A solution of (2R)-2-[2-(tert-butoxy)-2-oxoethyl]-5-cyclohexylpentanoic acid (Preparation 1) (596 mg, 2.00 mmol) in dichloromethane (8ml) was treated with 1,1′-carbonyldiimidazole (364 mg, 2.25 mol) and the solution was stirred at room temperature for 15 minutes. The N-hydroxyacetamidine (Chem.Ber.; 17; 1884; 2746) (148 mg, 2.00 mmol) was then added and the mixture was stirred for 1 hour. The solvent was removed under reduced pressure and the residue was heated neat under a nitrogen atmosphere for 90 minutes. The crude product was then purified by column chromatography on silica gel eluting with dichloromethane to afford the title compound (385 mg).
