1. Organic Chemistry, Department of Chemistry, Faculty of Sciences, Universität Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany
2. Laboratory of Virology and Chemotherapy, Department of Microbiology, Immunology and Transplantation, Rega Institute for Medical Research, KU Leuven, Herestraat 49, B-3000 Leuven, Belgium