1. Organic Chemistry Department of Chemistry Faculty of Mathematics Informatics and Natural Sciences Universität Hamburg Martin-Luther-King-Platz 6 D-20146 Hamburg Germany
2. Laboratory of Virology and Chemotherapy Department of Microbiology and Immunology and Transplantation Rega Institute for Medical Research, KU Leuven Herestraat 49 B-3000 Leuven Belgium
3. Centre for Structural Systems Biology (CSSB) Hamburg, Deutsches Elektronen-Synchrotron (DESY)-Campus Notkestrasse 85 D-22607 Hamburg Germany