1. Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
2. Department of Biology, New York University, New York, NY 10003, USA
3. Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA
4. Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
5. Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA