1. Institute of Organic Chemistry, University of Würzburg, Am Hubland 1, Würzburg, Germany
2. International Tomography Center, Institutskaya 3a, Novosibirsk, Russia and Novosibirsk State University, Novosibirsk 630090, Russia
3. Department of Chemistry, University of Konstanz, Universitätsstraße 10, Konstanz, Germany