rac-N-Benzylisatincreatinine (unknown solvate)

The title compound, C19H18N4O3 [systematic name: (RS)-1-benzyl-3-hydroxy-3-(2-imino-3-methyl-5-oxoimidazolidin-4-yl)-2,3-dihydro-1H-indol-2-one], was prepared as a racemate (RR and SS) by the aldol condensation of N-benzylisatin with creatinine in the presence of sodium acetate in acetic acid. The r.m.s. deviation of the isatin ring system is 0.033 Å. The benzyl group is disordered over two orientations, with refined occupancies of 0.847 (7) and 0.153 (7). The dihedral angles between the isatin ring system and the benzene ring (major disorder component) and the imidazole ring are 82.82 (7) and 51.31 (3)°, respectively, In the crystal, molecules are linked into (001) sheets by N—H⋯O and O—H⋯N hydrogen bonds, which incorporate R 2 2(9) ring motifs. The crystal was grown from mixed solvents (ethanol, methanol and possibly also ethyl acetate). These solvents are disordered in the crystal and the resulting electron density was found to be uninterpretable. The solvent contribution to the scattering was removed with the SQUEEZE routine in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155]. The formula mass and density do not take account of the solvent.

The title compound, C 19 H 18 N 4 O 3 [systematic name: (RS)-1benzyl-3-hydroxy-3-(2-imino-3-methyl-5-oxoimidazolidin-4yl)-2,3-dihydro-1H-indol-2-one], was prepared as a racemate (RR and SS) by the aldol condensation of N-benzylisatin with creatinine in the presence of sodium acetate in acetic acid. The r.m.s. deviation of the isatin ring system is 0.033 Å . The benzyl group is disordered over two orientations, with refined occupancies of 0.847 (7) and 0.153 (7). The dihedral angles between the isatin ring system and the benzene ring (major disorder component) and the imidazole ring are 82.82 (7) and 51.31 (3) , respectively, In the crystal, molecules are linked into (001) sheets by N-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds, which incorporate R 2 2 (9) ring motifs. The crystal was grown from mixed solvents (ethanol, methanol and possibly also ethyl acetate). These solvents are disordered in the crystal and the resulting electron density was found to be uninterpretable. The solvent contribution to the scattering was removed with the SQUEEZE routine in PLATON [Spek (2009). Acta Cryst. D65,[148][149][150][151][152][153][154][155]. The formula mass and density do not take account of the solvent.   Table 1 Hydrogen-bond geometry (Å , ).   (Penthala et al., 2010a). The title compound was prepared by the aldol condensation of N-benzylindol-2,3-dione (N-benzylisatin) with 2-amino-1-methyl-1H-imidazol-4(5H)-one (creatinine) in the presence of sodium acetate in acetic acid. Earlier, we reported on the crystal structure of isatin creatinine analogs containing N-methyl and Nphenyl substituents (Penthala et al., 2009a,b). To obtain detailed information on the structural conformations of the molecules for analysis of structure-activity relationships (SAR), we determined the X-ray crystal structure of the title compound ( Fig. 1). In the crystal, the benzyl group is disordered over two positions, with refined occupancies of 0.847 (7) and 0.153 (7). The isatin ring is almost planar, with r.m.s deviations from the mean plane = 0.0508 (11) Å, and with bond distances and angles comparable to those reported for other isatin derivatives (Tang et al., 2009). The benzene ring of the benzyl group makes a dihedral angle with the mean plane of the isatin ring of 82.82 (7)°. The title compound was isolated as a racemate (RR and SS). In the crystal, the molecules are linked into 2-D pleated-sheet networks in the ab plane by a series of intermolecular N-H-O and O-H-N hydrogen bonds. Within these sheets, the hydrogen bonds O9-H···N12, N13-H13A···O11 and N13-H13B···O1 create R 2 2 (9) ring motifs.

Experimental
The title compound was prepared according to a previously reported procedure (Penthala et al., 2009a,b).
Recrystallization from ethanol afforded the title compound as pale yellow plates. Spectroscopic data for rac-N-benzyl-

Figure 1
A view of (I). Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonding in the crystal structure of (I). Dashed lines represent hydrogen bonds. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.28 e Å −3 Δρ min = −0.30 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.00043 (9) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (