A solution of (2R)-2-(2-tert-butoxy-2-oxoethyl)-5-cyclohexylpentanoic acid (preparation 168) (500 mg, 1.67 mmol) in DCM (20 ml) was treated with HOBt (227 mg, 1.67 mmol), NMM (203 μl, 1.85 mmol) and WSCDI (354 mg, 1.85 mmol) followed by tert-butyl (2S)-2-[(Z)-amino(hydroxyimino)methyl]-1-piperidinecarboxylate (WO 9945006) (406 mg, 1.67 mmol) and stirred at room temperature, under a nitrogen atmosphere for 18 hours. H2O (10 ml) was added and after 10 minutes the reaction mixture was separated in a 5 micron filter cartridge. The solvent was removed under reduced pressure to afford the title compound as a colourless foam.
