As part of an extended chemotaxonomic study of the genus Tabernaemontana (Apocynaceae), we now describe the results of a study of the alkaloids of the African species, Tabernaemontana crassa Benth. The major alkaloid proved to be the known ibogamine-type base, conopharyngine (1). The second most abundant alkaloid was an amorphous base assigned the structure of 20-hydroxyconopharyngine (2), purified by a new procedure involving reaction with benzyl chloroformate to afford the crystalline carbobenzoxy ester 3, from which pure 2 was regenerated by hydrogenolysis. The structure of 2 was consistent with its spectral properties: ultraviolet absorption similar to conopharyngine (typical 5,6-dimethoxyindole), nuclear magnetic resonance showing methoxyls at δ 3.78 and 3.86 and aromatic protons at 6.71 and 6.83 (5,6-dimethoxyindole system), and mass spectrum analogous to heyneanine (4) with indole nucleus fragments 60 mass units heavier. It was confirmed by chemical conversion to ibogaline (5) via hydrolysis, decarboxylation to 20-hydroxyibogaline (6), tosylation to quaternary tosylate (7), and lithium aluminum hydride reduction. The least abundant base was a new crystalline alkaloid, crassanine (9), isomeric with 20-hydroxyconopharyngine (2). Its structure as the oxindole corresponding to conopharyngine was assigned based on infrared (two carbonyl groups), ultraviolet (similar to 5,6-dimethoxyoxindole alkaloids), nuclear magnetic resonance (methoxyls, aromatic protons, oxindole NH), and mass spectral data.