[CH3:1][O:2][C:3]([C:5]1[S:6][CH:7]=[CH:8][C:9]=1[S:10](Cl)(=[O:12])=[O:11])=[O:4].[CH2:14]([O:16][C:17](=[O:21])[CH2:18][NH:19][CH3:20])[CH3:15].O.Cl>C(Cl)(Cl)Cl>[CH3:1][O:2][C:3]([C:5]1[S:6][CH:7]=[CH:8][C:9]=1[S:10](=[O:12])(=[O:11])[N:19]([CH2:18][C:17]([O:16][CH2:14][CH3:15])=[O:21])[CH3:20])=[O:4]
20 G. of 3-chlorosulfonylthiophene-2-carboxylic acid methyl ester are dissolved in absolute chloroform, whereupon 21 g. of sarcosine ethyl ester are added dropwise during 10 minutes. In so doing, the mixture warms up to 50° C. After 20 minutes, the mixture is cooled, shaken once each time with water, 0.5 -N hydrochloric acid and a sodium bicarbonate solution, dried and evaporated. The remaining oil is brought to crystallization with ethanol. There is obtained 3-(N-carbethoxymethyl-N-methyl-sulfamoyl)-thiophene-2-carboxylic acid methyl ester of melting point 84°-85° C.
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