1. Department of Chemistry University of Florida PO Box 117200 Gainesville FL 32608 USA
2. Department of Medicinal Chemistry and Center for Natural Products, Drug Discovery and Development (CNPD3) University of Florida Gainesville FL 32610 USA
3. Department of Medicinal Chemistry University of Minnesota Minneapolis MN 55455 USA
4. Department of Chemistry University of Minnesota Minneapolis MN 55455 USA