Contribution from the Department of Chemistry, Georgia State University, P.O. Box 4098, Atlanta, Georgia 30302-4098, INSERM U-524 et Laboratoire de Pharmacologie Antitumorale du Centre Oscar Lambret, IRCL, Place de Verdun, 59045 Lille, France, and Cancer Research UK Biomolecular Structure Group, The School of Pharmacy, University of London, London WC1N 1AX, United Kingdom (At 2004-09-29)