2.2 g of 2-methoxycarbonylbenzenesulfonamide are added in portions at 0° C. to 2° C. to a mixture of 2.3 g of dicyclohexylcarbodiimide, 120 mg of 4-dimethylaminopyridine and 2.2 g of 4,6-dimethoxypyrimidine-2-carboxylic acid in 80 ml of absolute dichloromethane. The mixture is stirred for 0.5 hour at 0° C. and 2 hours at room temperature, and allowed to stand overnight. The urea which has precipitated is filtered off, the filtrate is concentrated in vacuo, and the residue is stirred for 0.5 hour with 100 ml of 2 N sodium carbonate solution. The aqueous phase is extracted using ether, and a pH of 2-3 is established using concentrated hydrochloric acid. The product which has precipitated is filtered off with suction and dried in vacuo. This gives 1.3 g of N-(4,6-dimethoxypyrimidin-2-yl)carbonyl]-2-methoxycarbonylbenzenesulfonamide of melting point 163°-165° C. (from ethyl acetate).
