Alcaloides Indoliques. VII. Structure de la Voacoline

Voacoline, a new minor alkaloid from Voacanga chalotiana Pierre ex Stapf (apocynaceae) is shown to have structure I. This structure contains two unusual features : a Na‐CH3 indolic group and a hemiketal function. This last feature accounts for the very easy formation of O‐methyl II and O‐ethyl‐voacoline HI. A correlation with voachalotine IV, the major alkaloid of the same species, has been achieved by degradation of I to dihydrodeshydroxymethylvoachalotine XIV. UV, IR, NMR and mass spectra of I and some of its derivatives are discussed.