1. Department of Chemistry and Applied Biosciences Institute of Pharmaceutical Sciences ETH Zurich HCI H405 Vladimir-Prelog-Weg 4 8093 Zürich Switzerland
2. Centro de Investigaciones Biolόgicas Margarita Salas Consejo Superior de Investigaciones Científicas Ramiro de Maeztu 9 28040 Madrid Spain
3. Department of Chemistry and Applied Biosciences Institute of Biochemistry and Molecular Medicine University of Bern Bühlstrasse 28 3012 Bern Switzerland