The dihydropyrone structure XVII was supported by a negative enol test with methanolic ferric chloride and by nmr spectrum. This spectrum showed a multiplet of peaks between 7.1 and 8.0 ppm (15 protons) for the aromatic protons, a singlet at 5.88 ppm (one proton) slightly split for the vinyl proton, a quartet centered at 3.22 ppm (one proton) for the tertiary proton, a multiplet centered at 1.42 ppm (two protons) for the methylene group, and a triplet (three ...
