Ancistroheynine A, the first 7,8'-coupled naphtylisoquinoline alkaloid from Ancistrocladus heyneanus

The isolation and structural elucidation of a novel naphthylisoquinoline alkaloid, named ancistroheynine A, from the Indian liana Ancistrocladus heyneanus is described. The absolute configuration at the stereocentre was established by oxidative degradation to give S-3-aminobutyric acid. The axial configuration was unambiguously determined by long-range nuclear Overhauser enhancement (NOE) measurements, which covered the, as yet, longest distance within this class of compounds. Ancistroheynine A is the first 7,8′-coupled naphthylisoquinoline alkaloid found in A. heyneanus. Its accumulation in spherical inclusions is strongly enhanced in aging parts of the plant. It displays pronounced in vitro activity against Plasmodium falciparum, the most lethal human malaria parasite.