Crystal and Molecular Structure of Chelidonine

The crystal and molecular structure of benzophenantridine alkaloid chelidonine, C20H19N05 CM = 353.37) was solved by direct methods and refined by the least-squares technique to a conventional R index of 0.117 for 1888 unique reflections. The crystals are monoclinic, space group P21. Both, B and C rings have half chair conformation and are in cis junction. The N-methyl and C14-hydroxyl groups are in equatorial and axial positions, respectively. The OH-group forms intramolecular hydrogen bond with N atom. Conformation of the molecule is quite different from that found in chelidonine-p-brombenzoateCBB)