To a solution of 1-(1-(4-(4-piperidinyloxy)-2-(2,2,2-trifluoroethoxy)phenylacetyl)piperidin-4-yl)-4H-3,1-benzoxazin-2(1H)-one hydrochloride (0.30 g, 0.5 mmol) from Example 2 in MeOH (7.5 mL) was added sodium acetate (82 mg, 1.0 mmol), acetic acid (0.10 mL, 1.7 mmol), and cyclopropane carboxaldehyde (75 mg, 1.1 mmol). The mixture was stirred at ambient temperature for 30 min and NaBH3CN (61 mg, 1.0 mmol) was added. The solution was stirred for 18 h and the solvent was removed under reduced pressure. The residue was dissolved in EtOAc (50 mL) and washed with saturated aqueous NaHCO3 (3×25 mL). The organic phase was dried (MgSO4), filtered, and the solvent was removed under reduced pressure. The residue was purified by pressurized silica gel column chromatography using 97:3:0.3 CH2Cl2 :MeOH:NH4OH as eluant. The free base was dissolved in MeOH containing 1.5 equivalents of 3 N aqueous HCl. The resulting solution was evaporated under reduced pressure and the residue was lyophilized from CH3CN:H2O to give the hydrochloride salt of the title compound as an amorphous solid.
