1. Institute of Organic and Pharmaceutical Chemistry, National Hellenic Research Foundation, 48 Vass. Constantinou, Athens 116-35 Greece, Center for Drug Discovery, Northeastern University, 116 Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, and Faculty of Pharmacy, Department of Pharmaceutical Chemistry, University of Athens, Panepistimioupoli-Zografou, 15771, Athens, Greece