Trichloroacetyl isocyanate → (2S,4S)-2-[4-(2-carbamoyloxyethyl)-1-piperazinylcarbonyl]-4-(4-methoxybenzylthio)-1-(4-nitrobenzyloxycarbonyl)pyrrolidine

Participants

Reaction Steps

1.43 ml of trichloroacetyl isocyanate was added, whilst ice-cooling, to a solution of 5.59 g of (2S,4S)-2-[4-(2-hydroxyethyl)-1-piperazinylcarbonyl]-4-(4-methoxybenzylthio)-1-(4-nitrobenzyloxycarbonyl)pyrrolidine in 50 ml of anhydrous methylene chloride, and the resulting mixture was stirred at the same temperature for 30 minutes. At the end of this time, the solvent was removed by distillation under reduced pressure, the resulting residue was dissolved in 120 ml of methanol, and the solution was stirred at room temperature for 4.5 hours in the presence of 35 g of silica gel (a product of Merck & Co., Inc., silica gel 60, 230-400 mesh). The silica gel was removed by filtration, and the filtrate was freed from methanol by evaporation under reduced pressure. The resulting residue was purified by column chromatography through silica gel. Those fractions eluted with an 8:1 by volume mixture of ethyl acetate and methanol were collected and concentrated by evaporation under reduced pressure, to give 5.76 g of the title compound as a colorless powder.

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