Hydrochloric Acid → 4-Hydroxy-4-(3-indolylmethyl)-2-hydroxyiminoglutarate ammonium salt

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Reaction Steps

The above experiment in Example 2 was carried out on a 24-fold scale to prepare an aldol reaction mixture containing 4-hydroxy-4-(3-indolylmethyl)-2-hydroxyiminoglutaric acid. The resulting aldol reaction mixture was adjusted to pH 1.2 by addition of 12N hydrochloric acid and extracted twice with ethyl acetate (100 ml×2). The organic layer was washed with saturated brine, dried with anhydrous magnesium sulfate, filtered to remove the magnesium sulfate, and concentrated with an evaporator to yield the residue. 28% Ammonia water (20 ml) was added, and then 200 ml of ethanol was added, and the mixture was preserved at 5° C. for 3 days. The precipitated crystals were collected by filtration and dried under reduced pressure to yield 4-hydroxy-4-(3-indolylmethyl)-2-hydroxyiminoglutaric acid diammonium salt (2.2 g)(purity 88%; yield 23%). The selectivity for the enantiomer was 44% ee for the 4R isomer.

Provenance & Evidence