To a solution of 5-amino-4-(tert-butoxycarbonylaminomethyl)-1-(2-hydroxyethyl)-1H-pyrazole (243 g) in N,N-dimethylformamide (1.82 L) was added triphenylmethyl chloride (581 g), triethylamine (452 ml) and N,N-dimethylaminopyridine (9.91 g) successively. The reaction mixture was stirred at 70° C. overnight. After cooling to room temperature, the reaction mixture was diluted with ethyl acetate, washed with water (twice) and brine, dried over magnesium sulfate and filtered. The filtrate was evaporated in vacuo. The residue was purified by silica gel column chromatography to give 4-(tert-butoxycarbonylaminomethyl)-5-(tritylamino)-1-[2-(trityloxy)ethyl]-1H-pyrazole, which was crystallized from diisopropyl ether/hexane (1:2). The resulting crystals were collected by filtration on a glass filter, washed with diisopropyl ether/hexane (1:2) and dried in vacuo to give the objective compound (480 g).
