1,3,5,7,9,11,13,15-Octaazapentacyclo[9.5.1.13,9.06,18.014,17]octadecane-4,8,12,16-tetrone monohydrate: a methylene-bridged glycoluril dimer

In the title compound, C10H12N8O4·H2O, prepared from the reaction of glycoluril with paraformaldehyde, the organic molecule has mm symmetry. The asymmetric unit comprises one quarter of the molecule and a half-molecule of water. The dimer is formed by bridging two glycoluril molecules with methylene groups at the 1 and 6 positions. In the crystal structure, molecules are linked via N—H...O and O—H...O hydrogen bonds, forming a two-dimensional framework.