Methyl 2,4-dihydroxy-5-(2-methylpropanamido)benzoate

In the title compound, C12H15NO5, the dihedral angle between the benzene ring and the C atoms of the terminal isopropyl group is 83.48 (16)°. Intramolecular N—H⋯O and O—H⋯O hydrogen bonds generate S(5) and S(6) rings, respectively. In the crystal, molecules are linked by O—H⋯O hydrogen bonds, generating C(7) chains propagating in [001]. Weak aromatic π–π stacking [centroid–centroid separation = 3.604 (3) Å] is also observed.


Comment
The title compound (I, Fig. 1) has been prepared for derivatization and for the biological studies in continuation to form different derivatives of methyl 5-amino-2,4-dihydroxybenzoate (Naz et al., 2013). The crystal structure of 3-hydroxy-2-(isobutyrylamino)benzamide (Chen et al., 2011) has been published which is related to the title compound.
In (I), the groups A (C1-C8/O1-O4/N1) of methyl 5-amino-2,4-dihydroxybenzoate is almost planar with r. m. s.  5) and S(6) ring motifs. There also exist strong intermolecular H-bondings of O-H···O type due to which C(7) chains are formed (Table 1, Fig. 2) resulting in the formation of one dimensional polymeric network along the c-axis. There also exist π-π interactions between the centroids of benzene rings at a distance of 3.604 (3) Å.

Experimental
Equivalent amounts of methyl 5-amino-2,4-dihydroxybenzoate (0.2 g, 1.1 mmol) and Isobutyric anhydride (0.2 ml, 1.1 mmol) were heated at 333 K for 3 h in dimethylformamide (DMF). The reaction mixture was kept for 48 h to afford brown needles of the title compound.

Refinement
The  View of the title compound with displacement ellipsoids drawn at the 50% probability level.

Figure 2
The partial packing of (I), which shows that molecules form S ( where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.25 e Å −3 Δρ min = −0.19 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0032 (7) Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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 > σ(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.