1. Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, 250012 Ji’nan, Shandong P. R. China
2. School of Pharmacy, University of Wisconsin—Madison, Madison, Wisconsin 53705, United States
3. Department of Chemistry, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States