1. Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet 30, CH-1211 Geneva 4, Switzerland
2. Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. 9, Sofia 1113, Bulgaria
3. Laboratory of Crystallography, University of Geneva, Quai Ernest Ansermet 24, CH-1211 Geneva 4, Switzerland
4. Institute of Mineralogy and Crystallography “Acad. Ivan Kostov”, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. 107, Sofia 1113, Bulgaria
5. Dipartimento di Chimica e Tecnologie del Farmaco, Università “La Sapienza”, 00185 Roma, Italy