1. Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich, Switzerland
2. Biochemisches
Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
3. Beckman Institute, and Division of Chemistry and Chemical
Engineering, California Institute of Technology, M/C 139-74, Pasadena, California 91125, United States