1. School of Pharmacy, Jinan University, 601 Huangpu Avenue West, Guangzhou 510632, China
2. Department of Chemistry, City University of Hong Kong, Hong Kong 999077, China
3. School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
4. Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore