13C NMR of coumarins. IV—Furanocoumarins

Abstract 13 C NMR data for several linear furanocoumarins are reported. The β, γ syn and δ effects of a 5‐oxygenated function on the coumarinic skeleton were measured. A spectroscopic criterion for distinguishing between C‐5 and C‐8 oxygenated, between C‐5 oxygenated, C‐8 alkylated and C‐5 alkylated, C‐8 oxygenated linear furanocoumarins and between C‐5 oxygenated linear or angular furanocoumarins is proposed.