HCID 10470569, compound → L-Glutamic acid, N-((phenylmethoxy)carbonyl)-

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Reaction Steps

N-Benzyloxycarbonyl-glutamic acid-α-ethyl ester. 113 g (0.43 mol) of Z-glu anhydride is dissolved in one liter of anhydrous ethanol and refluxed for 15 hours. The α- and γ-monoethyl esters of Z-Glu are thus formed successively in a ratio of 1:2. The reaction solution is concentrated in vacuo, the oily residue dissolved with 250 ml of anhydrous ether, 78 g of distilled dicyclohexylamine is added, and the mixture is let stand for 2 days in the refrigerator. The crystallizate of the α- and γ-ester.dicyclohexyl ammonium salts is removed with a suction filter and the mother liquor is concentrated in vacuo to recover Z-glu and saponified for 5 hours with 2N NaOH in dioxane at pH 10.5 on the autotitrator. The dicyclohexylammonium salt mixture is dissolved in 300 ml of ethanol to recover the alpha ester, and approximately 1.5 liters of petrol ether (40° C.) is added until turbidity is produced. It is desirable to add a small amount of previously prepared α-ester.dicyclohexylammonium salt as seed crystals. The α-ester.DCA salt crystallizes uniformly (virtually pure on tlc) at 20° C. in the time period from 0.5 to 4 hours, and is recrystallized two more times from ethanol to which petrol ether (40° C.) is added in a ratio of 1:5 until turbidity occurs. All of the mother liquors are worked up as described above for the recovery of Z-Glu. Yield of Z-Glu-α-ethyl ester.DCA salt 34 g (30%) m.p. 154° C. (from a mixture of ethanol and petrol ether (40° C.). RF value in a 7:1 mixture of benzene and glacial acetic acid: 0.50.

Provenance & Evidence