1. Dipartimento di Chimica e Chimica IndustrialeUniversity of Pisa via G. Moruzzi 13 56124 Pisa Italy
2. Department of Organic ChemistryUniversity of Geneva Quai Ernest Ansermet 30 1211 Geneva 4 Switzerland
3. Univ. BordeauxBordeaux INPCNRSInstitut des Sciences Moléculaires, UMR 5255 16 avenue Pey-Berland 33607 Pessac France