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Volume 30
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10.3390/molecules30030597
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This is an early access version, the complete PDF, HTML, and XML versions will be available soon.
Article

Complete Assignments of 1H and 13C NMR Chemical Shift Changes Observed upon Protection of Hydroxy Group in Borneol and Isoborneol and Their DFT Verification

by
Baohe Lyu
1,
Yoshikazu Hiraga
1,*,
Ryukichi Takagi
2 and
Satomi Niwayama
3,*
1
Graduate School of Science and Technology, Hiroshima Institute of Technology, 2-1-1 Miyake, Saeki-ku, Hiroshima 731-5193, Japan
2
Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan
3
Graduate School of Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran 050-8585, Japan
*
Authors to whom correspondence should be addressed.
Molecules 2025, 30(3), 597; https://doi.org/10.3390/molecules30030597
Submission received: 25 December 2024 / Revised: 23 January 2025 / Accepted: 24 January 2025 / Published: 28 January 2025
(This article belongs to the Special Issue Applications of NMR Spectroscopy to Problem Solving for Inorganic, Organometallic, and Organic Compounds)
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Abstract

Complete assignments of the 1H and 13C NMR chemical shifts for the monoterpenes, borneol 1a and isoborneol 2a, as well as their derivatives (1b–1g and 2b–2g), in which the secondary hydroxy group is protected with various protecting groups, have been made in various solvents. Upon protection of the hydroxy groups in 1a and 2a, many protons and carbons within the bicyclic ring exhibited downfield or upfield shifts in their chemical shift values, facilitating the unambiguous assignments of these protons and carbons. These chemical shift values also showed excellent correlations with those obtained from density functional theory (DFT) calculations. Furthermore, the anisotropic effect of the benzene ring was estimated by the analysis of the iso-chemical shielding surface (ICSS) resulting from substituents introduced to the hydroxyl groups of 1a and 2a.
Keywords: NMR assignment; chemical shift change; DFT calculations; iso-chemical shielding surface; anisotropic effect NMR assignment; chemical shift change; DFT calculations; iso-chemical shielding surface; anisotropic effect
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MDPI and ACS Style

Lyu, B.; Hiraga, Y.; Takagi, R.; Niwayama, S. Complete Assignments of 1H and 13C NMR Chemical Shift Changes Observed upon Protection of Hydroxy Group in Borneol and Isoborneol and Their DFT Verification. Molecules 2025, 30, 597. https://doi.org/10.3390/molecules30030597

AMA Style

Lyu B, Hiraga Y, Takagi R, Niwayama S. Complete Assignments of 1H and 13C NMR Chemical Shift Changes Observed upon Protection of Hydroxy Group in Borneol and Isoborneol and Their DFT Verification. Molecules. 2025; 30(3):597. https://doi.org/10.3390/molecules30030597

Chicago/Turabian Style

Lyu, Baohe, Yoshikazu Hiraga, Ryukichi Takagi, and Satomi Niwayama. 2025. "Complete Assignments of 1H and 13C NMR Chemical Shift Changes Observed upon Protection of Hydroxy Group in Borneol and Isoborneol and Their DFT Verification" Molecules 30, no. 3: 597. https://doi.org/10.3390/molecules30030597

APA Style

Lyu, B., Hiraga, Y., Takagi, R., & Niwayama, S. (2025). Complete Assignments of 1H and 13C NMR Chemical Shift Changes Observed upon Protection of Hydroxy Group in Borneol and Isoborneol and Their DFT Verification. Molecules, 30(3), 597. https://doi.org/10.3390/molecules30030597

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