5-epi-canadensene and other novel metabolites of Taxus canadensis

The Canadian yew distinguishes itself from other yews by the nature of its taxane metabolites. We are now reporting a new canadensene taxane whose ste reochemistry is rigorously established. The three-dimensional structures of canadensene, 5-epi-canadensene and three other related bicyclic taxanes is olated from other yews were calculated using distance constraints derived f rom NMR data. The stereochemistry of the substituents, the polar acetate gr oups and the double bonds determine the 3D models. In addition, three new t axanes were also characterized and some biosynthetic speculations are prese nted. (C) 1998 Elsevier Science Ltd. All rights reserved.