1. Dipartimento Farmaco Chimico Tecnologico, University of Cagliari, Via Ospedale 72, 09124 Cagliari, Italy, Dipartimento di Scienze Chimiche, University of Cagliari, Complesso di Monserrato, 09042 Monserrato, Italy, and Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, Wolfgang-Pauli-Strasse 10, CH-8057 Zurich, Switzerland