1. School
of Pharmacy, Yancheng Teachers University, Yancheng 224051, P. R. China
2. Key
Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry,
Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, P. R. China
3. Hainan Chuntch Pharmaceutical Company Limited, Haikou 570216, P. R. China