THE STRUCTURE OF A COUMARIN DERIVATIVE RELATED TO THE CARCINOGEN BENZ[A]ANTHRACENE

The three-dimensional structure of 3-methyl-2H-anthra-[1,2-b]pyran-2-o ne, an anticarcinogenic coumarin related to the carcinogen benz[a]anth racene, has been determined by X-ray diffraction techniques, The molec ule, apart from hydrogen atoms in the methyl group, is flat, the maxim um deviation from its least squares best plane being 0.13 Angstrom. Th e carbonyl C=O bond length is normal [1.206(1)Angstrom] and the bondin g throughout the molecule indicates localization of double bonds withi n the coumarin ring, but some delocalization of electrons in the other rings, Molecules pack in planes parallel to each other, the coumarin ring oxygen atom lying between two aromatic rings of other coumarin mo lecules, The bulky methyl groups are not involved in such stacking, wh ile the carbonyl groups attract C-H groups in neighboring molecules by way of C-H ... O interactions; These are the types of interactions th at such coumarins could make if they bound to hydrophobic areas in bio logical macromolecules.