To a solution of methyl N-(tert-butoxycarbonyl)-5-methyl-l-norleucinate (980 mg, 3.78 mmol) in THF (30 mL) at 0 °C was added a solution (precooled to 5 °C) of LiOH (1 M, 11.3 mL, 11.33 mmol), and the resulting mixture was stirred at 0 °C for 1 h and then allowed to warm to an ambient temperature. The reaction was acidified to pH 2 with 1 M hydrochloric acid and extracted with ethyl acetate (3 × 60 mL). The combined organics were washed with brine (100 mL), dried over MgSO4, filtered, and the solvent was removed in vacuo to yield the title compound as a clear oil, 990 mg, 99%. 1H NMR (400 MHz, CDCl3) δ 4.96 (d, J = 7.8 Hz, 1H), 4.23–4.34 (m, 1H), 1.75–1.93 (m, 2H), 1.60–1.72 (m, 1H), 1.50–1.59 (m, 1H), 1.44 (s, 9H), 1.19–1.30 (m, 1H), 0.88 (d, J = 4 Hz, 3H), 0.86 (d, J = 4 Hz, 3H); MS (API-ES+) for C12H23NO4m/z 268.1 (M + Na)+.