1. Department of Organic Chemistry, Faculty of Chemical Technology, University of Pardubice, Nám Čs. Legií 565, CZ-532 10 Pardubice, Czech Republic, Dipartimento di Chimica and Centro di Strutturistica Diffrattometrica, Università di Ferrara, Via L. Borsari 46, I-441 00 Ferrara, Italy, and Research Institute for Organic Syntheses (VUOS), Rybitví 296, CZ-532 18 Pardubice 20, Czech Republic