Darstellung und Konstitution des Histidins

The History of the Discovery of the Amino Acids.

“…In 1903 Herzog (270) observed that histidine responds to the biuret test, that it contains no methyl or oxymethyl group, that it withstands oxidation in acid solution, although in alkaline solution it yields hydrocyanic acid, ammonia, and carbon dioxide, and that it can not be brominated. At about the same time Fránkel (267) showed that it contains a carboxyl and an amino group and gives Weidel's pyrimidine reaction. He suggested a constitution based on the pyrimidine ring but, since his formulation contained no asymmetric carbon atom, it was not accepted.…”