A solution of ethyl 5-{(1R)-1-[2-(tert-butoxy)-2-oxoethyl]-4-cyclohexylbutyl}-1,2,4-oxadiazole-3-carboxylate (Preparation 3) (360 mg, 0.91 mmol) and triethylamine (370 mg, 3.65 mmol) in ethanol (5 ml) was treated with N,N-dimethyl-3-azetidinamine (J.Med.Chem.;36; 801; 1993) (300 mg, 0.91 mmol) and the resulting mixture was heated at 80° C. under a nitrogen atmosphere for 16 hours. The mixture was partitioned between ethyl acetate (150 ml) and saturated aqueous ammonium chloride solution (150 ml). The organic layer was washed with saturated ammonium chloride solution (150 ml), water (150 ml) and brine (150 ml), dried over anhydrous sodium sulphate, filtered and the solvent removed under reduced pressure. The residue was purified by column chromatography on silica gel eluting with a gradient system of pentane:ethyl acetate:diethylamine (87.5:12.5:0.25) gradually changing to pentane:ethyl acetate:diethylamine (50:50:1) to afford the title compound as a colourless oil (355 mg).
