A solution of 2-bromo-4-fluorobenzenesulfonyl chloride (0.57 g) in pyridine (10 mL) was heated to 70° C. and a solution of methyl 7-amino-furo[2,3-c]quinoline-6-carboxylate (Intermediate 16, 0.33 g) in pyridine (10 mL) was added. The mixture was stirred and heated at 70° C. for 4 hours. Further 2-bromo-4-fluorobenzenesulfonyl chloride (0.57 g) was added and the mixture was stirred and heated at 70° C. overnight. After cooling, the mixture was filtered and the solid was washed with methanol. The filtrate was evaporated to dryness and the residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane with a gradient of 15-60%. The product was triturated with diethyl ether and the solid was collected by filtration to give methyl 7-(2-bromo-4-fluorobenzenesulfonylamino)-furo[2,3-c]quinoline-6-carboxylate (0.16 g) as a yellow solid.
