Über die Darstellung der Urocaninsäure

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Abstract
To a soln. of 100 g. 1-histidine-mono-HCl in 750 ml. conc. HC1 is added a soln. of 100 g. NaN02 in 200 ml. H2O drop by drop in 30-54 min., the temp. being kept at 5[degree]. The mixture is cooled, filtered and the filtrate concd. in vacuo. The residue is dissolved in a little warm H2O, and treated with about 400 ml. of 2 N NH3 and evaporated to dryness in vacuo. The a-chloro-B,4-imidazolepropionic acid formed is recrys-tallized from H2O and melts at 172[degree]-180[degree]. Twenty g. of this compound are dissolved in 70 ml. of 33% aqueous trimethyl-amine soln., which is placed in a bomb tube and heated to 60[degree] for 4 hrs. The contents of the tube are refluxed 2 hrs., the mixture cooled and 8-9 g. of sparkling white needle-shaped crystals of urocanic acid (B,4-imidazoleacrylic acid) obtained. The crystals contain 2 mols. H2O and melt at 218[degree]-224[degree]. The anhydrous acid is obtained by heating this compound at 100[degree] for 3 hrs. over H2SO4.

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