A mixture of 4-(2,2-dimethylpropionyl)-3-hydroxy-5-(2-methoxycarbonylmethyloxyphenyl)-1-(4-thiophene-3-ylphenyl)-1,5-dihydropyrrole-2-one (0.207 g, 0.41 mmol), hydrazine hydrate (0.022 mL, 0.45 mmol) and acetic acid (3.1 mL) was stirred at 95° C. for 1 hour. After the reaction was completed, saturated sodium bicarbonate solution was poured into the reaction mixture, and the mixture was extracted with chloroform. The extract was washed with brine, dried over anhydrous sodium sulphate, and then concentrated in vacuo. The resulting residue was triturated with ethyl ether and diisopropyl ether to give 3-t-butyl-5-(4-thiophene-3-ylphenyl)-4-(2-methoxycarbonylmethyloxyphenyl)-4,5-dihydro-1H-pyrrolo[3,4-c]pyrazole-6-one (0.191 g, yield: 93%) as pale brown solid.
