INSERM U-524 et Laboratoire de Pharmacologie Antitumorale du Centre Oscar Lambret, IRCL, Place de Verdun, 59045 Lille, France, Biospectroscopy and Physical Chemistry Unit, Department of Chemistry and Natural and Synthetic Drugs Research Center, University of Liege, Sart-Tilman, 4000 Liege, Belgium, and Departamento de CC. Químicas, Facultad de CC Experimentales y de la Salud, Universidad San Pablo-CEU, Urb. Montepríncipe, Boadilla del Monte, 28668 Madrid, Spain (At 2003-03-21)