3 NOVEL ISOMERIC PYRANOCOUMARINS FROM CALOPHYLLUM-TEYSMANNII - CALANONE, ISOCALANONE AND TEYSMANONE-A

The crystal and molecular structures of the three title compounds, cal anone -10-phenyl-2H,8H-benzo[1,2-b:3,4-b']dipyran-8-one, (I)], isocala none l-4-phenyl-2H,8H-benzo[1,2-b:3,4-b']dipyran-2-one, (II)] and teys manone A xy-8,8-dimethyl-4-phenyl-2H,8H-benzo[1,2-b:5,4-b'] coumarin, (III)], all having formula C27H20O5 but different isomeric structures, are reported. All of the compounds have the basic coumarin structure. Strong intramolecular hydrogen bonding is present between the carbony l and hydroxyl groups in (1) and (II), but medium strong intermolecula r hydrogen bonding is present in (III). The nature of the hydrogen bon ding determines the planarity of the PhC=O groups. Structures (1) and (II) have a similar PhC=O conformation dictated by intramolecular O-H ... O=C hydrogen bonding, in which the carbonyl groups are twisted awa y from the phenyl ring. The C(E-ortho)-C(E)-C=O torsion angle is 32.8( 2)degrees in (I) and -40.8(2)degrees in (II). In the absence of intram olecular hydrogen bonding, the C=O group is nearly in plane with the b enzene ring in (III) with a C(E-ortho)-C(E)-C=O torsion angle of -2.7 (3)degrees.