Formic Acid → 7-[2-((Z)-3-diethylaminoprop-1-enyl)-4-fluorobenzenesulfonyl-amino]-2,3,9,9a-tetrahydro-1H-pyrrolo[1,2-a]indole-8-carboxylic acid

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A mixture of methyl 7-[2-((Z)-3-diethylaminoprop-1-enyl)-4-fluorobenzenesulfonylamino]-2,3,9,9a-tetrahydro-1H-pyrrolo[1,2-a]indole-8-carboxylate (Intermediate 27, 0.311 g) and lithium hydroxide monohydrate (0.526 g) in dioxane (10 mL) and water (2.5 mL) was irradiated in the microwave at 135° C. for 45 minutes. After cooling, the mixture was diluted with methanol and acidified with formic acid. The mixture was concentrated in vacuo and the residue was diluted with ethanol and toluene and again concentrated in vacuo. The residue was triturated with methanol in DCM (20% solution) and filtered. The filtrate was concentrated in vacuo and the residue was purified by chromatography on silica, eluting with a mixture of methanol and DCM with a gradient of 0-20%. The resultant solid was triturated with ethyl acetate to give a pale yellow solid which was purified by preparative HPLC (C18), eluting with a mixture of acetonitrile and water, containing 0.1% formic acid with a gradient of 5-70% to give 7-[2-((Z)-3-diethylaminoprop-1-enyl)-4-fluorobenzenesulfonyl-amino]-2,3,9,9a-tetrahydro-1H-pyrrolo[1,2-a]indole-8-carboxylic acid (0.090 g).

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