Crystal structure of methyl 4-(4-hydroxyphenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate monohydrate

The title hydrate crystallizes with two formula units in the asymmetric unit (Z′ = 2). The organic molecules form a dimer, linked by a pair of N—H⋯O hydrogen bonds. Further hydrogen bonding together with weak C—H⋯π and π–π interactions further consolidates the packing, generating a three-dimensional network.


Chemical context
Dihydropyrimidine (DHPM) derivatives are used in the treatment of disease as antiviral, antitumor, antibacterial and antimalarial agents, as first reported by the Italian chemist Pietro Biginelli in 1893 [Kappe (2000), Nayak et al. (2010) and references therein]. We have been working on the synthesis of various DHPM derivatives for better biological activities (Narayanaswamy et al., 2013;Nayak et al., 2011) and a wide range of applications (Nayak et al., 2009(Nayak et al., , 2010. Here, we report the synthesis and single-crystal structure of the title compound, (I).

Figure 1
The asymmetric unit of the title compound with 50% probability ellipsoids. The double-dashed lines indicate hydrogen bonds.

Figure 2
Crystal structure of title compound showing the dimers formed by N-HÁ Á ÁO hydrogen bonds as well as the links to the water molecules, which donate O-HÁ Á ÁO hydrogen bonds to the ester groups. Table 1 Hydrogen-bond geometry (Å , ).

Figure 3
Three-dimensional crystal structure of the title compound showing the role of the water molecules in the hydrogen-bonding network.
role of the water molecule in the hydrogen-bonding network is shown in Fig. 3.

Synthesis and crystallization
The title compound was obtained by the reaction of three components, viz. methyl acetoacetate, 4-hydroxybenzaldehyde and urea in ethanol solution according to a reported procedure (Tumtin et al., 2010). The reaction progress was monitored by thin layer chromatography and after the completion of the reaction, the solvent was removed and the solid obtained was recrystallized from ethanol to obtain the pure product. Colorless single crystals suitable for X-ray diffraction analysis were obtained by slow evaporation of a solution in ethanol (yield 75%, m.p. 412.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All hydrogen atoms were located in difference Fourier maps and freely refined.

Computing details
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al. (2008); software used to prepare material for publication: SHELXL2014/7 (Sheldrick, 2015). Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.