To a solution of 5-fluoro-N-(2-(isopropylamino)-2-oxoethyl)-2-nitrobenzamide (1.0 g, 3.53 mmol) (Intermediate 2A) in acetonitrile (20 mL) was added potassium carbonate (1.46 g, 10.9 mmol) followed by (1S,4S)-tert-butyl 2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (0.70 g, 3.53 mmol). The resulting suspension was heated to reflux at 90° C. for 6 hours. The reaction mixture was allowed to cool to room temperature, then filtered and concentrated. The resultant crude material was purified by a 25 g silica column in neat ethylacetate (Biotage Snap cartridge). Fractions of the product were combined and reduced to dryness under reduced pressure to afford (1S,4S)-tert-butyl 5-(3-(2-(isopropylamino)-2-oxoethylcarbamoyl)-4-nitrophenyl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (1.5 g, 3.25 mmol).
