A mixture of (2R,3R)-3-hydroxy-2-(4-phenylcyclohexylmethyl)butanoic acid (3.43 g, 0.012 mol), 2-tetrahydropyranyloxyamine (1.64 g, 0.014 mol), BOP (5.75 g, 0.013 mol), HOBt (1.76 g, 0.13 mol) and NMM (2.63 g, 0.026 mol) in DMF (30 mL) is stirred at 25° C. for 18 h. The mixture is concentrated in vacuo and the residue is taken up in EtOAc. The mixture is washed with ice-cold 0.1 M HCl, saturated aqueous sodium bicarbonate, and saturated aquesous sodium chloride. The organic phase is dried over sodium sulfate and concentrated in vacuo to give 6.02 g of a white solid. Chromatography on silica gel using EtOAc as eluent gives 4.05 g (90%) of (2R,3R)-3-hydroxy-2-(4-phenylcyclohe,(ylmethyl)butanoic acid 2-tetrahydropyranyloxyamide as a white solid.
