Studies on Oxidopyrylium [5 + 2]
Cycloadditions: Toward a General
Synthetic Route to the C12-Hydroxy
Daphnetoxins
Paul A. Wender,*F. Christopher Bi,Nicole Buschmann,Francis Gosselin,Cindy Kan,Jung-Min Kee, andHirofumi Ohmura
Department of Chemistry, Stanford University, Stanford, California 94305-5080, and
Department of Molecular Pharmacology, Stanford University School of Medicine,
Stanford University, Stanford, California 94305
wenderp@stanford.edu
Received September 8, 2006
Abstract:
12-Hydroxydaphnetoxins, members of the structurally fascinating daphnane diterpene family, exhibit a wide range of significant biological
activities. A general route to the BC-ring system of 12-hydroxy daphnetoxins is reported based on D-ribose. Depending on the choice of
protecting groups and solvent, the oxidopyrylium-alkene [5 + 2] cycloaddition originating from A provides cycloadduct diastereomer B or C
with good to excellent selectivity.
