1. Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, Florida 32611-7200, 3-Dimensional Pharmaceuticals, Inc., 665 Stockton Drive, Suite 104, Exton, Pennsylvania 19341, and Department of Chemistry, University of Tartu, 2 Jakobi Street, Tartu EE 2400, Estonia