1. Faculty of Chemistry and MineralogyInstitute of Organic ChemistryUniversity of Leipzig Johannisallee 29 04301 Leipzig Germany
2. Swiss Tropical and Public Health Institute Socinstrasse 57 4051 Basel Switzerland
3. University of Basel, Petersplatz 1 4003 Basel Switzerland
4. Department of Pharmaceutical BiologyInstitute of Pharmacy and BiochemistryUniversity of Mainz Staudinger Weg 5 55128 Mainz Germany