A solution of 1 g of p-toluenesulphonyl chloride in 10 cm3 of diethyl ether is added, at a temperature in the region of 20° C., to a solution of 1 g of 6,6-diphenyl-6,7-dihydro-1H-indazol-3-carboxylic acid in 10 cm3 of water and 10 cm3 of a normal aqueous sodium hydroxide solution. The reaction mixture, which sets to a solid after about ten minutes of vigorous stirring, is diluted with 10 cm3 of water. After stirring for about eighteen hours at a temperature in the region of 20° C., the reaction mixture is filtered. The solid is washed with three times 20 cm3 of water and then suspended in 20 cm3 of water. 10 cm3 of a normal aqueous hydrochloric acid solution are added. The mixture is extracted with three times 50 cm3 of ethyl acetate. The combined organic phases are successively washed with three times 70 cm3 of water and once 70 cm3 of saturated aqueous sodium chloride solution and then dried over magnesium sulphate, filtered and concentrated under reduced pressure (13 kPa). The residue is purified by flash chromatography on a column of silica [eluent: dichloromethane/methanol (95/5 by volume)]. 0.94 g of 6,6-diphenyl-1-(4-toluenesulphonyl)-6,7-dihydro-1H-indazol-3-carboxylic acid is thus obtained in the form of a solid, the characteristics of which are as follows:
