1. 8.2 Pharmaceutical and Medicinal Chemistry, Saarland University, P.O. Box 15 11 50, D-66041 Saarbrücken, Germany, Pharmacelsus CRO, Science Park 2, D-66123 Saarbrücken, Germany, and Solvay Pharmaceuticals Research Laboratories, Hans-Böckler-Allee 20, D-30173 Hannover, Germany