Hydrochloric Acid → (2S, 4S)-4-(4-methoxybenzylthio)-2-methylcarbamoylpyrrolidine

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Reaction Steps

52.5 ml of a 4N dioxane solution of hydrogen chloride were added, whilst ice-cooling, to a solution of 4.00 g of (2S, 4S)-1-(t-butoxycarbonyl)-4-(4-methoxybenzylthio)-2-methylcarbamoylpyrrolidine [prepared as described in step (3) above] dissolved in 50 ml of ethyl acetate. The mixture was stirred at 0° to 50° C. for 30 minutes and then at room temperature for 2 hours. At the end of this time, the reaction mixture was poured into a saturated aqueous solution of sodium bicarbonate to make it weakly basic, and it was then extracted with ethyl acetate. The aqueous layer was saturated with ammonium chloride and then extracted with tetrahydrofuran. The extract was washed with an aqueous solution of sodium chloride and dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The residue was purified by column chromatography through silica gel (eluted with a 5:1 mixture by volume of ethyl acetate and methanol), to afford 2.34 g of the title compound as colorless crystals, melting at 53°-54° C.

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