1. State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu Chong Zhi Road, Shanghai 201203, P. R. China
2. Department of Chemistry, Shanghai University, 99 Shang Da Road, Shanghai 200444, P. R. China
3. School of Pharmacy, University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, P. R. China