To a solution of 6-oxo-7,8,9,10-tetrahydro-6H-pyrido[3′,2′:4,5]pyrrolo[1,2-a][1,4]diazepine-2-carboxylic acid (Intermediate E, 35 mg, 0.14 mmol) in THF (2 mL) and NMP (0.5 mL) is added 1,1′-carbonyldiimidazole (58 mg, 0.36 mmol). The mixture is stirred at 60° C. for 1 h and is then cooled to room temperature. 5-tert-Butyl-3-aminoisoxazole (80 mg, 0.57 mmol) and DBU (53 μL, 0.36 mmol) are added and the mixture is stirred at 60° C. for 16 h. The mixture is cooled to room temperature and the THF is removed in vacuo. The residue is purified via preparative HPLC using a gradient elution from 10-75% acetonitrile/H2O with 0.1% TFA to afford the title compound (6 mg, 11%). LCMS: 368.20 (M+H+). (System V-med polar)
