1. Institute of Organic Chemistry
2. Technische Universität Braunschweig
3. D-38106 Braunschweig
4. Germany
5. Department for Microbial Natural Products
6. Helmholtz Institute for Pharmaceutical Research Saarland (HIPS)
7. Helmholtz Center for Infection Research and Department of Pharmacy at Universität des Saarlandes
8. D-66123 Saarbrücken