Water → 3,7-Dimethoxy-4-phenyl-4H-furo[3,2-b]indole-2-carboxylic acid

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Reaction Steps

A suspension of 11.5 g (0.033 mole) of 3,7-dimethoxy-4-phenyl-4H-furo[3,2-b]indole-2-carboxylic acid methyl ester in 200 ml of 50% aqueous ethanol was treated with 25 ml of 10% aqueous sodium hydroxide solution. After stirring at reflux for 90 minutes, the reaction mixture was cooled and distributed between 750 ml of water and 250 ml of dichloromethane. The insoluble material (primarily the sodium salt of the product) was removed by filtration. The filtrate layers were separated, and the organic layer was discarded. The aqueous layer was washed several times with fresh dichloromethane, cooled in ice, and acidified with 4N hydrochloric acid. The precipitate crude product was filtered and washed with water. The original insoluble sodium salt was stirred for several hours in 400 ml of cold 1N hydrochloric acid, and the product acid was filtered, washed with water, and combined with the material obtained from acidification of the original aqueous layer. The crude yield of the furoindole acid was 9.4 g (85%) yield). A sample recrystallized from acetone/water was analytically pure, mp 148° C. (dec).

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