rac-(9R,10R)-3,6,9,10-Tetrabromo-8,8-dimethyl-9,10-dihydro-2H,8H-pyrano[2,3-f]chromen-2-one (tetrabromoseselin): a photobiochemically active pyranocoumarin

Abstract

The title molecule, C14H10Br4O3, is a tetrabrominated substituted pyranocoumarin synthesized by bromination of seselin (systematic name: 8,8-dimethyl-2H,8H-pyrano[2,3-f]chromene-2-one) isolated from the Indian herbTrachyspermum stictocapum. The pyran ring has a distorted half-chair conformation and its mean plane is inclined to mean plane of the coumarin unit by 3.33 (17)°. In the crystal, molecules are linked by pairs of C—H...O hydrogen bonds, forming inversion dimmers with anR22(16) ring motif. The dimers are linked by pairs of C—H...Br hydrogen bonds, enclosing anR22(16) ring motif, forming chains propagating along the [1-10] direction. Within the chains there are offset π–π interactions involving inversion-related benzene rings with an intercentroid distance of 3.788 (2) Å.