Benzyloxycarbonyl-L-proline → 2-(1,1-Dimethylethyl) 1-(phenylmethyl) (2S)-1,2-pyrrolidinedicarboxylate

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Reaction Steps

The benzyloxycarbonyl-L-proline thus obtained (180 g.) is dissolved in a mixture of dichloromethane (300 ml.), liquid isobutylene (800 ml.) and concentrated sulfuric acid (7.2 ml.). The solution is shaken in a pressure bottle for 72 hours. The pressure is released, the isobutylene is allowed to evaporate and the solution is washed with 5% sodium carbonate, water, dried over magnesium sulfate and concentrated to dryness in vacuo, to obtain benzyloxycarbonyl-L-proline tert.butyl ester, yield 205 g.

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