Crystal structure of a 2:1 co-crystal of meloxicam with acetylendicarboxylic acid

The pharmaceutical 2:1 co-crystal of meloxicam [MXM; systematic name: 4-hydroxy-2-methyl-N-(5-methylthiazol-2-yl)-2H-1,2-benzothiazine-3-carboxamide 1,1-dioxide] with acetylenedicarboxylic acid (ACA; systematic name: but-2-ynedioic acid), crystallizes with one MXM molecule and half an ACA molecule in the asymmetric unit, C14H13N3O4S2·0.5C4H2O4. The mid-point of the triple bond of ACA is located on an inversion centre. In the crystal, the two stereoisomers of MXM with respect to the N atom of the sulfonamide group are related by the inversion centre. The carbonyl and hydroxy groups belonging to the MXM molecule are involved in an intramolecular O—H...O hydrogen bond. The structure-forming motif includes two MXM molecules linked via an ACA conformer through N—H...O and O—H...N hydrogen bonds, similar to MXM co-crystals with other dicarboxylic acids