Dimethyl Sulfide → L-(-)-Tryptophanol

Temperature

70 °C

To a stirred solution of (S)-tryptophan (4.0 g, 20.0 mmol) in THF (100 mL) at 0° C. was slowly added BH3.Me2S complex (5.9 mL, 10M solution in THF, 59.0 mmol). The reaction mixture was heated to 70° C. for 16 h and, after cooling, the excess borane was quenched by the addition of MeOH (10 mL) at 0° C. The reaction mixture was then concentrated in vacuo and the resultant white solid was dissolved in EtOAc (100 mL) and washed with aqueous 20% NaOH solution (2×70 mL). The organic layer was then extracted into aqueous 2M HCl (2×100 mL). The combined acidic aqueous layers were then basified to pH 14 (addition of solid NaOH) and were re-extracted with EtOAc (2×150 mL). The combined organic fractions were washed with brine (70 mL), dried over MgSO4, filtered and concentrated in vacuo to give the title compound (3.5 g, 92%) as a white solid that required no further purification. δH (CD3OD) 7.46 (1H, d, J 7.9 Hz), 7.21 (1H, d, J 8.0 Hz), 6.96 (3H, m), 3.79 (1H, dd, J 11.3 and 3.6 Hz), 3.54 (1H, dd, J 11.2 and 6.2 Hz), 3.05 (1H, m), 2.80 (1H, m), 2.61 (1H, m). Exchangeable protons were not observed.

1. temperatureafter cooling
2. customthe excess borane was quenched by the addition of MeOH (10 mL) at 0° C
3. concentrationThe reaction mixture was then concentrated in vacuo
4. dissolutionthe resultant white solid was dissolved in EtOAc (100 mL)
5. washwashed with aqueous 20% NaOH solution (2×70 mL)
6. extractionThe organic layer was then extracted into aqueous 2M HCl (2×100 mL)
7. additionThe combined acidic aqueous layers were then basified to pH 14 (addition of solid NaOH)
8. extractionwere re-extracted with EtOAc (2×150 mL)
9. washThe combined organic fractions were washed with brine (70 mL)
10. dry with materialdried over MgSO4
11. filtrationfiltered
12. concentrationconcentrated in vacuo

ORD record

ord-b756bf9a69f84fadad55e5ffce5eb329

Source dataset

uspto-grants-2012_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08324204B2