2-Oxazolidinone, 5,5-dimethyl-3-[(2R)-1-oxo-2-[[(phenylmethoxy)amino]methyl]hexyl]-4-(phenylmethyl)-, (4S)- synthesis

Yield:82 % de

Reaction Conditions:

at 20;

Steps:

2.C

Step C: 4S-Benzyl-3-[2-(benzyloxyamino-methyl)-hexanoyl]-5,5-dimethyl-oxazolidin-2-one (p-toluenesulfonic acid salt); 4S-Benzyl-3-(2-butyl-acryloyl)-5,5-dimethyl-oxazolidin-2-one (19.8 g, 62.8 mmol) was mixed with O-benzylhydroxylamine (15.4 g, 126 mmol) and stirred overnight at room temperature. The mixture was dissolved in ethyl acetate and the solution was washed with 1 M hydrochloric acid, 1 M sodium carbonate and brine, dried over anhydrous magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure to afford a pale yellow oil (25.3 g) which was shown by NMR and HPLC analysis to contain 4S-benzyl-3-[2-(benzyloxyamino-methyl)-hexanoyl]-5,5-dimethyl-oxazolidin-2-one (ca. 82% d.e.) along with a trace of starting material. The product was combined with another batch (26.9g, 76% d.e.) and dissolved in ethyl acetate (200 ml). p-Toluenesulfonic acid (22.7 g, 119 mmol) was added and the mixture was cooled to 0 °C. The title compound was obtained as a white crystalline solid by seeding and scratching. Yield: 25.2g, (34%, single diastereoisomer). A second crop (14.7 g, 20%, single diastereoisomer) was also obtained. 1H-NMR;δ (CDCl3), 7.89 (2H, d, J = 8.2 Hz), 7.37-7.12 (10H, m), 7.02 (2H, d, J = 6.9 Hz), 5.28-5.19 (2H, m), 4.55 (1H, m), 4.23 (1H, m), 3.93 (1H, m), 3.58 (1H, m), 2.58 (1H, m), 2.35 (3H, s), 1.67-1.51 (2H, m), 1.29-1.16 (4H, m), 1.25 (3H, s), 1.11 (3H, s), 0.80-0.75 (3H, m).

References:

EP1210330,2005,B1 Location in patent:Page/Page column 11-12