The isolation of a new alkaloid, dioncophylline B, from the roots of Triphyophyllum peltatum is described. Its complete structure, including absolute configuration, was established by spectroscopic and degradative methods. Dioncophylline B has an unprecedented 7,6′-coupling, and is, because of the lack of bulky substituents next to its axis, the first 'non-bridged' naphthylisoquinoline alkaloid that is not split up into stable atropisomers. © 1991.