Boldine (5,6,6a,7-tetrahydro- 1,10-dimethoxy-6-methyl-
4H-dibenzo[de,g]quinoline-2,9-diol) is an aporphine
alkaloid noted for its antioxidant properties. A salient
feature of the molecule is the non-planarity of the
biphenyl system, which exhibits a dihedral angle of
151.1 (8) ° between the least-squares planes of the
two benzenoid rings and torsion angles of 25.7 (3),
- 150.6 (2), - 155.9 (2) and 27.8 (3) ° about the biphenyl
bond. Methoxy C atom C 13 lies only 0.195 (4) A above
the mean plane of the ring to which it is attached, with
torsion angles about the C10--O2 bond of 168.6 (2)
and -11.344) °. Methoxy C atom C14 is displaced
-1.101 (3)A from the corresponding ring plane, with
torsion angles about the C1---O3 bond of 102.3 (2) and
-79.7 (3) °. All intramolecular bonds and angles are
within the expected range.