Dicyclohexylcarbodiimide → 1-(4-methoxycarbonyl-2-methylbutanoyl)-L-proline tert.-butyl ester

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Reaction Steps

4-Methoxycarbonyl-2-methylbutanoic acid (3.1 g.) and L-proline tert.-butyl ester (3.78 g.) are dissolved in dichloromethane (40 ml.). The solution is chilled with stirring in an ice bath and dicyclohexylcarbodiimide (4.12 g.) is added. After stirring 15 minutes in the ice bath and 18 hours at room temperature, the precipitate is filtered off and the filtrate is concentrated to dryness in vacuo. The residue is chromatographed on a column of silica gel with chloroform to obtain 1-(4-methoxycarbonyl-2-methylbutanoyl)-L-proline tert.-butyl ester, yield 3.5 g.

Provenance & Evidence