To a stirred solution of aniline 27 (634 mg, 1.249 mmol) and pyridine (303 μL, 3.746 mmol) in DMF (15 mL) at 0° C. under nitrogen was added dropwise phenyl chloroformate (415 μL, 3.308 mmol). The reaction mixture was stirred at 0° C. for 2 hrs and cyclopropylamine (433 μL, 6.250 mmol) was slowly added. The reaction mixture was allowed to warm-up to RT over 30 min and was heated at 55° C. for 5 hr then cooled to RT. The reaction mixture was partitioned between AcOEt and a saturated aqueous solution of sodium bicarbonate. The organic layer was successively washed with a saturated aqueous solution of sodium bicarbonate, 1N NaOH, a saturated aqueous solution of ammonium chloride and brine, dried over anhydrous magnesium sulfate, filtered and concentrated. The residue was purified by Biotage (SiliaFlash 40 g cartridge; MeOH/DCM: 0/100 to 10/90 over 20 CV). The desired fractions were collected, concentrated and dried under high vacuum to afford the title compound 28 (754 mg, 1.27 mmol, quant. yield) as a pale yellow sticky oil. MS (m/z): 591.6 (M+H).
