A New Metric for Evaluating DFT Calculated Proton and Carbon Chemical Shifts of Natural Products and Organic Compounds

The calculation of DFT (density functional theory) chemical shifts have become an important technique for the verification of a proposed structure. An easily calculated metric developed for proton and carbon chemical shifts of natural products and organic compounds, the calculated chemical shift index (CCSI), has been developed, which uses the deviation of each pair of calculated and experimental chemical shifts. The mean absolute deviation (MAD), which is commonly used as the goodness of fit metric for DFT calculated chemical shifts, can conceal large deviations in the calculated data. A classification strategy is also proposed for the CCSI to highlight when further assessment of the NMR data is required.

Automated summary

The calculation of DFT chemical shifts is crucial for verifying proposed structures, with the CCSI serving as a metric to measure deviations between calculated and experimental chemical shifts. While MAD is commonly used as a goodness of fit metric, it may mask large deviations in the data. A classification strategy for CCSI is also proposed to indicate when further evaluation of NMR data is needed.