Alpinumisoflavone.

The title compound, C(20)H(16)O(5), {systematic name: 5-hydr-oxy-7-(4-hydroxy-phen-yl)-2,2-dimethyl-2H,6H-benzo[1,2-b:5,4-b']dipyran-6-one}, was obtained by demethyl-ation of the biologically active related compound, 4-O-methyl-alpinum-iso-flavone. The mol-ecular structure of the title compound is characterized by a fused tricyclic system that contains an approximately planar benzopyrone ring fragment. The six membered pyran ring adopts a half-chair conformation. Both ring systems show an out-of-plane twist. The dihedral angle between the mean plane of the benzopyrone system and the benzene ring is 54.29 (3)°. The mol-ecules are linked by O-H⋯O hydrogen bonds, forming a mol-ecular tape running along the b axis.