Natural abundance 17 O NMR spectra of coumarins, furocoumarins and related compounds

The 54.2 MHz 17 O NMR spectra of a series of naturally occurring coumarins and furocoumarins and those of a number of related model compounds are described. The 17 O chemical shifts of the furocoumarins can be predicted by the evaluation of the data of substructures in model compounds. syn ‐Periplanar γ‐ and long‐range interaction effects can be interpreted in terms of steric and electronic effects.