1. Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources (Ministry of Education), School of Chemistry & Chemical Engineering, Guangxi Normal University, Guilin 541004, P. R. China
2. College of Chemistry and Life Science, Tianjin Key Laboratory of Structure and Performance for Functional Molecule, Tianjin Normal University, Tianjin 300387, P. R. China
3. Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China