Methoxyacetyl chloride (24.2 mL, 264 mmol) was added dropwise over 10 min to a stirred suspension of the amine (3) (60.0 g, 203 mmol) in a mixture of DCM (300 mL), THF (450 mL) and DIPEA (53.1 mL, 305 mmol) under nitrogen at −5° C. After 10 min the reaction mixture was allowed to warm to RT during which time a dark solution formed. After 30 min a solution of NH3 (7M in MeOH, 30 mL) was added and stirring continued for 1 hr during which time a precipitate formed. The suspension was evaporated in vacuo and the residue was triturated with water (500 mL). The precipitate was collected by filtration, was washed with water (300 mL) and diethyl ether (500 mL) and then dried in vacuo at 60° C. to furnish the title compound (63) as a yellow solid (68 g, 88%): m/z 368 (M+H)+ (ES+).
