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, C(14)H(13)N(3)O(4)S(2)·0.5C(4)H(2)O(4). 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.