[C:1]([N:8]1[CH2:11][CH:10]([OH:12])[CH2:9]1)([O:3][C:4]([CH3:7])([CH3:6])[CH3:5])=[O:2].[H-].[Na+].[N+:15]([C:18]1[CH:23]=[CH:22][C:21](F)=[CH:20][C:19]=1[CH3:25])([O-:17])=[O:16]>C1COCC1>[C:4]([O:3][C:1]([N:8]1[CH2:11][CH:10]([O:12][C:21]2[CH:22]=[CH:23][C:18]([N+:15]([O-:17])=[O:16])=[C:19]([CH3:25])[CH:20]=2)[CH2:9]1)=[O:2])([CH3:7])([CH3:6])[CH3:5]In a dry flask, N-Boc-3-hydroxy-azetidine (9.8 g, 57 mmol) was dissolved in 200 mL of dry THF. The solution was cooled with an ice-water bath and sodium hydride (2.0 g, 83.mmol) was added in several portions. The suspension was stirred for an additional 0.5 hours, then 7.9 g of 2-nitro-5-fluorotoluene (7.9 g, 51 mmol) in 100 mL of dry THF was added dropwise. The solution was stirred overnight at room temperature. The THF was removed under vacuum and the residue was partitioned between ethyl acetate and water (100 mL each). The organic layer was collected and the aqueous layer was subsequently extracted twice with ethyl acetate. The combined organic layers were washed with 1 N HCl, water, saturated sodium bicarbonate and brine (50 mL each). The organic layer was dried over anhydrous sodium sulfate, concentrated. The residue was purified by silica gel column (EtOAc/Hexanes 1:19→1:4 gradient) to give 12.0 g (43 mmol, 84% yield) of the title compound, which was used directly in the next step. MS: 309 (M++1).
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