In a dry 25-mL RBF, phosgene (0.25 ml, 0.47 mmol) was dissolved in DCM (2 mL) and the solution was cooled to 0° C. A solution of benzyl morpholine-2-carboxylate (50%, 0.070 g, 0.16 mmol, Example 458, Step 2) and N-ethyl-N-isopropylpropan-2-amine (0.041 ml, 0.24 mmol) in DCM (2 mL) was added. The solution was stirred at 0° C. for 4 h, and the ice bath was removed, and the mixture stirred at RT for 1 hour. The reaction mixture was concentrated, and the residue dissolved in DCM (2 mL), and N-ethyl-N-isopropylpropan-2-amine (0.041 ml, 0.24 mmol) and 3,3-dimethylpiperidine (0.022 g, 0.20 mmol) were added by syringe. After 14 h, the reaction mixture was concentrated. The residue was purified through silica gel (20 mL) using 50% EtOAc-hexane to afford the title compound. MS m/z 361 (M+1).
