1. Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania 15282, Department of Pharmacology and Toxicology, School of Medicine, Indiana University, Indianapolis, Indiana 46202, Department of Biochemistry, School of Medicine, Tufts University, Boston, Massachusetts 02111, and Hauptman-Woodward Medical Research Institute Inc., 73 High Street, Buffalo, New York 14203