1. Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260; Division of Pharmaceutics Sciences, College of Pharmacy, Department of Microbiology and Immunology, College of Medicine, and Experimental Therapeutics Program, Markey Cancer Center, University of Kentucky, Lexington, Kentucky 40506; Molecular Pharmacology Program, National Cancer Institute, Bethesda, Maryland 20892; and Tigen Pharmaceuticals, Inc., Lexington, Kentucky 40506