1. Department of Pharmacy, Ludwig-Maximilians University, Butenandtstrasse 5-13, München D-81377, Germany
2. Institute for Organic Chemistry and Macromolecular Chemistry, Friedrich-Schiller-University, Humboldtstrasse 10, Jena D-07743, Germany
3. Department of Chemistry, New York University, 100 Washington Square East, New York 10003, New York, United States