Acetic Acid → 4-Ethyl-2-(2-hydroxy-1-phenyl-ethylamino)-2-methyl-hexanoic acid

Temperature

-78 °C

To a solution of (5S)-3-methyl-5-phenyl-5,6-dihydro-2H-[1,4]oxazin-2-one (5 g, 26.4 mmol, see WO-A-02/051983) in anhydrous 2-methyltetrahydrofuran (50 ml) was added boron trifluoride tetrahydrofuran complex (5.8 ml, 52.8 mmol) with stirring under nitrogen at −78° C. The resultant solution was then stirred at −78° C. for 1 hour. (2-Ethylbutyl)magnesium bromide as a solution in tetrahydrofuran (170 ml, 0.16 M, 27.7 mmol) was then added maintaining the temperature below −60° C. during the addition. The resultant solution was stirred at −78° C. for a further 2 hours. Acetic acid (0.6 ml 10.6 mmol) was then added and the solution warmed to 22° C. Saturated aqueous ammonium chloride (50 ml) was then added followed by water (100 ml). The phases were separated and the organic phase retained. The resultant solution was then distilled to dryness under vacuum. Toluene (75 ml) was then added and the organic solution was washed with water (25 ml) then saturated aqueous sodium chloride solution (25 ml) and the phases separated and the organic phase retained. Aqueous hydrochloric acid (100 ml, 1.5 M) was then added and the resultant biphasic mixture warmed to 30° C. and stirred for 2 hours. The phases were separated and the aqueous phase retained. Aqueous sodium hydroxide (47% w/w, 6 ml then 2M, 16 ml) was then added to give a pH of 5 by pH paper. The resultant slurry was stirred at 22° C. for 30 minutes and the solid was then isolated by filtration. The filter cake was washed with water (25 ml) and dried at 60° C. overnight under vacuum to give the title compound (4.1 g crude weight, 95% purity, 14.0 mmol, 53% yield): mp 149° C.; 1H-NMR (CD3OD, 300 MHz), δ: 0.83 (3H, t), 0.90 (3H, t), 1.06 (3H, s), 1.31-1.54 (5H, m) 1.73 (2H, d), 4.40 (1H, t), 7.46-7.50 (5H, m); LRMS (ES): m/z 293 [M]+.

1. temperaturemaintaining the temperature below −60° C.
2. additionduring the addition
3. temperaturethe solution warmed to 22° C
4. customThe phases were separated
5. distillationThe resultant solution was then distilled to dryness under vacuum
6. additionToluene (75 ml) was then added
7. washthe organic solution was washed with water (25 ml)
8. customsaturated aqueous sodium chloride solution (25 ml) and the phases separated
9. additionAqueous hydrochloric acid (100 ml, 1.5 M) was then added
10. temperaturethe resultant biphasic mixture warmed to 30° C.
11. stirringstirred for 2 hours
12. customThe phases were separated
13. additionAqueous sodium hydroxide (47% w/w, 6 ml then 2M, 16 ml) was then added
14. customto give a pH of 5 by pH paper
15. stirringThe resultant slurry was stirred at 22° C. for 30 minutes
16. customthe solid was then isolated by filtration
17. washThe filter cake was washed with water (25 ml)
18. customdried at 60° C. overnight under vacuum

ORD record

ord-8c209e4e55a244dea7aef4817db1c3db

Source dataset

uspto-grants-2009_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07612226B2