[OH:1][C:2]1[CH:10]=[C:9]2[C:5]([CH:6]=[C:7]([C:11]([OH:13])=[O:12])[NH:8]2)=[CH:4][CH:3]=1.N1C=CN=C1.[CH3:19][C:20]([Si:23](Cl)([CH3:25])[CH3:24])([CH3:22])[CH3:21]>C1COCC1>[C:20]([Si:23]([CH3:25])([CH3:24])[O:1][C:2]1[CH:10]=[C:9]2[C:5]([CH:6]=[C:7]([C:11]([OH:13])=[O:12])[NH:8]2)=[CH:4][CH:3]=1)([CH3:22])([CH3:21])[CH3:19]6-Hydroxy-1H-indole-2-carboxylic acid (5.40 g, 30.48 mmol) is dissolved in THF (100 ml) and imidazole (10.38, 152.4 mmol) is added. The mixture is stirred for 5 minutes, TBDMS-Cl (13.78 g, 91.44 mmol) is added. The reaction is stirred at room temperature for 1 hour. The mixture is filtered into water (200 ml). The solid is washed with THF (50 ml). The filtrate is concentrated to remove THF. The product is extracted with ethyl acetate (100 ml) three times. The organic is dried (MgSO4), filtered, and concentrated to provide 6-(tert-Butyl-dimethyl-silanyloxy)-1H-indole-2-carboxylic acid (8.0 g, 90% yield). 1H NMR (400 MHz, DMSO-d6): δ 12.73 (s, 1H) , 11.43 (s, 1H), 7.49 (d, 1H), 7.00 (s, 1H), 6.84 (s, 1H), 6.63 (m, 1H), 0.97 (s, 9H), 0.20 (s, 6H).
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