Racemate 3-amino-3-(2-methylphenyl)-propionic acid (0.5 g, 2.41 mmol) was used as raw material and dissolved in tert-butyl methyl ether (t-BuOMe, 40 mL). Lipase PSIM (1.2 g, 30 mg/mL) and deionized water (430 μL, 24 mmol) were added, and the reaction mixture was placed in a thermostatic oscillator at 45°C for 7 hr. When the reaction reached 50% conversion, the enzyme was removed by filtration to terminate the reaction. The solvent was removed by distillation under reduced pressure to give unreacted (R)-3-amino-3-(2-methylphenyl)-propionic acid [240 mg, 48%; [α]D25 = +20.1° (c = 0.40, EtOH); ee = 99%]. The filtered enzyme was washed with distilled water (3 x 15 mL) and after evaporation of the aqueous phase, crystalline (S)-3-amino-3-(2-methylphenyl)-propionic acid {200 mg, 48%; [α]D25 = -25° (c = 0.15, H2O); melting point 235-237°C (recrystallized from water); ee = 98%} was obtained. Treatment of (S)-6 or (R)-3 (100 mg) with 18% hydrochloric acid (5 mL) afforded (S)-3-amino-3-(2-methylphenyl)-propionic acid hydrochloride {100 mg, 83%; [α]D25 = -6.4° (c = 0.55, H2O); ee = 99%} or (R)-3-amino-3-(2-methylphenyl)-propionic acid hydrochloride { 96 mg, 92%; [α]D25 = +6.4° (c = 0.3, H2O); ee = 99%}. The 1H NMR (400 MHz, CDCl3, 25°C, TMS) δ (ppm) data of (R)-3 were similar to those of (±)-3. Elemental analysis measured values: C, 69.50; H, 8.42; N, 6.75. 1H NMR (400 MHz, D2O) δ (ppm) data of (S)-6 was similar to that of (R)-6. Elemental analysis measured values: C, 67.02; H, 7.31; N, 7.82.
