[NH:1]1[CH2:6][CH2:5][O:4][CH2:3][CH2:2]1.[C:7]([N:14]1[CH2:20][CH2:19][CH2:18][C@H:15]1[CH:16]=O)([O:9][C:10]([CH3:13])([CH3:12])[CH3:11])=[O:8].N1C=CC=CC=1.B>C(Cl)Cl.[Cl-].[Zn+2].[Cl-]>[N:1]1([CH2:16][C@@H:15]2[CH2:18][CH2:19][CH2:20][N:14]2[C:7]([O:9][C:10]([CH3:11])([CH3:13])[CH3:12])=[O:8])[CH2:6][CH2:5][O:4][CH2:3][CH2:2]1Part A. Morpholine (7.1 g, 7.1 mL, 82 mmol) was added to a stirring solution of N-BOC-(S)-prolinal (3.3 g, 17 mmol) in methylene chloride (83 mL) followed by zinc chloride (0.5 M in THF, 100 mL, 50 mmol). After stirring at ambient temperature for 5 h, borane-pyridine (ca. 8 M, 2 mL, 16 mmol) was added. After stirring at ambient temperature overnight, the reaction was evaporated in vacuo. Methanol was added to the residue and the solids were filtered. Evaporation of the filtrate afforded 13 g of crude product. Purification over silica gel afforded 3.9 g (87%) of 1,1-dimethylethyl (S)-2-(4-morpholinylmethyl)-1-pyrrolidinecarboxylate: 1H-NMR (CDCl3) δ 3.90 (1H, m), 3.69 (4H, m), 3.34 (2H, m), 2.57 (2H, m), 3.40 (2H, m), 2.18 (1H, m), 1.90 (4H, m), 1.74 (1H, m), 1.47 (9H, s).
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