet spectral comparison with, lutein
Ο
105
106
(106) by Katayama and co-workers (1970a,b). The authors suggest that
a-doradecin may be a metabolic intermediate in the oxidation pathway of the
plant carotenoids ß-earotene (95) and lutein (106) to the highly oxidized
animal carotenoid astacene (104).
Two structurally related xanthophylls, the common feature of which is an
oxygenated C-9 methyl group, have been isolated from several species of