1. Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Saarland University Campus, 66123 Saarbrücken, Germany
2. Saarland University, Organic Chemistry, Campus Geb. C4.2, 66123 Saarbrücken, Germany
3. Department of Molecular Microbiology, John Innes Centre, Norwich, UK
4. School of Chemistry, University of Glasgow, Glasgow, UK