1. School of Chemistry and Chemical Engineering, Anhui University of Technology, Ma'anshan, Anhui 243002, P. R. China
2. School of Pharmaceutical Sciences & Institute of Materia Medica, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan 250117, Shandong, China
3. State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. China