Br[C:2]1[CH:7]=[C:6]([NH:8][C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])[CH:5]=[CH:4][C:3]=1[NH:16][C:17](=[O:23])[O:18][C:19]([CH3:22])([CH3:21])[CH3:20].C[CH2:25][O:26]CC.C([Li])(C)(C)C.CN(C)C=O>O1CCCC1.O>[C:12]([O:11][C:9]([NH:8][C:6]1[CH:5]=[CH:4][C:3]([NH:16][C:17](=[O:23])[O:18][C:19]([CH3:22])([CH3:21])[CH3:20])=[C:2]([CH:25]=[O:26])[CH:7]=1)=[O:10])([CH3:15])([CH3:14])[CH3:13]
3.3 g (0.01 mole) of tert.butyl (2-bromo-4-tert.butoxycarbonylaminophenyl)carbamate from step A was dissolved in 100 mL of anhydrous tetrahydrofuran under argon. Then, 17 mL (0.03 mole) of a 1.6-molar ether solution of methyllitrium was added stepwise. The reaction mixture was cooled to −20° C. and to it was added stepwise 7 mL (0.01 mole) of a 1.5-molar tert.butyllithium solution. At the end of the addition, the solution was allowed to agitate for an additional 30 min at −20° C. Then, 1.2 g (0.02 mole) of dimethylformamide was added, and the reaction mixture was allowed to agitate for one hour at −20° C. The reaction mixture was then slowly warmed up to room temperature, hydrolyzed with water and poured onto diethyl ether. The aqueous phase was then extracted with diethyl ether, and the organic phase was dried with magnesium sulfate. The solvent was distilled off in a rotary evaporator, and the residue was purified on silica gel with petroleum ether/ethyl acetate (9:1).
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