1. Laboratory of Natural Products, Jiangsu Simcere Pharmaceutical R&D Company, Ltd., 699-18 Xuanwu Road, Xuanwu District, Nanjing 210042, People’s Republic of China, Department of Natural Medicine Chemistry, China Pharmaceutical University, Nanjing 210009, People’s Republic of China, and Institute of Functional Biomolecules, State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, People’s Republic of China