Potassium Hydroxide → Medica 16

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Reaction Steps

A mixture of 17.0 g of the tetra-ester of Example 1 and 300 ml of a 25% aqueous KOH solution was heated in an oil bath to reflux temperature and the mixture was refluxed until the organic phase has completely disappeared (about 48 hours). The aqueous solution was then cooled to room temperature, extracted with ether, further cooled by the addition of ice and acidified with concentrated aqueous hydrochloric acid, whereupon a solid precipitate was formed consisting of the corresponding tetracarboxylic acid. This solid precipitate was dissolved in diethyl ether and the solution dried over anhydrous magnesium sulfate, filtered and evaporated to dryness. The tetracarboxylic acid residue was decarboxylated by heating to 150°-160° C. on an oil bath until evolution of carbon dioxide was no longer observed. The crude product was cooled and recrystallized from a mixture of chloroform and petroleum ether (40°-60° C.). The pure product was obtained at a yield of 5.5 g.

Provenance & Evidence