organic compounds
The title compounds, C7H10N4O5 (I) and C6H8N4O5 (II), each consist of a five-membered ring fused to a smaller ring. In compound (I), the C-C bridging bond distance [1.571 (4) Å] is longer than the expected distance of 1.54 Å for a C-C bond in a cyclobutane ring. In compound (II), however, the corresponding C-C bridging bond distance [1.507 (5) Å] is consistent with the expected bond length (1.51 Å) in a cyclopropane ring. The increase in the C-C bridge distance in compound (I) is most likely due to steric effects resulting from the additional methyl substituents.