Trifluoroacetic acid → (1S,9S)-9-(methoxycarbonylamino)-6,10-dioxooctahydro-1H-pyridazino[1,2-a][1,2]diazepine-1-carboxylic acid

To a solution of (1S,9S)-tert-butyl 9-(methoxycarbonylamino)-6,10-dioxooctahydro-1H-pyridazino[1,2-a][1,2]diazepine-1-carboxylate (1.25 g, 3.52 mmol) dissolved into methylene chloride (10 mL) was added trifluoroacetic acid (10 mL). The reaction was stirred at room temperature for 1 h and concentrated in vacuo. Toluene (5 mL) was added and the reaction concentrated in vacuo to afford (1S,9S)-9-(methoxycarbonylamino)-6,10-dioxooctahydro-1H-pyridazino[1,2-a][1,2]diazepine-1-carboxylic acid as a white solid, (587 mg, 68%): ESI-LRMS m/e calcd for C12H17N3O6[M+] 299. found 300 [M+H+].