From oil of carrot seeds, Daucus carota L., Umbelliferae: Richter, Arch. Pharm. 247, 391 (1909). Structure: Sykora et al., Collect. Czech. Chem. Commun. 26, 788 (1961); Zalkow et al., J. Org. Chem. 26, 981 (1961). Stereochemistry: Levisalles, Rudler, Bull. Soc. Chim. Fr. 1964, 2020; 1967, 2059. Synthesis of (-)-form: DeBroissia et al., Chem. Commun. 1972, 855; eidem, Bull. Soc. Chim. Fr. 1972, 4314.