1. Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, Department of Chemistry, University of Tartu, Jakobi Street 2, Tartu 51014, Estonia, and 3-Dimensional Pharmaceuticals, Inc., 665 Stockton Drive, Suite 104, Exton, Pennsylvania 19341