5,6-Dimethyl-pyrazine-2,3-dicarb-oxy-lic acid.

The asymmetric unit of the title compound, C(8)H(8)N(2)O(4), consists of one complete mol-ecule and a second mol-ecule generated by the application of twofold axis. The mean planes of the two carboxyl groups attached to the pyrazine ring at neighboring positions are twisted by 10.8 (1) and 87.9 (1)° in the complete molecule and 43.0 (1)° in the symmetry-generated molecule. The crystal packing features O-H⋯N hydrogen bonds, which link the mol-ecules into layers along [101].