organic compounds
The structure of the title compound (systematic name: 2-{2-[1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indol-3-yl]acetoxy}acetic acid monohydrate, C21H18ClNO6·H2O) contains one-dimensional infinite hydrogen-bonded chains. Molecules of acemetacin, a nonsteroidal anti-inflammatory drug, and water are linked by three independent O—HO bonds. The central unit in each chain consists of a sequence of alternating centrosymmetric R44(12) and R44(18) rings, which are edge-fused. Each ring links two acemetacin and two water molecules. A comparison with seven related structures reveals that molecules of acemetacin, indomethacin and their analogues can adopt two principal conformations.