Solvates of zafirlukast

The crystal structures of three solvates of zafirlukast [systematic name: cyclopentyl N‐{1‐methyl‐3‐[2‐methyl‐4‐(o‐tolylsulfonylaminocarbonyl)benzyl]‐1H‐indol‐5‐yl}carbamate], viz. the monohydrate, C31H33N3O6S·H2O, (I), the methanol solvate, C31H33N3O6S·CH3OH, (II), and the ethanol solvate, C31H33N3O6S·C2H5OH, (III), have been determined by single‐crystal X‐ray diffraction analysis. All three compounds crystallize in the monoclinic crystal system. Zafirlukast adopts a similar Z‐shaped conformation in all three solvates. The methanol and ethanol solvates are isostructural. The packing of the zafirlukast mol­ecules in all three crystal structures is similar and is expressed by hydrogen‐bonded mol­ecules that are related by translation, along (101) in (I) and along the b axis in (II) and (III). The methanol and ethanol solvent mol­ecules are hydrogen bonded to two mol­ecules of zafirlukast. The water mol­ecule, on the other hand, acts as a connector via hydrogen bonds between three mol­ecules of zafirlukast. The solvent mol­ecules are not released at temperatures below the melting points of the solvates.