Citric Acid → [(1S,5S)-7-Methylene-4-oxo-3-[(1R)-1-phenylethyl]-3-aza-bicyclo[3.3.0]octan-1-yl]carboxylic acid tert-butyl ester

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Reaction Steps

A 1 M solution of lithium hexamethyldisilazide in THF (9.15 ml, 9.15 mmol) was added to a solution of (3S)-3-(3-bromo-2-methylene-1-propyl)-5-oxo-1-[(1R)-1-phenylethyl]pyrrolidine-3-carboxylic acid tert-butyl ester (3.22 g, 7.62 mmol) in tetrahydrofuran (76.2 ml) under cooling with ice-acetone in a nitrogen atmosphere, and the mixture was stirred for 10 minutes. A 10% citric acid solution (120 ml) was added to the reaction solution, followed by extraction with ethyl acetate (100 ml×2). The organic layer was washed with brine (200 ml) and dried over anhydrous sodium sulfate. After filtration, the filtrate was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane:ethyl acetate=100:0→95:5→90:10→83:17→80:20→75:25) to give 2.47 g of the title compound as white crystals.

Provenance & Evidence