1. Institute of Pharmaceutical Biology and Biotechnology, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany
2. Department of Organic Chemistry, University of Debrecen, PO Box 400, 4002 Debrecen, Hungary
3. Institute of Complex Systems: Strukturbiochemie (ICS-6), Forschungszentrum Jülich, Wilhelm-Johnen-Strasse, 52428 Jülich, Germany
4. Faculty of Science, Department of Chemistry, University of Douala, PO Box 24157, Douala, Cameroon
5. Institute of Pharmaceutical and Medicinal Chemistry, Heinrich Heine University, Universitätsstrasse 1, 40225 Düsseldorf, Germany