To 2 g (0.016 mol) of sodium sulfite and 2.4 g (0.029 mol) of sodium hydrogen carbonate were added 100 ml of water and 20 ml of acetonitrile and the mixture was stirred at 30° C. To the mixture was added dropwise a solution of 10.5 g (0.013 mol) of 3,5-di-(2,4-di-tert-amylphenoxypropylcarbamoyl)benzenesulfonyl chloride obtained in the aforesaid step dissolved in 100 ml of acetonitrile. After stirring the resultant mixture for one hour, the reaction mixture was poured onto ice water and extracted with 150 ml of ethyl acetate. The ethyl acetate layer was washed thrice with cold water and dried over Glauber's salt. After filtrating away the Glauber's salt, the residue was concentrated to dryness to provide 8.6 g (yield of 82.8%) of a solid product.
