1. Department of Chemistry, Developmental Therapeutics Program, Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan 48201-1379, Department of Internal Medicine II, Kumamoto University School of Medicine, Honjo 1-1-1 Kumamoto 860, Japan, and Experimental Retrovirology Section, HIV and AIDS Malignancy Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892