Amino acid-protecting groups.

Albert Isidro-Llobet, Mercedes Álvarez, Fernando Albericio Institute for Research in Biomedicine, Barcelona Science Park, Baldiri Reixac 10, 08028Barcelona, Spain. CIBER-BBN, Networking Centre on Bioengineering, Biomaterials and Nanomedicine, Barcelona Science Park, Baldiri Reixac 10, 08028-Barcelona, Spain. Laboratory of Organic Chemistry, Faculty of Pharmacy, University of Barcelona, 08028Barcelona, Spain. Department of Organic Chemistry, University of Barcelona, Martí i Franqués 1, 08028Barcelona, Spain. E-mail: [email protected]; [email protected] RECEIVED DATE *Authors to whom correspondence should be addressed. Fax: 34 93 403 71 26. E-mail: [email protected]; [email protected];