1. Department of Chemistry, Aalen University, Beethovenstrasse 1, 73430 Aalen, Germany
2. Department of Pharmaceutical and Medicinal Chemistry, Friedrich Schiller University Jena, 07743 Jena, Germany
3. Departments of Chemistry and Molecular Biosciences, the Chemistry of Life Processes Institute, and the Proteomics Center of Excellence, Northwestern University, Evanston, Illinois 60208, United States
4. F. Hoffmann La-Roche Ltd., Grenzacherstraße 124, 4058 Basel, Switzerland