[CH2:1]([Li])CCC.[C:6]([O:10][C:11]([N:13]1[CH2:17][CH2:16][CH:15]([CH:18]=O)[CH2:14]1)=[O:12])([CH3:9])([CH3:8])[CH3:7]>[Br-].C[P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1.C1COCC1>[C:6]([O:10][C:11]([N:13]1[CH2:17][CH2:16][CH:15]([CH:18]=[CH2:1])[CH2:14]1)=[O:12])([CH3:9])([CH3:8])[CH3:7]To a suspension consisting of methyl triphenylphosphonium bromide (4.76 g, 13.3 mmol) and THF (20 mL) at 0° C. was added n-butyl lithium (1.6 M solution in hexanes, 8.3 mL). The resulting orange solution was stirred at 0° C. for 5 min. A solution consisting of 3-formyl-pyrrolidine-1-carboxylic acid tert-butyl ester (2.50 g, 12.5 mmol) and THF (15 mL) was then added via cannula. The reaction mixture was stirred at 0° C. and was warmed to rt over 2.5 h. The reaction mixture was then cooled to 0° C., quenched with sat. NH4Cl, and extracted with Et2O. The organic layer was combined, dried (MgSO4) and concentrated. The crude residue was suspended in hot hexanes and filtered. The filtrate was concentrated and purified (FCC) to give the title compound (1.7 g, 70%).
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