A solution of (3R)-6-cyclohexyl-3-[4-(methoxycarbonyl)-5-methyl-1,3-oxazol-2-yl]hexanoic acid (Preparation 174) (2.48 g, 7.36 mmol) was cooled to 0° and treated with 1-hydroxybenzotriazole hydrate (994 mg, 7.36 mmol), 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride (2.12 g, 11.06 mmol) and N-methylmorpholine (1.21 ml, 11.04 mmol). The mixture was stirred for 15 minutes then treated with O-benzylhydroxyamine (1.17 g, 7.36 mmol) and further N-methylmorpholine (0.81 ml, 7.36 mmol). The mixture was stirred for 1 hour being allowed to warm to room temperature over this time. The solvent was removed under reduced pressure and the residue was dissolved in ethyl acetate, washed sequentially with water, a saturated solution of sodium hydrogen carbonate and brine, dried over anhydrous magnesium sulphate, filtered and the solvent removed under reduced pressure to afford the title compound as a colourless oil (3.22 g).
