The invention relates to novel bioactive polycyclic ether compounds comprising a spiro-linked five-membered cyclic imine. In particular, the invention relates to a compound designated portimine, its congeners and the use of these compounds in anticancer therapy. In a second aspect the invention provides a pharmaceutical preparation comprising as active ingredient a congener of the first aspect of the invention. Preferably, the pharmaceutical preparation is indicated for use in the treatment of subjects with neoplasia. More preferably, the pharmaceutical preparation is indicated for use in the treatment of subjects with lymphoid malignancies. Preferably, the lymphoid malignancies are selected from the group consisting of: chronic lymphocytic leukaemia (CLL) and pediatric acute lymphoblastic leukaemia (ALL).