1. Department of Applied Chemistry, Faculty of Science, Kunming University of Science and Technology, Kunming, Yunnan, 650500, China
2. Key Laboratory of Medicinal Chemistry for Natural Resource, (Ministry of Education), School of Chemical Science and Technology, Yunnan University, Kunming Yunnan, 650091, China
3. Chemical Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702, United States