[1] Department of Chemistry, Brown University, Providence, RI 02912, United States
[2] Department of Organic Chemistry Ugo Schiff, University of Florence, Via G. Capponi 9, I-50121 Florence, Italy
[3] Department of Molecular Pharmacology, Division of Biology and Medicine, Brown University, Providence, RI 02912, United States
[4] Menarini Ricerche, S.p.A, I-50131 Florence, Italy