Nouveaux alcaloïdes des feuilles de Strychnos usambarensis

Fourteen bis-indole alkaloids have been isolated from Strychnos usambarensis leaves. Nine are described here for the frst time: 18,19-dihydro-usambarine; usambaridines and their dihydroderivatives; strychnobaridine; strychnopentamine and isomers. The elucidation of structure and the stereochemistry of these new compounds are also discussed. They possess the "usambarane" skeleton; moreover many are phenolic and amongst them, strychnopentamine and isomers are curiuos alkaloids with five nitrogen atoms: a methylpyrrolidine group is joined to the indole ring of the corynane part of the molecule.