14 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



except that benzoic acid appears in the place of hippuric acid. Hip- 

 puryl aspartic acid azide and aniline give a compound which is half 

 anilide and half carbanilide, and this on hydrolysis is converted into 

 a-/?-diaminopropionic acid, hippuric acid, aniline and carbonic acid : 



C 6 H 5 .CO.NH.CH 2 .CO NH.CH.CO NH.C 6 H 5 



I + 3H 2 = 



CH,.NH.CO.NH.C 6 H 5 

 C 6 H 5 . CO . NH . CH 2 . COOH + NH 2 . CH, COOH 



| + 2 C 6 H 5 .NH 2 +C0 2 



CH 2 .NH 2 



The normal urethane formed by the action of alcohol on hippuryl 

 aspartic acid azide, yields on hydrolysis hippuric acid, carbonic acid, 

 alcohol and aminoacetaldehyde : 



C 6 H 5 . CO . NH . CH, . CO NH . CH . NH . COOC 2 H 5 



I 



CH 2 .NH.COOC 2 H 5 

 C 6 H 5 . CO . NH . CH 2 . COOH + 2 NH 3 + NH 2 . CH 2 . CHO + CO 2 + 2C 2 H 5 OH 



The first reaction shows the conversion of a compound belonging to 

 the series of dibasic monoamino acids into a diaminomonocarboxylic 

 acid ; in the second reaction, a dibasic amino acid is changed into the 

 aldehyde of the monobasic glycine. 



Finally, propylenediamine was obtained when the urethane, resulting 

 from the action of alcohol upon hippuryl-/3-aminobutyric acid azide, was 

 hydrolysed : 



C 6 H 6 . CO . NH . CH 2 . CO NH . CH(CH,) . CH 2 . NH. COOC 2 H 5 2 

 C 6 H 5 . COOH + NH 2 .CH 2 . COOH + NH 2 .CH(CH 3 ).CH a .NH 2 +CO 2 + C 2 H 5 



which shows the conversion of an amino acid derivative into a diacid 

 base. 



These transformations of amino acid derivatives increases our in- 

 terest in these compounds prepared by Curtius and his pupils, and gives 

 an impulse to their further study, especially as formaldehyde is such an 

 important compound in the synthesis of sugars by plants, and as the 

 diamino acids and diamines occur as products of decomposition of pro- 

 teins by enzymes and bacteria, although according to our present know- 

 ledge they are not formed in nature in this manner. 



These compounds have, however, given us an insight into complex 

 glycine, alanine and aspartic acid derivatives. E. Fischer has prepared 

 by his methods (see under polypeptides) compounds containing these 

 amino acids without the presence of the benzoyl group which is strange 

 to the protein molecule, but at present the aspartic acid compounds, if we 

 disregard Schiffs polyaspartic acid, which probably has another consti- 

 tution than that represented, are the most complex substances known 

 containing this important constituent of the protein molecule. 



