[F-].C([N+](CCCC)(CCCC)CCCC)CCC.[NH2:19][C:20]1[C:25]([C:26]([O:28][CH3:29])=[O:27])=[C:24]([OH:30])[C:23]([C:31]2[CH:35]=[CH:34][O:33][C:32]=2[CH2:36][CH2:37][O:38][Si](C(C)(C)C)(C)C)=[CH:22][CH:21]=1>C1COCC1>[NH2:19][C:20]1[C:25]([C:26]([O:28][CH3:29])=[O:27])=[C:24]([OH:30])[C:23]([C:31]2[CH:35]=[CH:34][O:33][C:32]=2[CH2:36][CH2:37][OH:38])=[CH:22][CH:21]=1Tetrabutylammonium fluoride (1M solution in THF, 25 mL) was added to a solution of methyl 6-amino-3-{2-[2-(tert-butyldimethylsilanyloxy)-ethyl]-furan-3-yl}-2-hydroxybenzoate (Intermediate 29, 1.34 g) in THF (75 mL) and the mixture was stirred for 1 hour. The mixture was evaporated to dryness and water and ethyl acetate were added. The organic layer was separated, dried (MgSO4) and filtered. 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 0-50% to give methyl 6-amino-2-hydroxy-3-[2-(2-hydroxyethyl)-furan-3-yl]-benzoate (0.88 g) as a yellow gum.
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