Carotenoid pigment found widely distributed in nature, but in very small amounts only. One of very few carotenoids with retro configuration. Best isolated from the arils of Taxus baccata L., Taxaceae: Kuhn, Brockmann, Ber. 66, 828 (1933). Occurs also in the feathers of birds such as Phoenicircus nigricollis, Megaloprepia magnifica. Isoln: Volker, Z. Physiol. Chem. 292, 75 (1953). Structure: Kuhn, Brockmann, loc. cit.; Karrer, Solmssen, Helv. Chim. Acta 18, 477 (1935). Synthesis: Mayer et al., ibid. 50, 1606 (1967); Surmatis, Walser, US 3466331; US 3624105 (1969, 1971 to Hoffmann-La Roche); P. R. Ellis et al., Helv. Chim. Acta 64, 1092 (1981); E. Widmer et al., ibid. 65, 944 (1982). Review: Liaaen-Jensen in Aspects Terpenoid Chem. Biochem., Proc. Phytochem. Soc. Symp., 2nd, 1970, T. W. Goodwin, Ed. (Academic Press, London, 1971) p 223-254.