In the alkaline mother liquors from morphine extraction, in amounts corresp to about 0.005% of the opium employed: L. F. Small, R. E. Lutz, Chemistry of the Opium Alkaloids, Supplement No. 103, Public Health Reports, Washington (1932) p 34. Structure: Spth, Monatsh. Chem. 41, 297 (1920). Synthesis: Spth, Lang, ibid. 42, 273 (1921); Frydman et al., Tetrahedron 4, 342 (1958).