[CH:1]([NH:4][C:5]1[CH:10]=[CH:9][N:8]=[CH:7][C:6]=1[S:11]([NH2:14])(=[O:13])=[O:12])([CH3:3])[CH3:2].[CH2:15]=O.Cl>C(O)(C)C.C(OCC)(=O)C>[CH:1]([N:4]1[C:5]2[CH:10]=[CH:9][N:8]=[CH:7][C:6]=2[S:11](=[O:13])(=[O:12])[NH:14][CH2:15]1)([CH3:3])[CH3:2]A mixture of 1 g of 4-isopropylaminopyridine-3- sulfonamide (Preparation 3) and 1 g of paraformaldehyde in 20 cm3 of isopropanol to which 10 drops of ethyl acetate saturated with gaseous HCl have been added is brought to reflux for 3 hours. After cooling, the crystalline precipitate is filtered and washed with isopropanol. The precipitate is dissolved in 150 cm3 of hot methanol. The possible insoluble material is filtered. The filtrate is concentrated to dryness and the residue is taken up in 30 cm3 of water. The aqueous suspension is adjusted to a pH of 7-7.5 (NaHCO3) and the precipitate corresponding to the title compound is filtered, washed with water and dried.
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