(2S,3R,4S,4aR)-2,3,4,7-Tetrahydroxy-3,4,4a,5-tetrahydro[1,3]dioxolo[4,5-j]phenanthridin-6(2H)-one hemihydrate

The title natural compound, isolated from Narcissus pseudonarcissus var. King Alfred crystallizes as a hemihydrate, C14H13NO7·0.5H2O, with four crystallographically independent dioxolophenanthridinone molecules and two crystallographically independent solvent water molecules in the asymmetric unit. All four crystallographically independent dioxolophenanthridinone molecules are geometrically very similar and differ only in the orientations of the three hydroxy groups at the terminal cyclohexene rings. The five-membered dioxolane ring has a planar conformation (the r.m.s. deviations are 0.010, 0.019, 0.025 and 0.004 Å, for the four crystallographically independent molecules), and the six-membered dihydropyridone and cyclohexene rings adopt sofa conformations in each molecule. The flattened structure of each dioxolophenanthridinone molecule is supported by a strong intramolecular O—H...O hydrogen bond. The N atom has a slightly pyramidalized configuration. In the crystal, the dioxolophenanthridinone molecules form layers parallel to (101) with O—H...O and N—H...O hydrogen bonds linking the dioxolophenanthridinone molecules both within and between the layers and the water molecules, forming a three-dimensional framework. The absolute configurations of the chiral centers are 2S, 3R, 4S and 4aR