Hydrochloric Acid → (4S)-4-hydroxy-4-(3-indolylmethyl)-2-hydroxyiminoglutaric acid

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Reaction Steps

44.7 g (0.131 mol) of the ammonium salt of 4-hydroxy-4-(3-indolylmethyl)-2-hydroxyiminoglutaric acid was dissolved in 500 ml of water at 25° C. The resulting aqueous solution was adjusted to pH 2, using 25.5 g of 36% hydrochloric acid. The acidic solution was extracted in 1300 ml of ethyl acetate. The ethyl acetate solution was rinsed with 200 ml of aqueous saturated sodium chloride. 500 ml of aqueous sodium carbonate solution (13.9 g (0.131 mol) of sodium carbonate) was added to the resulting ethyl acetate solution, for agitation to separate the aqueous alkaline solution from ethyl acetate. 23.1 g of 36% hydrochloric acid was added to the resulting aqueous alkaline solution to adjust the solution to pH 2. (R)-(+)-1-phenylethylamine of 6.99 g (57.6 mmol) is dropwise added to the resulting acidic solution, for agitation at 25° C. for one hour. The resulting crystal was filtered and dried under reduced pressure, to obtain the (R)-(+)-1-phenylethylaine salt (21.8 g; 47.8 mmol) of (4S)-4-hydroxy-4-(3-indolylmethyl)-2-hydroxyiminoglutaric acid (at a yield of 72.7% and optical purity of 87.4%).

Provenance & Evidence