1. Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy (MC 781), University of Illinois at Chicago, 833 S. Wood Street 539, Chicago, Illinois 60612, Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas 77555-1031, and Georgetown University Medical Center, 3900 Reservoir Road, N.W., Washington, DC 20007