Enhancing the utility of 1JCH coupling constants in structural studies through optimized DFT analysis.

Commonly used DFT methods for the calculation of ¹J_CH coupling constants have typically required the application of ad hoc correction factors, modification of functionals, or empirical scaling to improve the fit between predicted and experimental values. Here we demonstrate that highly accurate ¹J_CH coupling predictions can be obtained without such adjustments by careful selection of DFT methods for geometry optimization and J-coupling calculations (e.g. B3LYP/6-31G(d,p)(mixed)//mPW1PW/cc-pVTZ). The proposed method was cross-validated against a diverse set of 122 ¹J_CH couplings and was successfully applied to the conformational and stereochemical analysis of strychnine and a previously unreported trachylobane diterpene natural product. [ABSTRACT FROM AUTHOR]