1. Departments of Chemistry and Pharmacology & Toxicology, Queen's University, Kingston, Ontario, K7L 3N6, Canada, Department of Chemistry, Mount Allison University, Sackville, New Brunswick, E4L 1G8, Canada, and Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago, 833 Wood Street, Chicago, Illinois 60612-7231