Ancistrobertsonines B, C, and D as well as 1,2-didehydroancistrobertsonine D from Ancistrocladus robertsoniorum

From the East African Liana Ancistrocladus robertsoniorum, four new naphthylisoquinoline alkaloids have been isolated using High Speed Countercurrent Chromatography (HSCCC) and High Performance Liquid Chromatography (HPLC). Their stereostructures were established by spectroscopic, chemical, and chiroptical methods. Two of the new compounds, ancistrobertsonines B and C, constitute O- and N-permethylated 5,1'-coupled and 5,8'-coupled regioisomeric naphthylisoquinolines, while ancistrobertsonine D and its 1,2-didehydro analogue are based on a 7,1'-coupling mode between the isoquinoline and naphthalene moieties. Biological tests revealed that some of the isolated alkaloids possess moderate antimalarial activities. (C) 1999 Elsevier Science Ltd. All rights reserved.