¹³C isotope effects on ¹H chemical shifts: NMR spectral analysis of ¹³C-labelled D-glucose and some ¹³C-labelled amino acids

The one‐ and two‐bond ¹³C isotope shifts, typically −1.5 to −2.5 ppb and −0.7 ppb respectively, in non‐cyclic aliphatic systems and up to −4.4 ppb and −1.0 ppb in glucose cause effects that need to be taken into account in the adaptive NMR spectral library‐based quantification of the isotopomer mixtures. In this work, NMR spectral analyses of some ¹³C‐labelled amino acids, D‐glucose and other small compounds were performed in order to obtain rules for prediction of the ¹³C isotope effects on ¹H chemical shifts. It is proposed that using the additivity rules, the isotope effects can be predicted with a sufficient accuracy for amino acid isotopomer applications. For glucose the effects were found strongly non‐additive. The complete spectral analysis of fully ¹³C‐labelled D‐glucose made it also possible to assign the exocyclic proton signals of the glucose.