title: Absolute configuration of a cyclic dipeptide reflected in vibrational optical activity: ab initio and experimental investigation.
abstract: The ability of Raman optical activity (ROA) and vibrational circular dichroism (VCD) experiments to determine the absolute configuration of chiral molecules with multiple stereogenic centers was explored for four diastereoisomers of a conformationally flexible cyclic dipeptide, cyclo(Arg-Tyr(OMe)). The reliability of the interpretation depended on the correct description of the molecular conformation, which was found to be strongly affected by intramolecular interactions. In particular, when dispersion corrections were included in the density functional theory calculations, the simulated spectra matched the experimental observations well. Experimental and theoretical ROA and VCD spectra were well correlated for all the absolute configurations (RS, SR, SS, and RR) of protonated cyclo(Arg-Tyr(OMe)). These spectroscopies thus appear useful not only for reliable determination of the absolute configuration and conformation but also in revealing the role of hydrogen bonds and C-H···π interactions in the structure stabilization, which can potentially be used when designing enzyme inhibitors and supramolecular architectures.
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø, N-9037 Tromsø, Norway.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Li
authors.forename: Kathrin H
authors.initials: KH
authors.lastname: Hopmann
authors.forename: Jana
authors.initials: J
authors.lastname: Hudecová
authors.forename: Wenche
authors.initials: W
authors.lastname: Stensen
authors.forename: Jana
authors.initials: J
authors.lastname: Novotná
authors.forename: Marie
authors.initials: M
authors.lastname: Urbanová
authors.forename: John-Sigurd
authors.initials: JS
authors.lastname: Svendsen
authors.forename: Petr
authors.initials: P
authors.lastname: Bouř
authors.forename: Kenneth
authors.initials: K
authors.lastname: Ruud
mesh_terms: D002942:Circular Dichroism; D015394:Molecular Structure; D010456:Peptides, Cyclic / Q000737:chemistry*; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D010456:Peptides, Cyclic