A solution of NH4Cl (1.4 mL, 40 mmol) and Et3N (5.6 mL, 40 mmol) in DMF (6 mL) was added to a solution of 1-tert-butoxycarbonylspiro[piperidine-4,4′-pyrrolo[2,1-c][1,4]benzoxazine]-7′-carboxylic acid (3.1 g, 8.0 mmol), HATU (3.3 g, 8.8 mmol), and Et3N (2.5 mL, 18 mmol) in DMF (6 mL). The mixture was stirred at room temperature for 1 h. The reaction mixture was diluted with ethyl acetate and was washed with saturated sodium bicarbonate solution. The organics were dried over sodium sulfate, filtered and evaporated. Purification of the residue by silica gel chromatography eluting with 0-100% EtOAc in Hexanes gave tert-butyl 7′-carbamoylspiro[piperidine-4,4′-pyrrolo[2,1-c][1,4]benzoxazine]-1-carboxylate (2.7 g, 89%). ESI-MS m/z calc. 383.4, found 384.7 (M+1)+. Retention time: 1.60 minutes (3 min run).
