Diisopropylamine → dimethyl (R)-N-tert-butoxycarbonyl-3-isobutyrylaspartate

Participants

Reaction Conditions

Reaction Steps

A solution of 2.61 g (10 m mol) of dimethyl (R)-N-tert-butoxycarbonylaspartate in 10 ml of tetrahydrofuran was added dropwise to a lithium diisopropylamide solution [prepared from 4.62 ml (33 m mol) of diisopropylamine and 21 ml (33 m mol) of butyllithium-hexane solution, in 30 ml of tetrahydrofuran]at -78° C. in a stream of nitrogen, and the mixture was stirred for 10 minutes at -78° C. Then, a solution of 2.76 g (20 m mol) of isobutyrylimidazole in 15 ml of tetrahydrofuran was added dropwise to the reaction mixture, and the mixture was stirred for 10 minutes at -78° C. and further in a dry ice-acetone bath of -40° C. The mixture was further stirred until the temperature reached -20° C., to which a saturated ammonium chloride solution was added and stirred at room temperature. The reaction mixture was diluted with water and and extracted with ethyl acetate. The organic layer was washed with a saturated saline solution, dried over sodium sulfate and distilled. The residue was subjected to a silica gel column (2.5×40 cm) chromatography (ethyl acetate:hexane=1:3→1:2) to obtain 2.07 g (62%) of dimethyl (R)-N-tert-butoxycarbonyl-3-isobutyrylaspartate as colorless oil.

Provenance & Evidence