1. Karlsruhe Institute of Technology; Institute of Organic Chemistry; Fritz-Haber-Weg 6 76131 Karlsruhe Germany
2. Department of Chemistry; University of Helsinki; P.O. Box 55 (A.I. Virtasen aukio 1), FIN- 00014 University of Helsinki Finland
3. Karlsruhe Institute of Technology; Institute of Toxicology and Genetics; Hermann-von-Helmholtz-Platz 1, D- 76344 Eggenstein-Leopoldshafen Germany