To a solution of 40 g of the compound of Example 43 in 320 ml of toluene is added 22 g of acetic anhydride under stirring, and refluxed for 8 hours. After completion of the reaction, the reaction mixture is cooled to 20° C., washed with 300 ml of water twice and dried over anhydrous sodium sulfate. The toluene is concentrated and the residue is recrystallized from ethanol and dried to give 37 g of 1-(2-acetoxyethyl)-3-(3,5-di-tertiary butylphenyl)-1H-pyrazolo[3,4-b]pyridine, melting at 115°-116° C.
