1. Institut für Pharmazeutische und Medizinische Chemie Heinrich-Heine-Universität Düsseldorf Universitätsstr. 1 40225 Düsseldorf Germany
2. Department of Pediatric Oncology, Hematology and Clinical Immunology, Medical Faculty Heinrich Heine University Düsseldorf Universitätsstr. 1 40225 Düsseldorf Germany
3. Department of Medicine Yangzhou Polytechnic College West Wenchang Road 458 Yangzhou 225009 P.R. China
4. Institute for Drug Discovery, Medical Faculty Leipzig University Brüderstraße 34 04103 Leipzig Germany
5. Pharmaceutical and Cell Biological Chemistry, Pharmaceutical Institute University of Bonn An der Immenburg 4 53121 Bonn Germany