1. Cancer Research Laboratories, Department of Pharmaceutical Sciences, University of Nottingham, Nottingham NG7 2RD, U.K., Pharmaceutical Sciences Institute, Aston University, Aston Triangle, Birmingham B4 7ET, U.K., Aston Molecules Ltd, 10 Holt Court South, Aston Science Park, Birmingham B7 4EJ, U.K., and Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202