1. National Glycoengineering Research Center, Shandong Provincial Key Laboratory of Carbohydrate Chemistry and Glycobiology, NMPA Key Laboratory for Quality Research and Evaluation of Carbohydrate Based Medicine, Shandong University, Qingdao 266237, Shandong, China
2. Key Laboratory of Chemical Biology of Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, Shandong, China
3. Department of Chemistry, University of Konstanz, D-78457 Konstanz, Germany