Thionyl Chloride → tert-butyl (4S)-1-methyl-3-[(2S)-3-benzoylthio-2-methylpropionyl]-2-oxo-imidazolidine-4-carboxylate

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Reaction Conditions

Reaction Steps

3.0 g of tert.-butyl (4S)-1-methyl-2-oxo-imidazolidine-4-carboxylate are dissolved in 20 ml of tetrahydrofuran. 1.7 g of potassium tert.-butoxide are added to the solution under cooling at about -30° C. and stirring, and the mixture is further stirred at the same temperature for 10 minutes. A solution of (2S)-3-benzoylthio-2-methylpropionyl chloride (prepared by heating the mixture of 3.4 g of (2S)-3-benzoylthio-2-methylpropionic acid and 10 ml of thionyl chloride at 50°-60° C. for 2 hours and then evaporating excess thionyl chloride under reduced pressure) in 10 ml of tetrahydrofuran is added dropwise to the mixture under ice-cooling and stirring. Then, said mixture is further stirred at room temperature overnight. After the reaction, the mixture is condensed under reduced pressure, and the residue is dissolved in ethyl acetate. The ethyl acetate solution is washed with water and an aquous sodium bicarbonate solution, dried and then evaporated to remove solvent. The oily residue thus obtained is purified by silica gel column chromatography (Solvent, toluene-ethyl acetate(20:1)). 4.5 g of tert-butyl (4S)-1-methyl-3-[(2S)-3-benzoylthio-2-methylpropionyl]-2-oxo-imidazolidine-4-carboxylate are obtained as colorless crystals. Yield: 73.9% M.p. 128° C.

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