1. Institute for Organic Chemistry Gottfried Wilhelm Leibniz University Hannover Schneiderberg 1b 30167 Hannover Germany
2. Bachem AG Hauptstrasse 144 4416 Bubendorf Switzerland
3. Centre of Biomolecular Drug Research (BMWZ) Gottfried Wilhelm Leibniz University Hannover Schneiderberg 38 30167 Hannover Germany