In root bark of Punica granatum L., Punicaceae. Extraction procedure: Hess, Eichel, Ber. 50, 380, 1391, 1395 (1917); ibid. 52, 1012 (1919). Synthesis under physiological conditions from calcium acetonedicarboxylate, glutardialdehyde, and methylamine: Menzies, Robinson, J. Chem. Soc. 1924, 2163; cf. Sch"opf, Angew. Chem. 50, 779, 797 (1937). Alternate syntheses: Cope et al., Org. Synth. 37, 73 (1957); Robinson, Hunt, J. Pharm. Pharmacol. 22, 29S (1970); Bottini, Gal, J. Org. Chem. 36, 1718 (1971). Conformation: Chen, LeFevre, J. Chem. Soc. B 1966, 539.