C(O[CH:4](OCC)[CH2:5][C:6]([NH:8][C:9]1[CH:14]=[C:13]([CH2:15][CH2:16][NH:17][C:18](=[O:23])[C:19]([F:22])([F:21])[F:20])[CH:12]=[CH:11][C:10]=1[O:24][CH3:25])=[O:7])C>S(=O)(=O)(O)O>[CH3:25][O:24][C:10]1[CH:11]=[CH:12][C:13]([CH2:15][CH2:16][NH:17][C:18](=[O:23])[C:19]([F:20])([F:21])[F:22])=[C:14]2[C:9]=1[NH:8][C:6](=[O:7])[CH:5]=[CH:4]2The product of (a) (17.0 g, 42 mmoles) was added cautiously to concentrated sulphuric acid (50 ml) with stirring. When the addition was complete the dark solution was heated at 100° for 45 min then cooled and poured into ice-water. The suspension was extracted with ethyl acetate, and the extracts washed with sodium bicarbonate solution and water, dried and evaporated to give the sub-title compound as a pale yellow solid (11.0 g) mp 181°-184°. A sample recrystallised from ethanol-cyclohexane formed colourless needles mp 185°-186°.
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