1. Department of Chemistry University of Munich Butenandtstrasse 5–13, Haus F 81377 Munich Germany
2. Department of Chemistry New York University 100 Washington Square East, Room 712 New York NY 10003 USA
3. Department of Microbial Natural Products Helmholtz Institute for Pharmaceutical Research Saarland Helmholtz Center for Infection Research Saarland University 66123 Saarbrücken Germany