Water → (2S,3S)-2-[Cbz(methyl)amino]-3-methylpentan-1-ol

Participants

Reaction Steps

To a solution of N-[(benzyloxy)carbonyl]-N-methyl-L-isoleucine (52.37 g, 187.5 mmol, 1 eq.) in tetrahydrofuran (524 mL, 0.35 M) was added borane-tetrahydrofuran complex (1 M in tetrahydrofuran, 375 mL, 375 mmol, 2 eq.) slowly over 1 hour and the reaction was allowed to stir for 18 hours at room temperature. The reaction was cooled to 0° C. and water (30 mL) was added over 30 minutes. The reaction mixture was diluted with 1 M aqueous sodium carbonate solution (100 mL) and tert-butyl methyl ether (250 mL). The aqueous layer was back-extracted with tert-butyl methyl ether (100 mL). The combined organic layers were washed with 1 M aqueous sodium carbonate solution (100 mL), washed with brine (200 mL), dried over magnesium sulfate, filtered, and concentrated in vacuo to provide #1 (48.44 g, 97% yield) as a pale yellow oil, which was used in the next step without further purification. 1H NMR (400 MHz, DMSO-d6), presumed to be a mixture of rotamers: δ 7.26-7.41 (m, 5H), [5.06 (AB quartet, JAB=12.9 Hz, ΔνAB=22.8 Hz) and 5.06 (AB quartet, JAB=9.0 Hz, ΔνAB=9.0 Hz), total 2H], [4.65 (t, J=5.3 Hz) and 4.59 (t, J=5.4 Hz), total 1H], 3.67-3.80 (m, 1H), 3.51-3.60 (m, 1H), 3.41-3.51 (m, 1H), 2.75 and 2.71 (2 s, total 3H), 1.49-1.64 (br m, 1H), 1.24-1.37 (br m, 1H), 0.90-1.02 (br m, 1H), 0.74-0.87 (m, 6H).

Provenance & Evidence