6-Hy­droxy-5-[(2-hy­droxy-4,4-dimethyl-6-oxo­cyclo­hex-1-en­yl)(4-nitro­phen­yl)meth­yl]-1,3-di­methyl­pyrimidine-2,4(1H,3H)-dione

In the title compound, C(21)H(23)N(3)O(7), the pyrimidine­dione ring adopts a screw-boat conformation, whereas the cyclo­hexenone ring adopts an envelope conformation, with the C atom bearing the methyl groups as the flap atom. The dihedral angle between the mean planes of the pyrimidine­dione and cyclo­hexenone rings is 58.78 (2)°. The pyrimidine­dione and cyclo­hexenone rings form dihedral angles of 59.94 (3) and 54.73 (2)°, respectively, with the 4-nitro­phenyl ring. Relatively strong intra­molecular O—H⋯O hydrogen bonds are observed. In the crystal, mol­ecules are linked by C—H⋯O hydrogen bonds, forming a chain along the c-axis direction.