Synthesis
To an ice-cold stirred solution of ethyl (2S,5S)-1 -[(2S)-2- (methoxycarbonylamino)-3-methyl-butanoyl]-5-methyl-pyrrolidine-2- carboxylate (5.6 g, 17.8 mmol) in ethanol (18 ml) is added a solution of lithium hydroxide monohydrate (17.8 mL of 1.7 M, 30.3 mmol). The reaction mixture is stirred for 5 hours at rt. The reaction mixture is concentrated, diluted with water, washed with ether. The aqueous solution is acidified with aq. 1 N HCl, extracted with CH2CI2. The combined extracts are washed with brine, dried (Na2S04), concentrated to afford (2S,5S)-1 -[(2S)-2-(methoxycarbonylamino)-3- methyl-butanoyl]-5-methyl-pyrrolidine-2-carboxylic acid (5g, 94%) as a white solid.
