Dimethylformamide → HCID 178489261, Verbindung

To a mixture of 3-t-butyl-5-[4-(3-carboxy-5-isoxazolyl)phenyl]-4-(2-methoxyphenyl)-4,5-dihydro-1H-pyrrolo[3,4-c]pyrazol-6-one (0.948 g, 2.0 mmol), triethylamine (0.33 mL, 2.4 mmol) and DMF (15 mL), diphenyl phosphorylazido (0.52 mL, 2.4 mmol) was added, and the mixture was stirred at 60° C. for 2 hr. Then, t-butanol (15 mL) and molecular sieve powder 4A (2 g) was added and the mixture was stirred at 90° C. for 3 hr. Insoluble matter was removed by filtration, water was added and the mixture was extracted with ethyl acetate. The organic layer was washed with aqueous ammonium chloride and brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue was crystallized from dichloromethane to give 3-t-butyl-5-[4-(3-t-butoxy-carbonylamino-5-isoxazolyl)phenyl]-4-(2-methoxyphenyl)-4,5-dihydro-1H-pyrrolo[3,4-c]pyrazol-6-one (0.566 g, 52%) as colorless crystals.