1. Department of Chemistry, M/C 0212, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0212, United States
2. Missouri Botanical Garden, B.P 3391, Antananarivo 101, Madagascar
3. Centre National d’Application des Recherches Pharmaceutiques, B.P 702, Antananarivo 101, Madagascar
4. Next Generation Systems, Eisai Inc., 4 Corporate Drive, Andover, Massachusetts 01810, United States