[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([N+:8]([O-:10])=[O:9])=[CH:4][C:3]=1[OH:11].[C:12]([O:16][C:17]([N:19]1[CH2:23][CH2:22][CH2:21][C@H:20]1[CH2:24]O)=[O:18])([CH3:15])([CH3:14])[CH3:13].C1C=CC(P(C2C=CC=CC=2)C2C=CC=CC=2)=CC=1.CC(OC(/N=N/C(OC(C)C)=O)=O)C>C1COCC1>[C:12]([O:16][C:17]([N:19]1[CH2:23][CH2:22][CH2:21][C@H:20]1[CH2:24][O:11][C:3]1[CH:4]=[C:5]([N+:8]([O-:10])=[O:9])[CH:6]=[CH:7][C:2]=1[Cl:1])=[O:18])([CH3:15])([CH3:13])[CH3:14]To a solution of 2-chloro-5-nitrophenol (5.06 g, 29.17 mmol), (S)-(−)-1-(tert-butoxycarbonyl)-2-pyrrolidinemethanol (5.87 g, 29.17 mmol), and Ph3P (7.65 g, 29.17 mmol) in 50 mL THF, cooled to −15° C., was added dropwise, over 75 min, a solution of DIAD (6.02 g, 29.75 mmol). The reaction was warmed to RT and stirred for 18 h. The reaction was concentrated to dryness. The crude residue was treated with a small mix of Et2O and hexanes and sonicated so as to triturate out bulk of impurities, which were filtered off. The filtrate was concentrated to dryness. The resulting residue was purified by silica gel column chromatography using 7% EtOAc in hexanes to elute the title compound as a thick yellow oil.
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