13139-16-7

141321-52-0

N-Boc-L-isoleucine (13.86 g, 60 mmol) was dissolved in THF (150 mL) under argon protection and cooled to 0°C. A 1 M BH3-THF solution (90 mL, 90 mmol) was slowly added dropwise over 20 min. After keeping 0 °C and continuing to stir for 30 min, the reaction mixture was allowed to gradually warm up to room temperature and stirred for 5 h. The reaction was then carried out at 0 °C for 5 min. Upon completion of the reaction, the mixture was again cooled to 0 °C and water was added dropwise to quench the reaction. Most of the THF was evaporated under reduced pressure and the residue was extracted by adding ethyl acetate (180 mL) and water (60 mL) to the residue. The organic layer was separated, washed sequentially with water (50 mL) and saturated brine (50 mL), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give N-Boc-D-isoleucinol (12.89 g, 99% yield) as a colorless oil. The product could be used in the next reaction without further purification. [α]25D +14.8 (c 1.0, MeOH); 1H NMR (400 MHz, CDCl3) δ 5.04 (dd, J=48.3, 13.9 Hz, 1H), 3.73-3.55 (m, 2H), 3.48 (s, 1H), 3.37 (s, 1H), 1.58 (d, J=14.5 Hz, 1H). 1.56-1.48 (m, 1H), 1.45 (s, 9H), 1.23-1.05 (m, 1H), 0.91 (t, J=7.1 Hz, 6H); 13C NMR (100 MHz, CDCl3) δ 156.7, 79.3, 63.4, 56.8, 35.9, 28.4, 25.3, 15.5, 11.4; HRMS (ESI) m/z: [M+Na]+ calculated value C11H23NO3Na 240.1570, measured value 240.1530.