24347-63-5

67-56-1

17407-55-5

24347-63-5

Methanol (14.5 mL, 360 mmol) and p-toluenesulfonic acid monohydrate (0.68 g, 3.6 mmol) were added to a solution of (S)-(+)-2-hydroxy-3-methylbutyric acid (14.20 g, 120 mmol) in carbon tetrachloride (40 mL). The reaction mixture was refluxed under anhydrous conditions for 10 hours. Upon completion of the reaction, the mixture was cooled to room temperature, washed sequentially with water (15 mL) and saturated aqueous sodium bicarbonate solution (10 mL), dried over magnesium sulfate, and concentrated under reduced pressure. Purification of the residue by distillation afforded methyl (S)-2-hydroxy-3-methylbutanoate (13.03 g, 82% yield) as a colorless oil; boiling point 62-63 °C/15 Torr; specific optical rotation [α]D = +23.7 (c 1.00, CHCl3), literature value [α]D = +24.3 (c 1.00, CHCl3); 1H NMR ( CDCl3) δ 0.82 (d, J = 6.9 Hz, 3H, 3-Me), 0.98 (d, J = 6.9 Hz, 3H, 3-Me), 2.03 (m, 1H, 3-H), 2.83 (d, J = 6.2 Hz, 1H, OH), 3.75 (s, 3H, CO2Me), 4.01 (dd, J = 6.2, 3.6 Hz 1H, 2-H); 13C NMR (CDCl3) δ 15.9, 18.6, 32.1, 52.2, 75.0, 175.3; IR (thin film) νmax: 3483, 1735 cm-1.