Trifluoroacetic acid → Ammonia

A solution of tert-butyl (3R)-6-cyclohexyl-3-(3-{[4-(dimethylamino)-1-piperidinyl]carbonyl}-1,2,4-oxadiazol-5-yl)hexanoate (Preparation 25) (652 mg, 1.37 mmol) in dichloromethane (15 ml) was cooled to 0° C. and treated with trifluoroacetic acid (5 ml). The resulting mixture was stirred for 2 hours being allowed to warm to room temperature over this time. The solvent was removed under reduced pressure and the residue azeotroped from toluene. The residue was purified by column chromatography on silica gel eluting with a gradient system of dichloromethane:methanol:0.88 ammonia (90:10:1) gradually changing to dichloromethane:methanol:0.88 ammonia (70:30:2) to afford the title compound as a colourless oil (702 mg).