1. University of Kaiserslautern, Paul-Ehrlich-Str. 23, D-67663 Kaiserslautern, Germany
2. Institute of Organic Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany
3. Institute of Organic Chemistry, University of Mainz, Duesbergweg 10 – 14, D-55128 Mainz, Germany
4. Institute of Biotechnology and Drug Research, Erwin-Schrödinger-Str. 56, D-67663 Kaiserslautern, Germany