1. Max-Planck-Institute for Dynamics and Self-Organization, Am Fassberg 17, 37077 Göttingen, Germany
2. Institute of Organic and Biomolecular Chemistry, Georg-August-Universität, Tammannstraße 2, 37077 Göttingen, Germany
3. Institute of Organic Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany