1. Department
of Biochemistry, University of Lausanne, Chemin de Boveresses 155, 1066 Epalinges, Switzerland
2. Department
of Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
3. Institute
of Organic Chemistry, Albert-Ludwigs University of Freiburg, Albertstrasse 21, 79104 Freiburg, Germany