[OH:1][C:2]([CH3:9])([CH3:8])[C:3]([O:5][CH2:6][CH3:7])=[O:4].[C:10](Cl)(=[O:21])[O:11][C:12]1[CH:17]=[CH:16][C:15]([N+:18]([O-:20])=[O:19])=[CH:14][CH:13]=1>C(#N)C.CN(C1C=CN=CC=1)C.O>[CH3:8][C:2]([O:1][C:10]([O:11][C:12]1[CH:13]=[CH:14][C:15]([N+:18]([O-:20])=[O:19])=[CH:16][CH:17]=1)=[O:21])([CH3:9])[C:3]([O:5][CH2:6][CH3:7])=[O:4]To a solution of ethyl 2-hydroxy-2-methylpropanoate (1.2 g) and 4-nitrophenyl chlorocarbonate (1.2 g) in acetonitrile (20 mL) was added DMAP (0.77 g) at 0° C., and the mixture was stirred at room temperature for 3 days. The mixture was diluted with water, and extracted with ethyl acetate. The extract was washed with water and saturated brine, dried and concentrated under reduced pressure. The residue was separated and purified by silica gel column chromatography (solvent gradient; 0→25% ethyl acetate/hexane) to give ethyl 2-methyl-2-{[(4-nitrophenoxy)carbonyl]oxy}propanoate (1.3 g, 74%) as a pale-yellow oil.
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