(4-Acetylamino-3-benzyloxy-phenyl)-carbamic acid 9H-fluoren-9-ylmethyl ester (420) (3 g, 6.28 mmol) was dissolved in a mixture of MeOH (15 mL) and NMP (10 mL). 4.0 M HCl in dioxane (20 mL) was added and the mixture was refluxed for 40 h. LC-MS indicated complete de-protection at this point. The mixture was diluted with EtOAc (200 mL), washed with saturated aqueous NaHCO3 (3×300 mL), water (100 mL) and brine (100 mL) via extraction, dried over MgSO4 and upon concentration under reduced pressure, a precipitate formed. Collection by filtration under reduced pressure followed by drying under high vacuum for 16 h gave the desired product (65) as a beige/pink powder (1.28 g, 2.93 mmol, 46.7% yield). LC-MS (ESI): (exact mass: 436.18) m/e=437.2 [M+1]+ (100%), 873.5 [2M+1]+ (100%).
