1. Department of Medicinal Chemistry and Molecular Pharmacology, School of Pharmacy and Pharmaceutical Sciences, and the Purdue Cancer Center, Purdue University, West Lafayette, Indiana 47907, Imquest Biosciences, 7340 Executive Way, Suite R, Frederick, Maryland 21704, and Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium