反应详情

4.20 g (11.2 mmol) racemic (2R,3R and 2S,3S)-2-dibenzylamino-3-hydroxy-4-phenyl-butyric acid in 14 ml dimethylformamide were added at 0° C. to 1.04 g (23.7 mmol) sodium hydride (55%) in 2.5 ml dimethylformamide. The suspension was stirred for 2 hours and then 2.69 ml (24.6 mmol) 2.5-difluoro-nitrobenzene in 3.5 ml dimethylformamide were added. After stirring overnight at 0° C. the mixture was poured on ice/water. The pH was adjusted to 1 by adding aqueous hydrochloric acid. Extraction with ethylacetate and chromatography on silicagel with dichloromethane/methanol (100:0 to 95:5) yielded 4.02 g (70%) racemic (2R,3R and 2S,3S)-2-dibenzylamino-3-(4-fluoro-2-nitro-phenoxy)-4-phenyl-butyric acid as yellow oil, 1H-NMR (ppm, CDCl3): 2.55–2.63 (m, 1H); 3.54–3.69 (m, 2H); 3.61, 3.66, 3.92, 3.97 (AB, 4H); 4.73–4.80 (m, 1H); 6.14–6.19 (m, 1H); 6.79–6.84 (m,1H); 7.01–7.03 (m, 2H); 7.14–7.16 (m, 3H); 7.2–7.4 (m,11H).

1. stirringAfter stirring overnight at 0° C. the mixture
2. additionwas poured on ice/water
3. extractionExtraction with ethylacetate and chromatography on silicagel with dichloromethane/methanol (100:0 to 95:5)