THE SYNTHESIS OF INACTIVE PARA- AND ANTI-HYDROXYASPARTIC ACIDS (AMINOMALIC ACIDS)

Abstract

The increasing recognition of the importance of the hydroxyamino-acids in protein chemistry is an incentive to their more complete investigation.The particular case of hydroxyaspartic acid or aminomalic acid is of interest for several reasons.It represents the lower homologue of p-hydroxyglutamic acid already identified as a constituent of various proteins, and hence itself may not improbably be found among the proteins.Indeed Skraup (1) in 1904 stated that he had actually found hydroxyaspartic acid among the products of hydrolysis of casein.A careful perusal of Skraup's description of t'he supposedly new amino-acid does not lead to much confidence in the accuracy of the deductions drawn.In the first place the experiments are described in a fashion which makes repetition imppssible; secondly no evidence is adduced that the substance in question was a dibasic acid, neither are molecular weight, optical rotation, nor a complete analysis recorded.The substance is stated to be sparingly soluble in cold water, and melts at 305-320".A copper salt of supposedly normal constitution containing 3.5 to 4 molecules of water of crystallization, was analyzed for carbon and hydrogen, while a single nitrogen determination was made on 86 mg. of the free acid.Without further analytical or chemical evidence Skraup concludes, "ES liegt dkmnach bestimmt die Oxyamidobernsteins&ure vor, die bisher iiberhaupt noch nicht beschreiben worden ist." Experiments on the synthesis of the acid were stated to be in progress but have not been reported.In the same year Erlenmeyer (2) wrote, "Wie im experimentellen Theile gezeigt werden wird, ist es