To a stirring mixture of 4-({[(benzyloxy)carbonyl]amino}methyl)cyclohexanecarboxylic acid (750 mg, 2.57 mmol), TBTU (1.08 g, 3.34 mmol), and HOBT (55 mg, 0.03 mmol) in DMF (15 mL) was added the norleucine OMe HCl (411 mg, 2.83 mmol), followed by addition of triethylamine (898 μL, 6.43 mmol). The resulting mixture was then stirred at ambient temperature for 2 hours, diluted with water and the resulting precipitate was collected by filtration and dried in a vacuum oven to provide the titled compound (830 mg, 1.98 mmol, 77%).
