1. Karmanos Cancer Research Institute, School of Medicine, 9374 Scott Hall, Wayne State University, Detroit, Michigan 48201, Department of Chemistry, University of MissouriRolla, Rolla, Missouri 65409, Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Centre, Houston, Texas 77030, and Department of Chemistry, University of MissouriSt. Louis, St. Louis, Missouri 63121