Hydrazine monohydrate (1.46 ml) was added to a solution of 2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-[1-methyl-5-(tritylamino)-1H-pyrazol-4-yl]acetamide (5.42 g) in ethanol (108 ml) and tetrahydrofuran (54 ml) at room temperature, and the mixture was stirred at 70° C. for 2 hours. The reaction mixture was cooled to 0° C., and the insoluble materials were removed by filtration. The filtrate was concentrated in vacuo. The residue was triturated with diisopropyl ether, collected by filtration and dried in vacuo to give 2-amino-N-[1-methyl-5-(tritylamino)-1H-pyrazol-4-yl]acetamide (3.37 g) as a solid. This product was used in the next step without further purification.
