The isolation and structural elucidation of two novel naphthylisoquinoline alkaloids, dioncophylline D and its 8-O-methyl analogue, from the West African liana Triphyophyllum peltatum are described. Their structures are based on the rare 7,8'-coupling between the two molecular moieties. The absolute configuration at the stereocentres of the isoquinoline half was established by oxidative degradation to give R-3-aminobutyric acid and D-alanine. Both alkaloids are characterized by a rapid rotation around the biaryl axis. The two new alkaloids are apparently found in young (carnivorous) plants, exclusively. (C) 1998 Elsevier Science Ltd. All rights reserved.