Water → (S)-1-((S)-2-((Methoxycarbonyl)amino)-3-methylbutanoyl)pyrrolidine-2-carboxylic acid

Participants

Reaction Steps

To a mixture of L-proline (4.44 g, 38.6 mmol), water (20 ml), acetonitrile (20 ml) and DIEA (9.5 g, 73.5 mmol) was added a solution of (S)-2,5-dioxopyrrolidin-1-yl 2-(methoxycarbonylamino)-3-methylbutanoate (10 g, 36.7 mmol) in acetonitrile (20 mL) over 10 minutes. The reaction mixture was stirred overnight at room temperature. The solution was concentrated under vacuum to remove the acetonitrile. To the resulting clear water solution was added 6N HCl (9 ml) until pH˜2. The solution was transferred to a separatory funnel and 25% NaCl (10 ml) was added and the mixture was extracted with ethyl acetate (75 ml), and then again with ethyl acetate (6×20 ml), and the combined extracts were washed with 25% NaCl (2×10 ml). The solvent was evaporated to give a thick oil. Heptane was added and the solvent was evaporated to give a foam, which was dried under high vacuum. Diethyl ether was added and the solvent was evaporated to give a foam, which was dried under high vacuum to give (S)-1-((S)-2-(methoxycarbonylamino)-3-methylbutanoyl)pyrrolidine-2-carboxylic acid (10.67 g) as a white solid.

Provenance & Evidence