Isoln from calabash-curare: Wieland, Pistor, Ann. 536, 68 (1938); Karrer, Schmid, Helv. Chim. Acta 29, 1853 (1946); Zürcher et al., J. Am. Chem. Soc. 80, 1500 (1958). Structure: Nagyvàry et al., Tetrahedron 14, 138 (1961); Grdinic et al., J. Am. Chem. Soc. 86, 3357 (1964); Jones, Nowacki, Chem. Commun. 1972, 805. Prepn of C-dihydrotoxiferine chloride: Bernauer et al., Helv. Chim. Acta 40, 1999 (1957).