1. Department of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou, 450001, China
2. Department of Medicinal Chemistry, School of Pharmacy, Fudan University, Shanghai, 201203, China
3. Complex Carbohydrate Research Center, the University of Georgia, Athens, 30605, GA, USA
4. State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, China