Imidazole → (3S)-3-[3-(tert-Butyldimethylsilyloxy)-1-propyl]-5-oxo-1-[(1R)-1-phenylethyl]pyrrolidine-3-carboxylic acid tert-butyl ester

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Reaction Steps

(3S)-3-(3-Hydroxy-1-propyl)-5-oxo-1-[(1R)-1-phenylethyl]pyrrolidine-3-carboxylic acid tert-butyl ester (46 g) and imidazole (11.9 g) were dissolved in dimethylformamide (600 mL). After addition of tert-butyldimethylsilyl chloride (23.2 g) under ice-cooling, the mixture was stirred at room temperature for 59.5 hours. The reaction solution was extracted with a 10% citric acid solution and ethyl acetate. Then, the organic layer was sequentially washed with saturated sodium bicarbonate water and brine, dried over anhydrous sodium sulfate, and filtered. Thereafter, the solvent was evaporated under reduced pressure. The residue was subjected to silica gel column chromatography (hexane:ethyl acetate=9:1→8:2→2:1) to give 29.7 g of the title compound as a pale yellow oil.

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