Synthesis, conformational study, and spectroscopic characterization of the cyclic Cα,α-disubstituted glycine 9-amino-9-fluorenecarboxylic acid

✍ Scribed by Jaroslav Savrda; Jean-Paul Mazaleyrat; Michel Wakselman; Fernando Formaggio; Marco Crisma; Claudio Toniolo

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 173 KB
• Volume: 5
• Category: Article
• ISSN: 1075-2617
• DOI: 10.1002/(sici)1099-1387(199902)5:2<61::aid-psc173>3.0.co;2-4

✦ Synopsis

A series of terminally blocked peptides (to the pentamer level) from L-Ala and the cyclic C h,h -disubstituted Gly residue Afc and one Gly/Afc dipeptide have been synthesized by solution method and fully characterized. The molecular structure of the amino acid derivative Boc-Afc-OMe and the dipeptide Boc-Afc-Gly-OMe were determined in the crystal state by X-ray diffraction. In addition, the preferred conformation of all of the model peptides was assessed in deuterochloroform solution by FT-IR absorption and 1 H-NMR. The experimental data favour the conclusion that the Afc residue tends to adopt either the fully-extended (C 5 ) or a folded/helical structure. In particular, the former conformation is highly populated in solution and is also that found in the crystal state in the two compounds investigated. A comparison with the structural propensities of the strictly related C h,h -disubstituted Gly residues Ac 5 c and DFg is made and the implications for the use of the Afc residue in conformationally constrained analogues of bioactive peptides are briefly examined. A spectroscopic (UV absorption, fluorescence, CD) characterization of this novel aromatic C h,h -disubstituted Gly residue is also reported.