1. Institute of Organic Chemistry and Biochemistry, Flemingovo nám. 2, 16610 Prague, Czech Republic, Fax: +420‐220 183 462
2. Department of Chemistry, University of Utrecht, Sorbonnelaan 16, 3508 TB Utrecht, Netherlands
3. Department of Organic Chemistry and Nuclear Chemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 12840 Prague, Czech Republic