1. Institut für Pharmazeutische Chemie, Westfälische Wilhelms-Universität Münster, Hittorfstrasse 58-62, 48149 Münster, Germany, Department of Microbiology, University of Innsbruck, Medical School, Fritz-Pregl-Strasse 3, 6020 Innsbruck, Austria, and German Cancer Research Center, Division C0200, Toxicology and Cancer Risk Factors, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany