13C NMR studies of some hydroxycoumarins and related compounds

The ¹³C chemical shifts and one-bond carbon-hydrogen coupling constants have been obtained for some hydroxycoumarins and their corresponding acetoxy and methoxy derivatives. The changes in the one-bond carbon-hydrogen coupling constants resulting from the conversion of a hydroxy group to an acetoxy group represent a simple method of assignment of the ¹³C NMR signals in coumarins which contain one or more hydroxy groups in the benzenoid ring.