To a solution of the title compound from Example 5 Step C (194 mg, 0.34 mmol) in DCM (2 mL) were added diisopropyl ethyl amine (0.60 mL, 3.41 mmol) and methyl chloroformate (0.08 mL, 1.02 mmol). The reaction mixture was stirred for 1 h at ambient temperature, then was diluted with sat. aq. NaHCO3 and extracted with DCM. The organic phase was separated, dried over sodium sulfate, filtered, and concentrated in vacuo. The product was used in the subsequent step without further purification: LCMS m/z 626.9 [M+H]+.
