1. Department of Medicinal Chemistry College of Pharmacy, and Masonic Cancer Center University of Minnesota Minneapolis MN 55455 USA
2. Department of Biological Chemistry and Molecular Pharmacology Harvard Medical School Boston, MA 02115 USA
3. Current address: School of Science Westlake University Institute of Natural Sciences, Westlake Institute for Advanced Study 18 Shilongshan Road, 310024 Hangzhou Zhejiang Province China
4. Department of Chemistry University of Minnesota Minneapolis MN 55455 USA