1. Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China
2. State Key Laboratory of Synthetic Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong 999077, P. R. China
3. State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
4. Department of Medicinal Chemistry, Shantou University Medical College, Shantou, Guangdong 515041, P. R. China