10-Hydroxy-9-methoxy-5,6,13,13a-tetrahydro[1,3]dioxolo[4,5-g]isoquino[3, 2-a]-isoquinolin-8-one

In the title compound, 8-oxotetrahydrothalifendine, C₁₉H ₁₇NO₅, the dihydropyrido and pyrido moieties adopt the intermediate conformations of envelope-screw-boat and envelope-twist, respectively. The dihedral angle between the two benzene rings is 37.16 (8)°. In the crystal structure, the molecules translated by a unit along the c axis are linked by three weak C-H⋯O intermolecular interactions to form a molecular chain. Along the a axis, the adjacent chains related by screw symmetry are connected by a strong O-H⋯O and a weak C-H⋯O intermolecular interaction to form layers parallel to the bc plane.