[C:1]([O:5][C:6]([N:8]1[CH2:12][C:11](=[CH2:13])[CH2:10][C@H:9]1[C:14](O)=[O:15])=[O:7])([CH3:4])([CH3:3])[CH3:2].CN1CCOCC1.[BH4-].[Na+].CCOCC>C1COCC1.O>[C:1]([O:5][C:6]([N:8]1[CH2:12][C:11](=[CH2:13])[CH2:10][C@H:9]1[CH2:14][OH:15])=[O:7])([CH3:4])([CH3:3])[CH3:2]To 14.7 g (64.7 mmol) (2S)-4-Methylene-pyrrolidine-1,2-dicarboxylic acid 1-tert-butyl ester in 80 ml THF were added 7.13 ml (64.7 mmol, 1.0 eq) N-methylmorpholine and 8.5 ml (64.0 mmol, 1.0 eq) isobutylchloro formate at −5° C. and the solution was stirred at that temperature for 1.5 h. The mixture was filtered and added to a suspension of 3.7 g (97.8 mmol, 1.5 eq) NaBH4 in 30 ml water over a period of 25 min at 0° C. The reaction was stirred at 0° C. for 2 h and at RT over night. Ether was added, the layers were separated and the inorganic layer was extracted with ether and CH2Cl2, the organic layers were washed with brine, dried over Na2SO4, filtered and evaporated, yielding 9.3 g (68%) (2S)-2-Hydroxymethyl-4-methylene-pyrrolidine-1-carboxylic acid tert-butyl ester as light brown oil, MS: 182 (M-CH2OH.).
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