5′-O-demethyldioncophylline A, a new antimalarial alkaloid from triphyophyllum peltatum1Part 111 in the series “Acetogenic Isoquinoline Alkaloids”. For Part 110, see Ref.[1].1

From the root bark of Triphyophyllum peltatum, the new naphthylisoquinoline alkaloid 5'-O-demethyldioncophylline A has been isolated. Its otherwise difficult separation from the largely dominating main alkaloid, dioncophylline A, was greatly facilitated by a bromination-benzylation procedure. From the resulting derivative, a crystal structure analysis with an anomalous X-ray diffraction was achieved, allowing confirmation of the full absolute stereostructure of the new alkaloid. The structure was further corroborated by a partial synthesis from dioncopeltine A. The natural product was shown to exhibit antimalarial activity against erythrocytic forms of Plasmodium falciparum. (C) 1998 Elsevier Science Ltd. All rights reserved.