1. Laboratory of Pharmaceutical Chemistry and Radiopharmacy, Department of Pharmaceutical Sciences, School of Pharmacy, Faculty of Medicine, Catholic University of Louvain, 73, Avenue E. Mounier, UCL-CMFA 73.40, B-1200 Brussels, Belgium, and Department of Pharmaceutical Chemistry, University of Münster, Hittorfstrasse 58-62, 48149 Münster, Germany