To a solution of 2-((3R,5R,6S)-5-(3-chlorophenyl)-6-(4-chlorophenyl)-3-methyl-2-oxo-1-((S)-1-oxobutan-2-yl)piperidin-3-yl)acetic acid (99 mg, 0.215 mmol; Example 210, Step A) in DCE (3 mL) was added 48.7 mg (0.43 mmol) of 8-oxa-3-azabicyclo[3.2.1]octane (Connolly, T.; Considine, J.; Ding, Z.; Forsatz, B.; Jennings, M.; MacEwan, M.; McCoy, K.; Place, D.; Sharma, A.; Sutherland, K. Organic Process Research & Development. 2010, 14(2), 459-465. Note: reference is for the HCl Salt). Sodium triacetoxyborohydride (91 mg, 0.430 mmol) was added followed by acetic acid (1.2 μL, 0.022 mmol). After stirring overnight, the mixture was partitioned between 5% aq. HCl and ethyl acetate. The organic layer was washed with sat. aq. NaCl solution, dried over Na2SO4, and concentrated. The residue was purified by reversed phase preparatory HPLC (eluent: 0-100% MeCN +0.1% TFA in water +0.1% TFA, over 20 minutes). Fractions containing the product were transferred to a separatory funnel and sat. aq. NaHCO3 and dichloromethane were added. The aqueous layer was back extracted with dichloromethane. The combined organic layers were washed with sat. aq. NaCl solution, dried over anhydrous Na2SO4, filtered and the filtrate was concentrated to afford the title compound.
