1. Department of Chemistry, INSTM RU, University of Florence, via della Lastruccia n. 3, I-50019 Sesto Fiorentino, Italy, Department of Chemical and Biosystems Science and Technology and University Centre of Colle di Val d'Elsa, University of Siena, Via A. Moro 2, I-53100 Siena, Italy, and Department of Organic Chemistry, University of Florence, via della Lastruccia n. 13, I-50019 Sesto Fiorentino, Italy