CAS 4668-42-2 Z-ASP-OME products price,suppliers

49.0 g (196 mmol) of (S)-benzyl(2, 5-dioxotetrahydrofuran-3-yl)carbamate obtained in Step 1-1(2) was dissolved in 100 mL of ethyl acetate, and then 150 mL of methanol was added thereto, followed by stirring at room temperature for 5 hours. The mixture was dried under vacuum and dissolved in 200 mL of diisopropylether, and 34 mL of dicyclohexylamine was slowly added dropwise under stirring. The produced salt of (S)-3-((benzyloxycarbonyl)amino)-4-methoxy-4-oxobutanoic acid dicyclohexylamine was filtered, and suspended in 200 mL of distilled water. 200 mL of ethyl acetate was added thereto, and was adjusted to pH 2 with 6 N hydrochloric acid. After phase-separation, the organic layer was washed several times with distilled water, and dried over magnesium sulfate, followed by concentration under reduced pressure. 200 mL of diethyl ether and 20 mL of petroleum ether were added to the residual concentrate for crystallization. The produced crystals were filtered to give 32.3 g of the title compound (yield: 54percent).