Hydrochloric Acid → O-(3-Mercaptopropanoyl)glycolic Acid

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Reaction Steps

O-(3-acetylthiopropanoyl)glycolic acid from Example 1 (1.3 g.), under a blanket of argon is treated for fifteen minutes with a cold solution of 7 ml. of water and 7 ml. of concentrated ammonium hydroxide. This is chilled, acidified with concentrated hydrochloric acid and extracted into ethyl acetate, yield: 1.2 g. This product O-(3-mercaptopropanoyl)-glycolic acid is chromatographed on DEAE Sephadex A25 (Polidextrane anion exchange resin) with a linear gradient of ammonium bicarbonate. The desired fractions (45-70; U.V. peak at 254 nm.) are pooled, concentrated and lyophilized. This ammonium salt of O-(3-mercaptopropanoyl)glycolic acid is converted to the free acid by treatment with Dowex 50WX2 cation exchange resin, yield 320 mg. The O-(3-mercaptopropanoyl)glycolic acid is converted to the dicyclohexylamine salt by dissolving in ether and precipitating by the addition of dicyclohexylamine, m.p. 143°-144°.

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