1. Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz,
Germany
2. Faculty of Chemistry
and Pharmacy, Department of Applied Organic Chemistry, University of Sofia, James Bourchier
1, 1164 Sofia,
Bulgaria
3. Department
of Chemistry, University of Leuven, Celestijnenlaan
200D, B-3001 Leuven, Belgium
4. Laboratoire de Chimie
Théorique, Facultés Universitaires Notre-Dame de la Paix, rue de Bruxelles, 61, B-5000
Namur, Belgium
5. Institute
of Organic Chemistry
with Centre of Phytochemisty, Bulgarian Academy of Sciences, Sofia, 1113 Bulgaria