Obtained from glucosides found in various species of Convolvulaceae, e.g., convolvulin, jalapin, β-turpethein. Isoln: Votocek, Z. Zuckerind. Boehm. 24, 249; Chem. Zentralbl. 1901, I, 1042; 1902, II, 1361; 1905, II, 1528. Isoln from jalap resin: Votocek, Bulir, ibid. 1906, I, 1818. Prepn by acid hydrolysis of chartreusin: Sternbach et al., J. Am. Chem. Soc. 80, 1639 (1958).