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Enhancement of the chiroptical response of α‐amino acids via N ‐substitution for molecular structure determination using vibrational circular dichroism
Author(s) -
Polavarapu Prasad L.,
Santoro Ernesto,
Covington Cody L.,
Raghavan Vijay
Publication year - 2020
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.23205
Subject(s) - conformational isomerism , chemistry , vibrational circular dichroism , circular dichroism , spectral line , crystallography , hydrogen bond , computational chemistry , stereochemistry , molecule , organic chemistry , physics , astronomy
The chiroptical response in the form of vibrational circular dichroism (VCD) in the midinfrared region is found to be enhanced when a hydrogen of amino group of l ‐tryptophan is substituted with acetyl, acryloyl, or maleyl group. The order of preference for VCD enhancement is found to be acryloyl > acetyl > maleyl group. The resulting experimental VCD spectra are also found to be satisfactorily reproduced by the quantum mechanical (QM) predicted spectra. The QM predicted spectra were simulated using the conformer populations, (a) predicted by Gibbs energies and (b) optimized to maximize the similarity between experimental and predicted VCD spectra. It is found that the conformer populations predicted by Gibbs energies do not yield the maximum possible similarity between experimental and the QM predicted spectra. This work identifies the N‐ substitution of α‐amino acids and determining the conformer populations that best reproduce the experimental spectra as two new approaches for molecular structure determination.