The crystal structure of the monohydrate form of spirapril hydrochlori
de, pyl)-1,4-dithia-7-azaspiro[4.4]nonane-8-carboxylic acid hydrochlor
ide, C22H31N2O5S2+.Cl-.H2O, was determined. The spirapril molecules ad
opt a trans conformation along the amide bond. The incorporated water
molecules form hydrogen bonds with the host molecules.