1. Department of Pharmaceutical Sciences, University of Salerno, I-84084 Fisciano, Italy, Department of Pharmaceutical and Toxicological Chemistry, University of Naples “Federico II”, I-80131 Naples, Italy, Laboratory of Peptide and Protein Chemistry and Biology, University of Florence, I-50019 Sesto Fiorentino, Italy, and Department of Chemistry, University of Naples “Federico II”, I-80126 Naples, Italy