Crystal structure of di-bromo-meth-oxy-seselin (DBMS), a photobiologically active pyran-ocoumarin.

The title compound, CHBrO [systematic name: -(9,10)-3,9-dibromo-10-methoxy-8,8-dimethyl-9,10-dihydropyrano[2,3-]chromen-2(8)-one], is a pyran-ocoumarin derivative formed by the bromination of seselin, which is a naturally occurring angular pyran-ocoumarin isolated from the Indian herb . In the mol-ecule, the benzo-pyran ring system is essentially planar, with a maximum deviation of 0.044 (2) Å for the O atom. The di-hydro-pyran 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 benzo-pyran ring system. In the crystal, mol-ecules are linked by weak C-H⋯O hydrogen bonds, forming chains propagating along [010]. In addition, π-π stacking inter-actions, with centroid-centroid distances of 3.902 (2) and 3.908 (2) Å, link the hydrogen-bonded chains into layers parallel to (001).