1. Department of Chemistry, University of Southern California, Los Angeles, California 90089-1062, United States
2. Department of Medicinal Chemistry, Center for Natural Products, Drug Discovery and Development (CNPD3), Genetics Institute, University of Florida, Gainesville, Florida 32610, United States
3. State Key Laboratory of Natural and Biomimetic Drugs, Chemical Biology Center, and School of Pharmaceutical Sciences, Peking University, Beijing 100191, China