1. Laboratory
of Organic Chemistry, Department of Chemistry, University of Helsinki, A. I. Virtasen aukio 1, P.O. Box 55, University
of Helsinki FIN-00014, Finland
2. Institute for Research in Biomedicine (IRB Barcelona), Baldiri Reixac, 10, Barcelona 08028, Spain
3. Departament
de Química Orgànica, Universitat de Barcelona, Martí
i Franquès, 1-11, Barcelona 08028, Spain