1. Department of Medicinal Chemistry, School of Pharmacy, Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia 23298-0133, Allos Therapeutics, Inc., 11080 CirclePoint Road, Suite 200, Westminster, Colorado 80020, and Physiologie et Physiopathologie Moleculaires, INSERM U 473, 84 Rue du General Leclerc, 94276 Le Kremlin Bicetre Cedex, France