[C:1]([O:5][C:6]([N:8]1[CH2:12][CH2:11][C@H:10]([C@H:13]([OH:16])[CH2:14][OH:15])[CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].[CH2:17](Br)[C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1>C(Cl)Cl.[Ag]=O>[C:1]([O:5][C:6]([N:8]1[CH2:12][CH2:11][C@H:10]([C@H:13]([OH:16])[CH2:14][O:15][CH2:17][C:18]2[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=2)[CH2:9]1)=[O:7])([CH3:4])([CH3:2])[CH3:3]To a solution of (S)-3-((S)-1,2-dihydroxyethyl)pyrrolidine-1-carboxylic acid t-butyl ester (294.0 mg, 1.3 mmol) in DCM (6.3 mL) at room temperature, was added benzyl bromide (181.4 μL, 1525 μmol) followed by silver(II) oxide (472.4 mg, 3.8 mmol). The resulting mixture was stirred overnight. The mixture was filtered and the filtrate was subjected to same amount of silver (II) oxide and benzyl bromide and stirred overnight. The mixture was concentrated and the residue was purified by flash chromatography (12 g silica gel, 0-50% EtOAc/Hexanes). Desired fractions were combined and concentrated to yield the title compound as a colorless oil (165.6 mg).
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