1. State Key Laboratory of Medicinal Chemical Biology College of Pharmacy Nankai University Haihe Education Park, 38 Tongyan Road Tianjin 300353 P. R. China
2. Key Laboratory of Functional Polymer Materials of Ministry of Education College of Chemistry Nankai University Tianjin 300071 P. R. China
3. State Key Laboratory of Medicinal Chemical Biology Nankai University Tianjin 300071 P. R. China