methyl (2S,3S)-3-ethylpyrrolidine-2-carboxylate

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: N-[(tert Butyloxy)carbonyl]-cis, trans-3-ethylproline methyl ester (29.1 g, 0.113 mol) was dissolved in CH3OH (114 mL) with cooling to 0° C., then treated with 1N NaOH (114 mL). After stirring for 20 h at 23° C., the solution was concentrated to remove the CH3OH and then extracted with EtOAc (3×). The organic layers were combined, dried (MgSO4), filtered, and concentrated to give 12.8 g of N-[(tert-Butyloxy)carbonyl]-cis-3-ethylproline methyl ester as an oil. The aqueous layer was acidified with solid citric acid and extracted with EtOAc (2×), the organic layers combined, dried (MgSO4), filtered, and concentrated to give N-[(tert Butyloxy)carbonyl]-trans 3-ethylproline as an oil. 1H NMR (CD3OD) δ3.86 and 3.78 (2 d, 1H, J=6 Hz), 3.33-3.58 (m, 2H), 2.01-2.22 (m, 2H), 1.5-1.74 (m, 2H), 1.33-1.5 (m, 1H), 1.45 and 1.42 (2 s, 9H), 0.98 (t, 3H, J=8 Hz). the solution was concentrated to remove the CH3OH extracted with EtOAc (3×) dried (MgSO4) filtered concentrated