1. Department of Pharmaceutical Sciences, University of Southern California, School of Pharmacy, 1985 Zonal Avenue, Los Angeles, California 90089, Laboratory of Medicinal Chemistry, Center for Cancer Research, NCIFrederick, Frederick, Maryland 21702, Laboratory of Molecular Pharmacology, Division of Basic Sciences, National Cancer Institute, Bethesda, Maryland 20892, Southern Research Institute, 431 Aviation Way, Frederick, Maryland 21701, and Fox Chase Cancer Center, Philadelphia, Pennsylvania