[Br:1][C:2]1[C:3]([CH3:23])=[C:4]([NH:8][CH2:9][C:10]2[CH:14]=[C:13]([C:15]([CH3:18])([CH3:17])[CH3:16])[S:12][C:11]=2[C:19]([O:21]C)=[O:20])[CH:5]=[CH:6][CH:7]=1.C1COCC1.CO.[OH-].[Li+]>O>[Br:1][C:2]1[C:3]([CH3:23])=[C:4]([NH:8][CH2:9][C:10]2[CH:14]=[C:13]([C:15]([CH3:17])([CH3:18])[CH3:16])[S:12][C:11]=2[C:19]([OH:21])=[O:20])[CH:5]=[CH:6][CH:7]=1
A 50-mL single-necked round-bottomed flask equipped with a magnetic stirrer was charged with 101d (1.30 g, 3.28 mmol), THF (5.0 mL), methanol (5.0 mL) and water (5.0 mL). Lithium hydroxide (1.38 g, 32.8 mmol) was added and the mixture was placed in a 40° C. oil bath. After 16 h the reaction mixture was cooled to room temperature and the volatiles removed under reduced pressure. The resulting aqueous solution was acidified with 2 N hydrochloric acid to pH of 4. The resulting solid was filtered off and dried in a vacuum oven at 40° C. affording a quantitative yield (1.25 g) of 101e as a white solid: mp 150-152° C.; 1H NMR (300 MHz, DMSO-d6) δ 6.85 (t, 1H, J=7.8 Hz), 6.75-6.67 (m, 3H), 4.35 (s, 2H), 2.18 (s, 3H), 1.26 (s, 9H); MS (APCI−) m/z 380.2 (M−H).
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