To a solution of (1R,3S)-3-[(3R)-tetrahydrofuran-3-yl]-3-(4-[4-(trifluoromethyl)pyridin-2-yl]piperazin-1-ylcarbonyl)cyclopentanamine dihydrochloride (73.8 mg, 0.152 mmol), 3-methoxytetrahydro-4H-pyran-4-one (59.4 mg, 0.456 mmol) and triethylamine (0.0848 mL, 0.608 mmol) in dry methylene chloride (4.1 mL) was added sodium triacetoxyborohydride (96.7 mg, 0.456 mmol). After being stirred at room temperature under N2, the reaction was quenched with aqueous NaHCO3 and diluted with CH2Cl2. The organic layer was separated and the aqueous layer was extracted with CH2Cl2 three times. The organics were combined, dried over MgSO4, filtered, concentrated and purified by silica gel chromatography (Combi-Flash system, 0 to 40% MeOH in EtOAc, gradient, 12 gram column) to provide the desired product (20 mg, 41%). MS calculated for C26H37F3N4O4: (M+H) 527.3; found 527.3.
