Benzyloxycarbonyl-L-proline → (S)-1-Benzyl 2-methyl pyrrolidine-1,2-dicarboxylate

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Reaction Steps

To a solution of N-Cbz-proline (140 g, 562 mmol) in methanol (850 mL) was added p-toluenesulfonic acid monohydrate (5 g, 26 mmol). The solution was heated to reflux and stirring continued for 12 h. The heating mantle was removed, and after cooling to room temperature, the solvent was removed by rotary evaporation. The residue was dissolved in ethyl acetate (500 mL), and washed twice with saturated aqueous NaHCO3 (300 mL), twice with brine (200 mL), dried with MgSO4 filtered and concentrated to give a colorless oil (129 g, 88% yield)

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