Two isomers, (5) and (6), 1-phenyl-1,2,3,4-tetraline-1,4-dicarboxylic acid discopine ester, were isolated from the leaves of Duboisia leichhardtii F. Muell (Solanaceae), and their structures and stereochemistry were studied on the basis of spectral data and synthesis. Also, four known alkaloids, isobutyroyl tropine (1), norhyoscyamine (2), aposcopolamine (3), and apoatropine (4), were identified. 13C-nuclear magnetic resonance spectral data regarding these alkaloids and corresponding compounds were discussed.