1. Dipartimento di Scienze Chimiche, Alimentari, Farmaceutiche e Farmacologiche, Università del Piemonte Orientale, Viale Ferrucci 33, 28100 Novara, Italy, Department of Organic and Bioorganic Chemistry, Lund University, P.O. Box 124, 221 00 Lund, Sweden, Indena S.p.A. Viale Ortles 12, 20139 Milano, Italy, and Department of Experimental Therapeutics, Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, New York 14263