1. Key Laboratory of Medicinal Chemistry for Natural Resources, Ministry of Education, Yunnan Province Center for Research & Development of Natural Products, School of Chemical Science and Technology, Yunnan University, Kunming, 650091, P. R. China
2. Roy and Diana Vagelos Laboratories Penn/Merck Laboratory for High-Throughput Experimentation Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA, USA