Methyl 2-amino-4,5-dimethoxybenzoate

The title compound, C10H13NO4, is essentially planar, with an r.m.s. deviation of 0.049 Å. An intramolecular C—H⋯O hydrogen bond occurs and the amino group forms an intramolecular N—H⋯Oester hydrogen bond; the other H atom forms an intermolecular N—H⋯Ocarbonyl hydrogen bond, leading to the formation of a helical chain that runs along the b-axis direction.

The title compound, C 10 H 13 NO 4 , is essentially planar, with an r.m.s. deviation of 0.049 Å . An intramolecular C-HÁ Á ÁO hydrogen bond occurs and the amino group forms an intramolecular N-HÁ Á ÁO ester hydrogen bond; the other H atom forms an intermolecular N-HÁ Á ÁO carbonyl hydrogen bond, leading to the formation of a helical chain that runs along the b-axis direction.
The University of the Witwatersrand and the Molecular Sciences Institute are thanked for providing the infrastructure and financial support. Special thanks go to Dr Andreas Lemmerer of the University of the Witwatersrand for his contributions and insights toward this project. TNH wishes to thank the University of the Witwatersrand research committee for a postdoctoral fellowship.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NG5347).

Comment
The molecular structure of (I) is presented in Figure 1, and was obtained by recrystallization of the commercially available compound. The title compound consists of an amino (C2) and methoxy (C4 and C5) substituted benzoate which was found to be essentially planar with an r.m.s. deviation of 0.049 Å; the dihedral angles shown in Table 1 further reinforce the planarity of (I). The maximum deviation observed below the calculated mean plane was found for the carbonyl oxygen (O1) at -0.136 (1) Å. Two intramolecular hydrogen bonds found between the phenyl carbon (C6), the amino (N1) and the ester O atoms (O1 and O2) with distances of 2.713 (1) Å and 2.702 (2) Å, effectively lock the ester into the molecular plane. The last hydrogen bond interaction observed between the amino (N1) and an adjacent carbonyl oxygen (O1) (symmetry operator [-x, y + 1/2, -z -1/2]) with a distance of 2.947 (1) Å results in a helical chain along [0 1 0] (Figure 2).

Experimental
Methyl 2-amino-4,5-dimethoxybenzoate was obtained commercially. (I) was redissolved in warm MeOH and allowed to cool to room terperature. Yellow crystals suitable for single-crystal diffraction were obtained by slow evaporation over a few days.

Refinement
All hydrogen atoms were positioned geometrically and refined using a riding model, with C-H = 0.95 Å U iso (H)= 1.2 U eq (C) for the aromatic H and with C-H = 0.98 Å U iso (H)= 1.5 U eq (C)for methyl H atoms. The methyl groups were allowed to rotate with a fixed angle arround the C-C bond to best fit the experimental electron density. The amino hydrogens were freely refined.