1. Department of ChemistryUniversity of Konstanz Universitätsstrasse 10 78457 Konstanz Germany
2. Konstanz Research School Chemical Biology (KoRS-CB)University of Konstanz Universitätsstrasse 10 78457 Konstanz Germany
3. Present address: Faculty of ScienceDepartment of Pharmaceutical BiologyUniversity of Tübingen Auf der Morgenstelle 8 72076 Tübingen Germany
4. Faculty of Chemistry and Chemical BiologyTU Dortmund Otto-Hahn-Strasse 4a 44227 Dortmund Germany