1. Department of Chemistry and Chemical Engineering, Institute of Chemometrics and Pharmacy (ICP), Hunan University, Changsha 410082, P.R. China, Department of Chemistry, Xiangtan Teacher's College, Xiangtan 411100, P.R. China, and College of Chemistry and Chemical Engineering, Institute of Molecular Pharmacy (IMP), Chongqing University, Chongqing 630044, P.R. China