1. Department of Pharmaceutical Biology, Technical University Braunschweig, Mendelssohnstrasse 1, D-38106 Braunschweig, Germany
2. Program for Collaborative Research in the Pharmaceutical Sciences, Department of Medicinal Chemistry and Pharmacognosy, 833 South Wood Street, University of Illinois at Chicago, Chicago, Illinois
3. Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
4. Organic Chemistry Institute, University of Zürich, Winterthurerstrasse 190, CH 8057 Zürich, Switzerland
5. Muséum d'Histoire Naturelle, Case Postale 6434, CH 1211, Genève 6, Switzerland