1,8-Diazabicyclo(5.4.0)undec-7-ene → Methyl 2-(4-{[(benzyloxy)carbonyl]amino}-3-methylphenyl)-5-methyl-1,3-oxazole-4-carboxylate

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Reaction Steps

A solution of methyl 2-(4-{[(benzyloxy)carbonyl]amino}-3-methylphenyl)-5-methyl-4,5-dihydro-1,3-oxazole-4-carboxylate obtained in Example (108c) (4.4 g, 11.5 mmol) in dichloromethane (50 mL) was cooled to 0° C., and bromotrichloroethane (3.20 g, 16.1 mmol) and DBU (2.45 g, 16.1 mmol) were added. The mixture was stirred at the same temperature for three hours, washed with a 1 N aqueous hydrochloric acid solution and brine, and dried over magnesium sulfate. Following concentration, the resulting residue was purified by silica gel column chromatography (elution solvent: ethyl acetate/hexane=1/4, 1/2, 2/2, 2/1) to obtain 1.75 g of the title compound as a colorless solid (40%).

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