1. School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300401, P. R. China
2. Hebei Key Laboratory of Heterocyclic Compounds, Handan 056005, P. R. China
3. College of Chemical Engineering and Materials, Handan University, Handan 056005, P. R. China
4. School of Pharmacy, Guangdong Pharmaceutical University, Guangzhou 510006, P. R. China