Vibrational circular dichroism as a probe of solid-state organisation of derivatives of cyclic ß-amino acids: Cis- and trans-2-aminocyclobutane-1-carboxylic acid.
Chirality
; 31(8): 547-560, 2019 08.
Article
en En
| MEDLINE
| ID: mdl-31241803
ABSTRACT
Peptide models built from cis- and trans-2-aminocyclobutane-1-carboxylic acids (ACBCs) are studied in the solid phase by combining Fourier-transform infrared spectroscopy (FTIR) absorption spectroscopy, vibrational circular dichroism (VCD), and quantum chemical calculations using density functional theory (DFT). The studied systems are N-tert-butyloxycarbonyl (Boc) derivatives of 2-aminocyclobutanecarboxylic acid (ACBC) benzylamides, namely Boc-(cis-ACBC)-NH-Bn and Boc-(trans-ACBC)-NH-Bn. These two diastereomers show very different VCD signatures and intensities, which of the trans-ACBC derivative being one order of magnitude larger in the region of the ν (CO) stretch. The spectral signature of the cis-ACBC derivative is satisfactorily reproduced by that of the monomer extracted from the solid-state geometry of related ACBC derivatives, which shows that no long-range effects are implicated for this system. In terms of hydrogen bonds, the geometry of this monomer is intermediate between the C6 and C8 structures (exhibiting a 6- or 8-membered cyclic NHâ¯O hydrogen bond) previously evidenced in the gas phase. The benzyl group must be in an extended geometry to reproduce satisfactorily the shape of the VCD spectrum in the ν (CO) range, which qualifies VCD as a potential probe of dispersion interaction. In contrast, reproducing the IR and VCD spectrum of the trans-ACBC derivative requires clusters larger than four units, exhibiting strong intermolecular H-bonding patterns. A qualitative agreement is obtained for a tetramer, although the intensity enhancement is not reproduced. These results underline the sensitivity of VCD to the long-range organisation in the crystal.
Palabras clave
Texto completo:
1
Base de datos:
MEDLINE
Asunto principal:
Aminoácidos Cíclicos
Tipo de estudio:
Qualitative_research
Idioma:
En
Revista:
Chirality
Asunto de la revista:
BIOLOGIA MOLECULAR
/
QUIMICA
Año:
2019
Tipo del documento:
Article