Isoln from toads: Wieland et al., Ann. 513, 1 (1934); Wieland, Wieland, ibid. 528, 239 (1937); from toadstools: Wieland, Motzel, ibid. 581, 10 (1953). Isoln from Piptadenia peregrina Benth., Leguminosae: Stromberg, J. Am. Chem. Soc. 76, 1707 (1954). Synthesis: Hoshino, Shimodaira, Ann. 520, 19 (1935); Harley-Mason, Jackson, Chem. Ind. (London) 1952, 954; see also Serotonin; and Speetor, US 2708197 (1955 to Upjohn); Stoll et al., Helv. Chim. Acta 38, 1452 (1955). Activity: Bhattacharya, Sanyal, Indian J. Physiol. Pharmacol. 15, 133 (1971). Crystal and molecular structure: G. Falkenberg, Acta Crystallogr. 28B, 3219 (1972).