1. Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01‐224 Warsaw (Poland), Fax: (+48) 226326681
2. Université de Bordeaux, ISM (UMR5255 CNRS), F 33400, Bordeaux (France)
3. Warsaw University of Technology, Faculty of Chemistry, Noakowskiego 3, 00‐664 Warsaw (Poland)