New monomeric naphthylisoquinoline alkaloids, yaoundamines A and B, were isolated from Ancistrocladus korupensis and their structures were determined by extensive chemical and spectroscopic analyses. The absolute configuration at C3 was established by chemical degradation, while the axial chirality was deduced by comparison of experimental and calculated CD spectra. Yaoundamine B has an unprecedented glycosylated naphthylisoquinoline structure. Yaoundamines A and B are active in vitro against the malaria parasite Plasmodium falciparum. .