Hydrochloric Acid → Ethyl 8-benzyloxycarbonylamino-3-ketooctanoate

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Reaction Steps

A solution of 2.65 g (10 mmoles) of 6-benzyloxycarbonylaminohexanoic acid and 1.62 g (10 mmoles) of commercial 1,1'-carbonyldiimidazole in 25 ml of anhydrous tetrahydrofuran was stirred for 15 minutes at room temperature. To the reaction mixture was added a suspension of 6.18 g (40 mmoles) of a white powder of magnesium enolate of monoethyl malonate (prepared from 5.28 g of monoethyl malonate and 972 mg of magnesium) in 50 ml of anhydrous tetrahydrofuran. The mixture was stirred for 2 hours at room temperature. After addition of 50 ml of 1N hydrochloric acid and stirring for 10 minutes, the reaction mixture was extracted 3 times with 50 ml of chloroform. The chloroform layer was washed successively with 1N hydrochloric acid, saturated aqueous sodium hydrogen carbonate solution and saturated saline, then dried over anhydrous sodium sulfate and freed from the solvent by distillation. The residue was passed through a column of 100 g of "Silica Gel 60" (Merck & Co.) and eluted with chloroform (20 g fraction size). Fractions No. 43 to No. 105 were combined and evaporated to dryness to yield 2.35 g (70% yield) of ethyl 8-benzyloxycarbonylamino-3-ketooctanoate.

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