1. Organic Chemistry; Saarland University; Campus C4.2 66123 Saarbrücken Germany
2. Department Microbial Natural Products; Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS); Saarland University; Campus E8.1 66123 Saarbrücken Germany
3. Department of Pharmacy, Pharmaceutical Biology; Ludwig-Maximilians-University Munich); Butenandtstr. 5-13 81377 München Germany