1. Pharmaceutical R & D Division, Recordati s.p.a., Via Civitali 1, 20148 Milano, Italy, Pharmaco-Chemistry and Toxicology Institute, University of Milano, V.le Abruzzi 42, 20131 Milano, Italy, Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, Italy, and Dulbecco Telethon Institute (DTI) and Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, Italy