Crystal structure of a photobiologically active brominated angular pyranocoumarin: bromo-hydroxy-seselin

The title compound, C 14 H 13 BrO 3 [systematic name: rac -(9 S ,10 R )-9-bromo-10-hydroxy-8,8-dimethyl-9,10-dihydro-2 H ,8 H -pyrano[2,3- f ]chromen-2-one], is a substituted pyranocoumarin, obtained by bromination of seselin [8,8-dimethyl-2 H ,8 H -pyrano[2,3- f ]chromen-2-one], which was isolated from the Indian herb Trachyspermum stictocarpum (Aajmod). The pyrano ring has a distorted half-chair conformation and its mean plane is inclined to the coumarin mean plane by 1.6 (2)°. In the crystal, molecules are linked by pairs of O—H...O hydrogen bonds, forming inversion dimers with an R 2 2 (16) ring motif. The dimers stack along the a -axis direction and are linked by offset π–π interactions, forming columns [intercentroid distance = 3.514 (4) Å].