1. Laboratory of Medicinal Chemistry, Building 8, Room B1-23, National Institute of Diabetes and Digestive and Kidney Diseases, and Biological Psychiatry Branch, National Institute of Mental Health, National Institutes of Health, 9000 Rockville Pike, Bethesda, Maryland 20892, and Clinical Psychopharmacology Section, IRP, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224