Employing VCD spectroscopy, we demonstrate that the structural behaviour of the oligomers Boc-(L-Phe-L-Oxd)n-OBn are similar from n = 2 to n = 6; ab-initio calculations for the n=1 case provide physical insight into the conformational properties. Further information is gained by IR, 1H NMR and ECD spectroscopies; ECD spectra suggests the presence of different conformations between n = 1, on one side, and longer chain foldamers, on the other side. VCD and absorption IR spectra in methanol solutions can be interpreted as indicative of a PPII structure. In the case of Boc-L-Phe-L-Oxd-OBn, VCD spectra in CCl4 and detailed DFT computational analysis, allow one to demonstrate that the most populated conformers exhibit backbone dihedral angles similar to those of a PPII geometry. This is a remarkable outcome, as we had previously demonstrated that the Boc-(L-Ala-D-Oxd)n-OBn series folds in a band ribbon spiral, that is a subtype of the 310 helix.

Conformational Studies of Phe-rich foldamers by VCD spectroscopy and ab-initio calculations

CASTELLUCCI, NICOLA;SABATINO, PIERA;TOMASINI, CLAUDIA
2012

Abstract

Employing VCD spectroscopy, we demonstrate that the structural behaviour of the oligomers Boc-(L-Phe-L-Oxd)n-OBn are similar from n = 2 to n = 6; ab-initio calculations for the n=1 case provide physical insight into the conformational properties. Further information is gained by IR, 1H NMR and ECD spectroscopies; ECD spectra suggests the presence of different conformations between n = 1, on one side, and longer chain foldamers, on the other side. VCD and absorption IR spectra in methanol solutions can be interpreted as indicative of a PPII structure. In the case of Boc-L-Phe-L-Oxd-OBn, VCD spectra in CCl4 and detailed DFT computational analysis, allow one to demonstrate that the most populated conformers exhibit backbone dihedral angles similar to those of a PPII geometry. This is a remarkable outcome, as we had previously demonstrated that the Boc-(L-Ala-D-Oxd)n-OBn series folds in a band ribbon spiral, that is a subtype of the 310 helix.
JOURNAL OF ORGANIC CHEMISTRY
G. Longhi; S. Abbate; F. Lebon; N. Castellucci; P. Sabatino; C. Tomasini
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/121562
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