4-[(4-Acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid

In the title compound, C13H13NO4, the N—C(=O) bond length of 1.354 (2) Å is indicative of amide-type resonance. The dihedral angle between the mean planes of the benzene ring and oxoamine group is 36.4 (3)°, while the mean plane of the 2-methylidene group is inclined by 84.2 (01)° from that of the oxoamine group. In the crystal, classical O—H⋯O hydrogen bonds formed by the carboxylic acid groups and weak N—H⋯O weak interactions formed by the amide groups and supported by weak C—H⋯O interactions between the 2-methylidene, phenyl and acetyl groups with the carboxylic acid, oxoamine and acetyl O atoms, together link the molecules into dimeric chains along [010]. The O—H⋯O hydrogen bonds form R 2 2(8) graph-set motifs.

BN thanks the UGC for financial assistance through a BSR one-time grant for the purchase of chemicals. PSN thanks Mangalore University for research facilities and DST-PURSE financial assistance. JPJ acknowledges the NSF-MRI program (grant No. CHE-1039027) for funds to purchase the X-ray diffractometer.
Supporting information for this paper is available from the IUCr electronic archives (Reference: ZL2589).

Comment
Amide bonds play a major role in the elaboration and composition of biological systems, which are the main chemical bonds that link amino acid building blocks together to give proteins. Amide bonds are not limited to biological systems and are indeed present in a huge array of molecules, including major marketed drugs. Amide derivatives possessing antiinflammatory (Galanakis et al., 2004;Kumar et al., 1993;Ban et al., 1998), antimicrobial (Ukrainets et al., 2006), antitubercular (Lesyk et al., 2004) and antiproliferative (Gududuru et al., 2004) activities are reported in the literature.
In the title compound, The C=C bond is present as its anti-Saytzeff tautomer. The N-C(=O) bond length of 1.354 (2)A (A) is indicative of amide-type resonance (Fig. 1). All other bond lengths are in normal ranges (Allen et al., 1987). In the crystal, classical O-H···O hydrogen bonds formed by the carboxylic groups and N-H···O weak intermolecular interactions formed by the amide groups and supported additionally by weak C-H···O intermolecular interactions between the 2-methylidene, phenyl and acetyl groups with the carboxylic, oxoamine and acetyl oxygen atoms (Table 1), together link the molecules into dimeric chains along [0 1 0] (Fig. 2). The O-H···O hydrogen bonds form R 2 2 (8) graphset motifs. The dihedral angle between the mean planes of the phenyl ring (C6-C10) and oxoamine group (C1/C2/O1/N1) is 36.4 (3)°, while the mean plane of the 2-methylidene group (C2-C5) is further inclined by 84.2 (1)° from that of the oxoamine group.

Refinement
The OH atom was located by a difference map and refined isotropocally. All of the remaining H atoms were placed in their calculated positions and then refined using the riding model with Atom-H lengths of 0.95Å (CH), 0.98 -1.00Å (CH 2 ), 0.98Å (CH 3 ) or 0.88Å (NH). Isotropic displacement parameters for these atoms were set to 1.2 (CH, CH 2 , NH) or 1.5 (CH 3 ) times U eq of the parent atom. Idealised Me was refined as a rotating group.  ORTEP drawing of C 13 H 13 NO 4 , showing the labeling scheme with 30% probability displacement ellipsoids.  Synthesis of C 13 H 13 NO 4 . 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. 0.0427 (10) 0.0312 (9) 0.0281 (9) 0.0000 (7) −0.0097 (7) 0.0027 (7) Geometric parameters (Å, º)