Crystal structure of dibromomethoxyseselin (DBMS), a photobiologically active pyranocoumarin

Abstract

The title compound, C15H14Br2O4 [systematic name: rac-(9S,10R)-3,9-dibromo-10-methoxy-8,8-dimethyl-9,10-dihydropyrano[2,3-h]chromen-2(8H)-one], is a pyranocoumarin derivative formed by the bromination of seselin, which is a naturally occurring angular pyranocoumarin isolated from the Indian herb Trachyspermum stictocarpum. In the molecule, the benzopyran ring system is essentially planar, with a maximum deviation of 0.044 (2) Å for the O atom. The dihydropyran ring is in a half-chair conformation and the four essentially planar atoms of this ring form a dihedral angle of 4.6 (2)° with the benzopyran ring system. In the crystal, molecules are linked by weak C—H...O hydrogen bonds, forming chains propagating along [010]. In addition, π–π stacking interactions, with centroid–centroid distances of 3.902 (2) and 3.908 (2) Å, link the hydrogen-bonded chains into layers parallel to (001).