1. Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Otto Hahn Strasse 11, 44227 Dortmund, Germany, Department of Chemistry, TU Dortmund, Otto Hahn Strasse 6, 44227 Dortmund, Germany, and Chemical Genomics Centre of the Max Planck Society, Otto Hahn Strasse 15, 44227, Dortmund, Germany