1. Department of Chemistry of Natural Products, University of Naples Federico II, Via D. Montesano 49, 80131 Naples, Italy, Department of Experimental Pharmacology, University of Naples Federico II, Via D. Montesano 49, 80131 Naples, Italy, and Department of Organic Chemistry, University of Palermo, Viale delle Scienze, Parco d’Orleans II, 90128 Palermo, Italy