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

Abstract

The title compound, C14H13BrO3 [systematic name: rac-(9S,10R)-9-bromo-10-hydroxy-8,8-dimethyl-9,10-dihydro-2H,8H-pyrano[2,3-f]chromen-2-one], is a substituted pyranocoumarin, obtained by bromination of seselin [8,8-dimethyl-2H,8H-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 R22(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].

Keywords

• crystal structure
• seselin
• bromination
• hydrogen bonding
• offset π–π interactions