Hydrochloric Acid → (E)-5-tert-Butoxycarbonylamino-3,5-dimethylhex-2-enoic acid ethylester

Participants

Reaction Steps

Triethyl phosphonoacetate (4.7 g; 20.9 mmol) was dissolved in tetrahydrofuran (36 ml). Potassium tert-butoxide (2.3 g; 20.9 mmol) was added and the reaction mixture was stirred for 40 min at room temperature. (1,1-Dimethyl-3-oxobutyl)carbamic acid tert-butyl ester (2.5 g; 11.6 mmol) was dissolved in tetrahydrofuran (15 ml) and added dropwise to the reaction mixture which was heated to reflux for 12 h. Ethyl acetate (100 ml) and hydrochloric acid (1N; 100 ml) were added and the phases were separated. The aqueous phase was extracted with ethyl acetate (3×50 ml). The combined organic phases were washed with an aqueous solution of sodium hydrogen carbonate (saturated; 100 ml), dried over magnesium sulfate and evaporated in vacuo. The residue was chromatographed on silica (3×40 cm) using ethyl acetate/heptane (1:2) as eluent to afford 2.0 g of (E)-5-tert-butoxycarbonylamino-3,5-dimethylhex-2-enoic acid ethyl ester.

Provenance & Evidence