反应详情

A solution of 42 g (148 mmol) dibenzylamino-acetic acid ethyl ester in 1 l tetrahydrofuran was stirred at −70° C. with 87 ml (77.6 mmol) lithium diisopropylamide (2M in tetrahydrofurane) for 60 minutes. 28.7 g (175 mmol) 3-(Benzyloxy)propanal were added and stirring was continued overnight. The mixture was allowed to warm to room temperature and 200 ml saturated aqueous ammonium chloride solution was added. Extraction with diethylether and chromatography on silicagel with ethylacetate/heptane 0:100 to 100:0 yielded as first eluting fraction 13.0 g (20%) racemic (2S,3R and 2R,3S)-5-benzyloxy-2-dibenzylamino-3-hydroxy-pentanoic acid ethyl ester, MS m/e (%): 448.1 (M+H+, 100) and as second diluting fraction 11.0 g (17%) racemic (2R,3R and 2S,3S)-5-benzyloxy-2-dibenzylamino-3-hydroxy-pentanoic acid ethyl ester, MS m/e (%): 448.1 (M+H+, 100).

1. extractionExtraction with diethylether and chromatography on silicagel with ethylacetate/heptane 0:100 to 100:0