Found in the tubers of Dioscorea hirsuta Blume and D. hispida Dennst., Dioscoreaceae: H. W. Schutte, Chem. Zentralbl. 68, II, 130 (1897); M. K. Gorter, Rec. Trav. Chim. 30, 161 (1911); A. R. Pinder, Nature 168, 1090 (1951); idem, J. Chem. Soc. 1952, 2236. Structure: W. A. M. Davies et al., Chem. Ind. (London) 1961, 1410; eidem, Tetrahedron 18, 405 (1962); Morris, A. R. Pinder, J. Chem. Soc. 1963, 1841. Synthesis: Page, A. R. Pinder, ibid. 1964, 4811. Absolute configuration: A. F. Beecham et al., Tetrahedron Lett. 1969, 3745. Biosynthetic studies: E. Leete, A. R. Pinder, Chem. Commun. 1971, 1499; E. Leete, J. Am. Chem. Soc. 99, 648 (1977). Pharmacology: A. R. Pinder, J. Chem. Soc. 1953, 1826. Evaluation of toxic components: J. Webster et al., J. Agric. Food Chem. 32, 1087 (1984).