Rotational isomerism has been observed on some C-glycosyl flavonoids with special chemical strutures. It may bring rotamers arising from restricted rotation about one single bond. C-glycosyl flavonoids showed a wide range of biological activities. This emphasizes the significance to understand the conformational stability of C-glycosyl flavonoids in drug development. Three C-glycosyl flavonoids, vaccarin (1), isovitexin-2”-O-arabinoside (2) and spinosin (3), were found to exist as rotamers in the light of their featured behavior in nuclear magnetic resonance spectroscopy (NMR). Some separated signals were observed in their 1H-NMR and 13C NMR spectra. Variable-temperature (VT) 1H-NMR experiments were then conducted to study the observation and to determine their rotational energy barriers and then evaluate their conformational stability. The temperature varied from 298K to 363K and separated signals merged at high temperature. With the help of Eyring equation, the rotational energy barriers of compounds 1-3 were calculated and found much lower than 24 kcal/mol. When the energy barrier is high enough (> 24 kcal/mol) and the time scale for interconversion (halflife > 1000 s) is long enough for isolation of individual rotamers, the isomers are termed atropisomers, which thus will display axial charity. According to this standard, the compounds 1-3 may not exhibit atropisomerism and isolation of rotamers should be difficult. Their relatively low energy barriers indicate they can be developed as rapidly equilibrating mixture.
| Published in | Modern Chemistry (Volume 9, Issue 1) |
| DOI | 10.11648/j.mc.20210901.12 |
| Page(s) | 8-12 |
| Creative Commons |
This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited. |
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Copyright © The Author(s), 2021. Published by Science Publishing Group |
Rotamer, Atropisomer, Rotational Isomerism, C-glycosyl Flavonoids, VT-NMR
| [1] | LaPlante, S. R., Fader, L. D., Fandrick, K. R., Fandrick, D. R., Hucke, O., Kemper, R., Miller, S. P. F., Edwards, P. J., 2011a. Assessing atropisomer axial chirality in drug discovery and development. J. Med. Chem. 54, 7005-7022. |
| [2] | LaPlante, S. R., Edwards, P. J., Fader, L. D., Jakalian, A., Hucke, O., 2011b. Revealing atropisomer axial chirality in drug discovery. ChemMedChem 6, 505-13. |
| [3] | Kumarasamy, E., Raghunathan, R., Sibi, M. P., Sivaguru, J., 2015. Nonbiaryl and heterobiaryl atropisomers: molecular templates with promise for atropselective chemical transformations. Chem. Rev. 20, 11239-11300. |
| [4] | Zhou, G. H., Yan, R. L., Wang, X. G., Li, S. L., Lin, J., Liu, J., Zhao, Z. D., 2019. The overlooked rotational isomerism of C-glycosyl flavonoids. Phytochem. Rev. 18, 443-461. |
| [5] | Xiao, J., Capanoglu E., Jassbi, A. R. Miron, A., 2016. Advance on the flavonoid c-glycosides and health benefits. Crit. Rev. Food Sci. Nutr. 56, S29-45. |
| [6] | Glunz, P. W., 2018. Recent encounters with atropisomerism in drug discovery. Bioorg. & Med. Chem. Lett. 53-60. |
| [7] | Toenjes, S. T., Gustafson J. L., 2018. Atropisomerism in medicinal chemistry: challenges and opportunities. Fut. Med. Chem. 10, 409. |
| [8] | Zhou, G. H., Wu, H. W., Wang, T., Guo, R. X., Xu, J., Zhang, Q., Tang, L. Y., Wang, Z. J., 2017. C-glycosylflavone with rotational isomers from Vaccaria hispanica (Miller) Rauschert seeds. Phytochem. Lett. 19, 241-247. |
| [9] | Berber, H., Lameiras, P., Clement, D., Cyril, A., Jonathan, C., 2014. Atropisomerism about aryl–Csp3 bonds: the electronic and steric influence of ortho -substituents on conformational exchange in cannabidiol and linderatin derivatives. J. Org. Chem. 79, 6015-6027. |
| [10] | Frank, J. H., Powder-George, Y. L., Ramsewak, R. S., Reynolds, W. F., 2012. Variable-temperature 1H-NMR studies on two C-glycosylflavones. Molecules 17, 7914-7926. |
| [11] | Liu, X., Shi, Y., Hu, H., et al., 2018. Three new C -glycosyflavones with acetyl substitutions from Swertia mileensis. J. Nat. Med. 72. |
| [12] | Jing, L., Liu, Y., Zhong, D., et al., 2017. Structural and quantitative analysis of three C-glycosylflavones by variable temperature proton quantitative nuclear magnetic resonance. Journal of Analytical Methods in Chemistry 2017, 1-5. |
| [13] | Murai, Y., Kitajima, J., Iwashina, T., 2019. C-glycosylflavones from the leaves and flowers of gentiana algida in Japan. Bulletin of the National Museum of Nature and Science 45, 87-92. |
| [14] | Olennikov, D. N., 2020. Silenerepin-a new C-glycosylflavone from Silene repens. Chem. Nat. Compd. 56, 423–426. |
| [15] | Olennikov, D. N., Chirikova, N. K., 2019. C-glycosyl flavones from two eastern siberian species of silene. Chem. Nat. Compd. 55, 642–647. |
APA Style
Guohong Zhou, Renliang Yan. (2021). Variable-temperature 1H-NMR Studies on Three C-glycosylflavones Exhibiting Rotational Isomerism. Modern Chemistry, 9(1), 8-12. https://doi.org/10.11648/j.mc.20210901.12
ACS Style
Guohong Zhou; Renliang Yan. Variable-temperature 1H-NMR Studies on Three C-glycosylflavones Exhibiting Rotational Isomerism. Mod. Chem. 2021, 9(1), 8-12. doi: 10.11648/j.mc.20210901.12
AMA Style
Guohong Zhou, Renliang Yan. Variable-temperature 1H-NMR Studies on Three C-glycosylflavones Exhibiting Rotational Isomerism. Mod Chem. 2021;9(1):8-12. doi: 10.11648/j.mc.20210901.12
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Download@article{10.11648/j.mc.20210901.12,
author = {Guohong Zhou and Renliang Yan},
title = {Variable-temperature 1H-NMR Studies on Three C-glycosylflavones Exhibiting Rotational Isomerism},
journal = {Modern Chemistry},
volume = {9},
number = {1},
pages = {8-12},
doi = {10.11648/j.mc.20210901.12},
url = {https://doi.org/10.11648/j.mc.20210901.12},
eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.mc.20210901.12},
abstract = {Rotational isomerism has been observed on some C-glycosyl flavonoids with special chemical strutures. It may bring rotamers arising from restricted rotation about one single bond. C-glycosyl flavonoids showed a wide range of biological activities. This emphasizes the significance to understand the conformational stability of C-glycosyl flavonoids in drug development. Three C-glycosyl flavonoids, vaccarin (1), isovitexin-2”-O-arabinoside (2) and spinosin (3), were found to exist as rotamers in the light of their featured behavior in nuclear magnetic resonance spectroscopy (NMR). Some separated signals were observed in their 1H-NMR and 13C NMR spectra. Variable-temperature (VT) 1H-NMR experiments were then conducted to study the observation and to determine their rotational energy barriers and then evaluate their conformational stability. The temperature varied from 298K to 363K and separated signals merged at high temperature. With the help of Eyring equation, the rotational energy barriers of compounds 1-3 were calculated and found much lower than 24 kcal/mol. When the energy barrier is high enough (> 24 kcal/mol) and the time scale for interconversion (halflife > 1000 s) is long enough for isolation of individual rotamers, the isomers are termed atropisomers, which thus will display axial charity. According to this standard, the compounds 1-3 may not exhibit atropisomerism and isolation of rotamers should be difficult. Their relatively low energy barriers indicate they can be developed as rapidly equilibrating mixture.},
year = {2021}
}
TY - JOUR T1 - Variable-temperature 1H-NMR Studies on Three C-glycosylflavones Exhibiting Rotational Isomerism AU - Guohong Zhou AU - Renliang Yan Y1 - 2021/04/16 PY - 2021 N1 - https://doi.org/10.11648/j.mc.20210901.12 DO - 10.11648/j.mc.20210901.12 T2 - Modern Chemistry JF - Modern Chemistry JO - Modern Chemistry SP - 8 EP - 12 PB - Science Publishing Group SN - 2329-180X UR - https://doi.org/10.11648/j.mc.20210901.12 AB - Rotational isomerism has been observed on some C-glycosyl flavonoids with special chemical strutures. It may bring rotamers arising from restricted rotation about one single bond. C-glycosyl flavonoids showed a wide range of biological activities. This emphasizes the significance to understand the conformational stability of C-glycosyl flavonoids in drug development. Three C-glycosyl flavonoids, vaccarin (1), isovitexin-2”-O-arabinoside (2) and spinosin (3), were found to exist as rotamers in the light of their featured behavior in nuclear magnetic resonance spectroscopy (NMR). Some separated signals were observed in their 1H-NMR and 13C NMR spectra. Variable-temperature (VT) 1H-NMR experiments were then conducted to study the observation and to determine their rotational energy barriers and then evaluate their conformational stability. The temperature varied from 298K to 363K and separated signals merged at high temperature. With the help of Eyring equation, the rotational energy barriers of compounds 1-3 were calculated and found much lower than 24 kcal/mol. When the energy barrier is high enough (> 24 kcal/mol) and the time scale for interconversion (halflife > 1000 s) is long enough for isolation of individual rotamers, the isomers are termed atropisomers, which thus will display axial charity. According to this standard, the compounds 1-3 may not exhibit atropisomerism and isolation of rotamers should be difficult. Their relatively low energy barriers indicate they can be developed as rapidly equilibrating mixture. VL - 9 IS - 1 ER -
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