Hydrogen-bonding patterns in 5-fluorocytosine–melamine co-crystal (4/1)
The asymmetric unit of the title compound comprises two independent 5-fluorocytosine molecules and one half-molecule of melamine. The 5-fluorocytosine molecules are linked through two different homosynthons; one is formed via a pair of N—H⋯O hydrogen bonds and the second via a pair of N—H⋯N hydrogen bonds. The 5-fluorocytosine and melamine molecules interact via N—H⋯O, N—H⋯N and N—H⋯O, N—H⋯N, C—H⋯F hydrogen bonds.
Protonation of inorganic 5-Fluorocytosine salts
Abstract 5-Fluorocytosine (5-FC) has been widely used for the treatment of fungal infections and recently was found to exert an extraordinary antineoplastic activity in gene directed prodrug therapy. However, despite of its intense use, 5-FC exhibits tabletability issues due its physical instability in humid environments, leading to transition from the anhydrous to monohydrate phase. By considering that salt formation is an interesting strategy to overcome this problem, in this paper crystal engineering approach was applied to the supramolecular synthesis of new 5-FC salts with sulfuric, hydrobromic and methanesulfonic inorganic acids. A total of four structures were obtained, namely 5-FC sulfate monohydrate (1:1:1), 5-FC hydrogen sulfate (1:1), 5-FC mesylate (1:1) and 5-FC hydrobromide (1:1), the last one being a polymorphic form of a structure already reported in the literature. These novel salts were structurally characterized by single crystal X-ray diffraction and its supramolecular organization were analyses by Hirshfeld surface analysis. The vibrational behavior was evaluated by Raman spectroscopy and it was found to be consistent with the crystal structures.
The crystal structure of 3-methyluracil from X-ray powder diffraction data
Abstract The crystal structure of 3-methyluracil has been determined ab initio by conventional monochromatic X-ray powder diffraction data. The crystal data are: orthorombic, a =6.6294(1), b =13.1816(3), c =6.53938(9) (A), V =571.45(3) (A 3 ), space group Pbnm , Z =8. The structure was solved by direct methods and the final Rietveld refinement converged to R p =0.0398, R wp =0.0528, R Bragg =0.0294. The crystal structure exhibits endless chains of planar molecules, connected via head-to-tail N–H⋯O hydrogen bonds.