A solution of methyl 2-((1R)-1-{2-[(benzyloxy)amino]-2-oxoethyl}-4-cyclohexylbutyl)-5-methyl-1,3-oxazole-4-carboxylate (Preparation 72) (152 mg, 0.36 mmol) in dichloromethane (5 ml) was treated sequentially with 1-hydroxybenzotriazole hydrate (48 mg, 0.36 mmol), N-methylmorpholine (82 μl, 0.75 mmol), 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride (75 mg, 0.39 mmol) and dimethylamine hydrochloride (29 mg, 0.36 mmol) and the resulting mixture was stirred at room temperature under a nitrogen atmosphere for 17 hours. The solvent was removed under reduced pressure and the residue was dissolved in ethyl acetate and washed sequentially with water, a saturated aqueous solution of sodium hydrogen carbonate and brine, dried over anhydrous magnesium sulphate, filtered and the solvent removed under reduced pressure. The residue was purified by column chromatography on silica gel eluting with dichloromethane:methanol:0.88 ammonia (95:5:0.5) to afford the title compound as a colourless oil which crystallised on standing (109 mg).
