To a round bottom flask equipped with a stir bar and charged with (S)-methyl 3-(m-tolyloxy)-2-(tritylamino)propanoate (8.28 g, 18.34 mmol) in MeOH (30 mL) and THF (30 mL) was added lithium hydroxide in water (55.0 mmol, 27.5 mL). The mixture was stirred at room temperature for 1 h. The reaction mixture was neutralized with aq. 2N HCl. The mixture was diluted with EtOAc and the organic phase was isolated and washed with brine; dried over MgSO4; filtered; then concentrated in vacuo. The resulting residue was purified via silica gel chromatography to afford (S)-3-(m-tolyloxy)-2-(tritylamino)propanoic acid, 1.47 g (18%). 1H-NMR (400 MHz, CDCl3) δ 7.44 (d, J=7.1 Hz, 6H), 7.35-7.24 (m, 8H), 7.09 (t, J=7.8 Hz, 1H), 6.76 (d, J=7.6 Hz, 1H), 6.52 (s, 1H), 6.46 (d, J=8.1 Hz, 1H), 4.07 (dd, J=9.2, 2.3 Hz, 1H), 3.71 (t, J=3.2 Hz, 1H), 2.79 (dd, J=9.2, 4.0 Hz, 1H), 2.28 (s, 3H).
