[C:1]([O:5][C:6]([N:8]1[CH2:12][CH:11]([OH:13])[CH:10]2[N:14]([C:17]([O:19][CH2:20][C:21]3[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=3)=[O:18])[CH2:15][CH2:16][CH:9]12)=[O:7])([CH3:4])([CH3:3])[CH3:2].C1C=CC(P(C2C=CC=CC=2)C2C=CC=CC=2)=CC=1.[N+:46]([C:49]1[CH:57]=[CH:56][C:52]([C:53](O)=[O:54])=[CH:51][CH:50]=1)([O-:48])=[O:47].CC(OC(/N=N/C(OC(C)C)=O)=O)C>C1C=CC=CC=1>[C:1]([O:5][C:6]([N:8]1[CH2:12][CH:11]([O:13][C:53](=[O:54])[C:52]2[CH:51]=[CH:50][C:49]([N+:46]([O-:48])=[O:47])=[CH:57][CH:56]=2)[CH:10]2[N:14]([C:17]([O:19][CH2:20][C:21]3[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=3)=[O:18])[CH2:15][CH2:16][CH:9]12)=[O:7])([CH3:4])([CH3:2])[CH3:3]To a solution of bicyclic alcohol 11 (4.0 g, 11.0 mmol) in benzene (55 mL) at ambient temperature was added Ph3P (5.8 mg, 22.1 mmol) and p-nitrobenzoic acid (3.7 g, 22.1 mmol). DIAD (4.6 mL, 22.1 mmol) was added dropwise via syringe over 1 h, keeping the temperature below 25° C. After 12 h, the reaction mixture was concentrated in vacuo and the residue was purified by flash silica gel chromatography (3:1 to 1:1 hexanes/EtOAc). The partially-purified product (42) was used without further purification. Mass spectrum, m/z [511.9] (M+H)+.
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