Triphenylphosphine → Benzyloxycarbonyl-2-[1-(2,4-dimethoxybenzyl)-2,5-dioxopyrrolidin-3-yl] glycine methyl ester

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In 100 ml of tetrahydrofuran were dissolved 3.2 g of benzyloxycarbonyl-2-(2,5-dioxopyrrolidin-3-yl)glycine methyl ester, 1.8 g of 2,4-dimethoxybenzyl alcohol and 3.9 g of triphenylphosphine and under ice-cooling 2 ml of diethyl azodicarboxylate was added. The mixture was stirred at room temperature for one hour and concentrated under reduced pressure. The residue was dissolved in ethyl acetate, and the solution was washed with 5% sodium hydrogen carbonate and 10% phosphoric acid in that order and dried over sodium sulfate. The solution was concentrated under reduced pressure and the concentrate was chromatographed on a silica gel column, elution being carried out with toluene-ethyl acetate (7:3). The eluate was concentrated under reduced pressure and to the residue was added petroleum ether. The precipitate was collected by filtration and dried. Yield 1.2 g

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