反应详情

20 ml of trifluoroacetic acid and subsequently 0.50 ml of trifluoromethanesulfonic acid were added dropwise, whilst ice-cooling, to a solution of 2.0 g of (2S,4S)-4-(4-methoxybenzylthio)-2-[3-methyl-4-(4-nitrobenzyloxycarbonyl)piperazin-1-ylcarbonyl]-1-(4-nitrobenzyloxycarbonyl)pyrrolidine [prepared as described in step (i) above] in 3.08 ml of anisole, and the resulting mixture was stirred at the same temperature for 50 minutes. At the end of this time, the reaction mixture was worked up by the same procedure as described in Preparation 4(ii), to give 1.56 g of the title compound as an amorphous solid.