1. Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, Beutenberg Campus, 07745 Jena, Germany, University of Würzburg, Institute of Organic Chemistry, Am Hubland, 97074 Würzburg, Germany, and USR CNRS-Pierre Fabre No. 3388 ETaC, Center of Research and Development of Pierre Fabre, 3 avenue Hubert Curien, 31035 Toulouse Cedex 01, France