Citric Acid → (S)-4-(1-hydroxy-1-methyl-ethyl)-5-oxo-pyrrolidine-1,2-dicarboxylic acid 2-benzylester 1-tert-butyl ester

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Reaction Steps

A solution of lithium hexamethyldisilazide in tetrahydrofuran is cooled to −78° C. and treated with a solution of 15.95 g of (S)-5-oxo-pyrrolidine-1,2-dicarboxylic acid 2-benzyl ester 1-tert-butyl ester in 100 mL of tetrahydrofuran maintaining the temperature at −78° C. The resulting mixture was stirred for 40 minutes and a mixture of 40 mL of acetone and 7 mL of boron trifluoride diethyl etherate added within 20 minutes. The reaction mixture is stirred for 2.5 hours at −78° C. and 300 mL of a 10% solution of citric acid added and the reaction mixture warmed to room temperature. The layers are separated and the aqueous layer is re-extracted with 300 mL of dichloromethane. The combined organic layers are dried, filtered and the solvent removed to give (S)-4-(1-hydroxy-1-methyl-ethyl)-5-oxo-pyrrolidine-1,2-dicarboxylic acid 2-benzylester 1-tert-butyl ester as an oil.

Provenance & Evidence