1. Department of Pharmaceutical Biology and Biotechnology, Albert Ludwigs University Freiburg, Stefan-Meier-Strasse 19, D-79104 Freiburg, Germany
2. Spemann Graduate School of Biology and Medicine (SGBM), Albert Ludwigs University Freiburg, Albertstrasse 19a, 79104 Freiburg, Germany
3. Institute of Organic and Biomolecular Chemistry, Georg-August University, Tammannstrasse 2, 37077 Göttingen, Germany
4. Institute of Organic Chemistry II, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany