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Approximately 13.2 grams (0.0336 mole) of benzyl leucinate p-toluenesulfonate is treated with sodium bicarbonate to provide benzyl leucinate, which is recovered by methylene chloride extraction. In a 200 ml 3 neck flask equipped with a nitrogen gas inlet and outlet adaptors and a magnetic stirrer, 6.25 grams (0.34 mole) of dicyclohexylcarbodiimide is dissolved in 30 milliliters of freshly distilled dry CH2Cl2, and the recovered benzyl leucinate is added thereto. The mixture is maintained under a nitrogen atmosphere and is cooled to approximately -30° C. using dry ice and carbon tetrachloride. To the mixture 7.45 grams (0.0336 mole) of N-α-t-butyloxycarbonylvaline dissolved in 50 ml of dry CH2Cl2 is added dropwise. The resulting mixture is stored at -10° C. for 2 days. After removing a resultant white precipitate by filtration, the methylene chloride layer is washed successively with 25 percent aqueous acetic acid, aqueous sodium bicarbonate solution, water, and saturated aqueous saline solution. The organic layer is then dried over anhydrous MgSO4 and the solvent is removed in vacuo. The residue is taken up in ethyl acetate, filtered, and again concentrated in vacuo. The resulting white solid is recrystallized from ethanol/hexane to yield in two crops 9.17 grams of benzyl N-α-t-butyloxycarbonylvalylleucinate (65% yield) having a melting point of 90°-91° C.