1. Department of Chemical Sciences, University of Camerino, via S. Agostino 1, I-62032 Camerino (MC), Italy, Department of Organic Chemistry “A. Mangini”, University of Bologna, viale Risorgimento 4, I-40136 Bologna, Italy, and Department of Chemistry, University of Calabria, I-87030 Arcavacata di Rende (CS), Italy enrico.marcantoni@unicam.it