4-Nitrobenzoic Acid → 2-(1-Ethoxycarbonyl-2-vinyl-cyclopropylcarbamoyl)-4-(4-nitro-benzoyloxy)-pyrrolidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

Compound 132 (6.13 g, 16.6 mmol), 4-nitrobenzoic acid (4.17 g, 25 mmol) and PPh3 (6.55 g, 25 mmol) was dissolved in THF (130 ml). The solution was cooled to ˜0° and diisopropyl azidocarboxylate (5.1 g, 25 mmol) was added slowly. The cooling was then removed and the mixture was left over-night at ambient condition. Aqueous sodium hydrogen carbonate (60 ml) was added and the mixture was extracted with dichloromethane. Purification by flash chromatography (pentane-ether, 2:1→pentane-ether, 1:2→2% methanol in ether) gave pure title compound (6.2 g, 72%).

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