1. Laboratory of Bioorganic Chemistry, 8 Center Drive, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States
2. Department of Chemistry, Vanderbilt University, 2213 Garland Avenue, Nashville, Tennessee 37235, United States
3. Vanderbilt Institute of Chemical Biology, Vanderbilt University, 7330 Stevenson Center, Nashville, Tennessee 37235, United States
4. Dipartimento di Farmacia, Università di Salerno, via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy