1. School of Pharmaceutical Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa 920-1192, Japan
2. School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
3. The Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7568, United States
4. NIH Special Volunteer, Wayne, Pennsylvania 19087, United States
5. Natural Products Branch, Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, NCI at Frederick, Frederick, Maryland 21702-1201, United States
6. Molecular Targets Program, Center for Cancer Research, National Cancer Institute, NCI at Frederick, Frederick, Maryland 21702-1201, United States