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Thionyl chloride (65 ml, 0.89 mol) was added dropwise at ice-cooling for 45 min to a solution of L-proline (57.6 g, 0.50 mol) in 500 ml MeOH. The temperature was raised to reflux. After 4 h at reflux the mixture was cooled and the solvent evaporated in vacuo. MeOH was added to the residue and then evaporated repeatedly three times to give 86 g crude methyl (S)-2-pyrrolidinecarboxylate hydrochloride (99.6% purity by GLC) as a thick syrup. The ester (1.65 g, 0.01 mol) was transferred to a flask containing acetaldehyde (2.21 g, 0.05 mol) 10% Pd/C (0.15 g) and 15 ml MeOH. The mixture was shaken in a Parr apparatus at 55 psi hydrogen pressure for 4 h at room temperature, filtered and evaporated to give 2.1 g crude hydrochloride of the title ester. (91% purity by GLC). This material was subjected to aminolysis in Example 7D.

1. temperatureThe temperature was raised
2. temperatureto reflux
3. temperatureAfter 4 h at reflux the mixture
4. temperaturewas cooled
5. customthe solvent evaporated in vacuo
6. additionMeOH was added to the residue
7. customevaporated repeatedly three times