1. Division of Medicinal Chemistry and Natural Products, School of Pharmacy, CB# 7360, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7360, Department of Chemistry, University of Houston, Houston, Texas 77204-5641, and Epilepsy Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, 6001 Executive Boulevard, Suite 2106, Rockville, Maryland 20852