Antiprotozoal Spirombandakamines A1 and A2, Fused Naphthylisoquinoline Dimers from a Congolese Ancistrocladus Plant

From the leaves of a yet undescribed Congolese Ancistrocladus species, two novel naphthylisoquinoline dimers, spirombandakamines A 1 ( 1 ) and A 2 ( 2 ), were isolated, together with a new, but “classical” dimer, mbandakamine B 2 ( 3 ). The cage-like stereostructures of 1 and 2 were established by combining spectroscopic, chemical, and chiroptical methods with quantum-chemical ECD calculations. Their unique molecular frameworks may originate from “open-chain” dimers, such as 3, by an oxidation-induced cascade of reactions. They possess strong antiprotozoal properties.