1. Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States
2. Institute of Medical Microbiology, University of Zurich, 28 Gloriastrasse, 8006 Zürich, Switzerland
3. Organic Chemistry Laboratory, ETH Zürich, Vladimir-Prelog-Weg 1-5/10, 8093 Zürich, Switzerland