[C:1]([O:5][C:6]([NH:8][C@H:9]([CH2:23][CH:24]=[CH2:25])[CH2:10][O:11][CH2:12][C:13]1[CH:22]=[CH:21][CH:20]=[CH:19][C:14]=1[C:15](OC)=[O:16])=[O:7])([CH3:4])([CH3:3])[CH3:2].[Cl-].[Cl-].[Ca+2].[BH4-].[Na+]>CCO.C1COCC1>[C:1]([O:5][C:6](=[O:7])[NH:8][C@H:9]([CH2:23][CH:24]=[CH2:25])[CH2:10][O:11][CH2:12][C:13]1[CH:22]=[CH:21][CH:20]=[CH:19][C:14]=1[CH2:15][OH:16])([CH3:4])([CH3:3])[CH3:2]A solution of compound 18h (4.2 g, 12.0 mmol) in EtOH/THF (30 mL, v/v=1/1) was treated with CaCl2 (5.3 g, 48.0 mmol) and the resulting slurry was cooled under argon in an ice bath. To this mixture was added NaBH4 (3.6 g, 96 mmol) portionwise. After 1 h the ice bath was removed and the reaction mixture was allowed to stir at rt for 16 hr. The mixture was quenched with 10% aq. Na2CO3 and water and the resulting thick, white slurry was extracted with EtOAc (3×50 mL). The combined organic layers were washed with brine, dried over Na2SO4 and concentrated. The crude product was purified by CC to give the desired compound 18i (3.0 g, 78% yield) as yellow oil. LCMS (m/z): 322.1 (MH+).
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