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Taniguchi T, Agbo DO. Vibrational circular dichroism spectroscopy in the C-D, XY, and XYZ stretching region. Phys Chem Chem Phys 2023; 25:28567-28575. [PMID: 37861094 DOI: 10.1039/d3cp04287a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
Vibrational circular dichroism (VCD) spectroscopy is a powerful technique for structural analysis of chiral molecules, but information available from VCD spectra of large molecular systems can be limited by severe overlap of vibrational bands. While common chiral molecules do not absorb in the 1900-2400 cm-1 region, observation of VCD signals in this spectrally-isolated region is possible for molecules containing C-D, XY, and XYZ chromophores. Thus, a strategic introduction of these chromophores to a target molecule may produce VCD signals informative for molecular structures. VCD spectroscopy in the 1900-2400 cm-1 region is a rather unexplored research field and its basic properties remain to be investigated. This perspective article discusses insight obtained so far on the usefulness and physicochemical aspects of VCD spectroscopy in this region with briefly summarizing previous experimental VCD studies including classic examples as well as our recent results. We show that anharmonic effects such as overtones and combination bands often complicate VCD patterns. On the other hand, some molecules exhibit characteristic VCD signals that can be well interpreted by harmonic DFT spectral calculations for structural analysis. This article also discusses several examples of the use of this region for studying solute-solvent interactions and for VCD signal augmentation.
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Affiliation(s)
- Tohru Taniguchi
- Frontier Research Center for Advanced Material and Life Science, Faculty of Advanced Life Science, Hokkaido University, North 21 West 11, Sapporo 001-0021, Japan.
| | - Davidson Obinna Agbo
- Graduate School of Life Science, Hokkaido University, North 21 West 11, Sapporo 001-0021, Japan
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Zubir MZM, Maulida NF, Abe Y, Nakamura Y, Abdelrasoul M, Taniguchi T, Monde K. Deuterium labelling to extract local stereochemical information by VCD spectroscopy in the C-D stretching region: a case study of sugars. Org Biomol Chem 2022; 20:1067-1072. [PMID: 35019932 DOI: 10.1039/d1ob02317a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Stereochemical elucidation of molecules with multiple chiral centers is difficult. Even with VCD spectroscopy, excluding all but one diastereomeric structural candidate is challenging because the stereochemical inversion of one chiral center among many centers does not always result in noticeable differences in their VCD spectra. This work demonstrates that the introduction of a suitable VCD chromophore with absorption in the 2300-1900 cm-1 region can be used for extracting local stereochemical information and for the stereochemical assignment of the C-1 position of various sugars as a case study. Through studies on a series of epimeric pairs of monosaccharides and their derivatives, we found that the introduction of one -OCD3 group to each C-1 position produced almost mirror-image VCD patterns in the 2300-1900 cm-1 region depending on the C-1 stereochemistry irrespective of the other molecular moieties. This work also shows that comparison of the observed VCD signals and the calculated ones enables the stereochemical assignment of a chiral center in the vicinity of the chromophore. This study provides a proof of concept that the use of a VCD chromophore in the 2300-1900 cm-1 region enables the analysis of selected stereochemistry of suitable molecular systems. Further studies on this concept should lead to the development of a method useful for the structural elucidation of other types of complex molecules.
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Affiliation(s)
| | - Nurul Fajry Maulida
- Graduate School of Life Science, Hokkaido University, Kita 21 Nishi 11, Sapporo 001-0021, Japan
| | - Yoshihiro Abe
- Graduate School of Life Science, Hokkaido University, Kita 21 Nishi 11, Sapporo 001-0021, Japan
| | - Yuta Nakamura
- Graduate School of Life Science, Hokkaido University, Kita 21 Nishi 11, Sapporo 001-0021, Japan
| | - Mariam Abdelrasoul
- Graduate School of Life Science, Hokkaido University, Kita 21 Nishi 11, Sapporo 001-0021, Japan.,Department of Medicinal Chemistry, Faculty of Pharmacy, Assiut University, Assiut 71526, Egypt
| | - Tohru Taniguchi
- Frontier Research Center for Advanced Material and Life Science, Faculty of Advanced Life Science, Hokkaido University, Kita 21 Nishi 11, Sapporo 001-0021, Japan.
| | - Kenji Monde
- Frontier Research Center for Advanced Material and Life Science, Faculty of Advanced Life Science, Hokkaido University, Kita 21 Nishi 11, Sapporo 001-0021, Japan.
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