Theoretical prediction and assignment of vicinal 1H-1H coupling constants of diastereomeric 3-alkoxy-6,7-epoxy-2-oxabicyclo[3.3.0]octanes

• Published in: Magnetic resonance in chemistry Vol. 49; no. 2; pp. 76 - 82
• Main Authors: Aav, Riina, Pehk, Tõnis, Tamp, Sven, Tamm, Toomas, Kudrjašova, Marina, Parve, Omar, Lopp, Margus
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-02-2011
• Subjects: 13C; 3J(H; 3J(H,H) coupling constants; computational chemistry; Constants; Coupling (molecular); Deviation; five-membered rings; H) coupling constants; Joining; Mathematical analysis; NMR; Optimization; Quantum chemistry; relative configuration; Spin-spin coupling
• ISSN: 0749-1581; 1097-458X; 1097-458X
• DOI: 10.1002/mrc.2712

Spin–spin coupling constants between nuclei in NMR spectroscopy reflect their spatial arrangement. A number of calculation methods, applying different levels of theory, have been developed to support the stereochemical assignment of novel compounds. Nevertheless, revisions of the assignment of structures in the literature are not rare. In the present work, the reliability of the calculation methods amenable for a theoretical prediction of spin–spin coupling constants of vicinal protons to support correct stereochemical assignment of substitution at five‐membered rings of 3‐alkoxy‐6,7‐epoxy‐2‐oxabicyclo[3.3.0]octanes was studied. Experimental 3J(H,H) coupling constants were compared with the coupling constants calculated for all possible diastereomers. The fully quantum chemical approach provided theoretical 3J(H,H) coupling constants with an absolute deviation of no more than 1.1 Hz for 91% of the experimentally studied coupled spins, whereas the methods without quantum chemical geometry optimization resulted in completely unreliable predictions. Consequently, for a reliable stereochemical assignment of small and medium size molecules, the protocol for calculating the coupling constants based on the results of the quantum chemical geometry optimization is recommended. Copyright © 2011 John Wiley & Sons, Ltd.
The usefulness of various calculation methods amenable for a theoretical prediction of spin–spin coupling constants of vicinal protons to support the correct stereochemical assignment of substitution at five‐membered rings was studied on the example of vicinal 1H1H spin–spin coupling constants of 3‐alkoxy‐6,7‐epoxy‐2‐oxabicyclo[3.3.0]octanes.