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Synthesis, conformational study, and spectroscopic characterization of the cyclic C α,α ‐disubstituted glycine 9‐amino‐9‐fluorenecarboxylic acid
Author(s) -
Savrda Jaroslav,
Mazaleyrat JeanPaul,
Wakselman Michel,
Formaggio Fernando,
Crisma Marco,
Toniolo Claudio
Publication year - 1999
Publication title -
journal of peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 66
eISSN - 1099-1387
pISSN - 1075-2617
DOI - 10.1002/(sici)1099-1387(199902)5:2<61::aid-psc173>3.0.co;2-4
Subject(s) - dipeptide , pentamer , chemistry , residue (chemistry) , peptide , cyclic peptide , stereochemistry , amino acid , crystal structure , crystallography , organic chemistry , biochemistry
A series of terminally blocked peptides (to the pentamer level) from l ‐Ala and the cyclic C α , α ‐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 α,α ‐disubstituted Gly residues Ac 5 c and Dϕg 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 α,α ‐disubstituted Gly residue is also reported. Copyright © 1999 European Peptide Society and John Wiley & Sons, Ltd.