[C:1]([O:5][C:6]([N:8]1[CH2:17][CH2:16][C:15]2[C:10](=[CH:11][CH:12]=[CH:13][CH:14]=2)[CH:9]1CO)=[O:7])([CH3:4])([CH3:3])[CH3:2].N1C=CC=C[CH:21]=1.[Br-:26].[Br-].C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1>C(Cl)Cl>[C:1]([O:5][C:6]([N:8]1[CH2:17][CH2:16][C:15]2[C:10](=[CH:11][CH:12]=[C:13]([CH2:21][Br:26])[CH:14]=2)[CH2:9]1)=[O:7])([CH3:2])([CH3:3])[CH3:4]A solution of intermediate 24-95 (2.0 g, 7.6 mmol) and pyridine (1.2 mL, 11 mmol) in DCM (100 mL) is treated in one portion with triphenylphosphine dibromide (4.8 g, 11 mmol) at 0° C. The mixture is allowed to stir for 30 min, then concentrated in vacuo. The resulting crude material is purified by column chromatography on silica gel (using a gradient of 5-60% EtOAc/heptane) to afford the title compound (2.2 g).
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