To Boc-anhydride (138 mg, 0.631 mmol) in dichloromethane (1 mL) was added DMAP (55.1 mg, 0.451 mmol) followed by a solution of 4-{[3-(methyloxy)phenyl]oxy}aniline (97 mg, 0.451 mmol) in dichloromethane (1 mL). The mixture was stirred for 10 min. The brown solution thus obtained was added to Solution 1 via syringe with shaking at 35° C. and shaking was continued at this temperature for 2 hours. The solution was then kept at room temperature for ca. 64 hours. Conc. aq. HCl (ca. 0.8 mL) was added and the heterogenous mixture was heated at 100° C. for 2 hours with shaking, allowing the DCM to distill off through a glass capillary. After cooling to room temperature, the residue was diluted with water (ca. 3 mL) and extracted with dichloromethane (2 times ca. 2 mL). The dichloromethane extracts were concentrated under vacuum. The residue was purified by silica gel chromatography (Biotage system, 10 g column) eluting with a gradient cHex/EtOAc from 95/5 to 0/100 to give a brown viscous oil that was dissolved in Et2O (ca. 0.7 mL) and cHex (ca. 0.1 mL) and kept over night. The overstanding faint brown solution was decanted from a small quantity of a brown oil that had separated out. As the solvent was allowed to evaporate from this solution crystallisation initiated. The material thus obtained was allowed to dry and then triturated with Et2O (2 times ca. 0.5 mL) to afford, after drying, the title compound as a solid (28 mg).
