1. Department of Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
2. Department of Health Science & Technology, ETH Zurich, Schmelzbergstrasse 9, 8092 Zürich, Switzerland
3. Institute of Organic Chemistry, Albert-Ludwigs-University of Freiburg, Albertstrasse 21, 79104 Freiburg i. B., Germany