THE CHEMICAL CONSTITUTION OF THE UNITS 113 



tained aspartic acid from acid ammonium fumarate and maleate. At 

 Liebig's suggestion these reactions were confirmed by Wolff. It was 

 shown by Engel, in 1887, that aspartic acid could be obtained directly 

 by heating maleic or fumaric acid with 'alcoholic ammonia to 140-150 

 without the formation of the intermediate substance which is fumari- 

 mide, and to which the following constitutional formulae have been 

 given : 



C0\ CO N CO 



CH-N CH/ CH 2 



CH 2 CH 



CH 2 / 



co/ 



These syntheses give no indication as to the structure of aspartic 

 acid, the constitutional formula of which is based upon Kolbe's work, 

 that it is amino-succinic acid ; the only synthesis of aspartic acid which 

 confirms this constitution appears to be that by Piutti in 1 887. Sodium 

 oxalacetic ester, prepared from oxalic ester and acetic ester in the 

 presence of sodium ethylate : 



COOC 2 H 5 COOC 2 H 6 



COOC 2 H e CO 



+ NaOC 2 H 6 = 2C 2 H 5 OH + [ 

 CH 3 CHNa 



COOC 2 H C COOC 2 H 5 



gives an oxime when treated with hydroxylamine hydrochloride : 



COOC 2 H S COOC 2 H 8 



CO C = NOH 



+ H 2 NOH = | + NaCl + H 2 O 



CHNa CH 2 



COOC 2 H B COOC 2 H 5 



and this is reduced by sodium amalgam to sodium aspartate : 

 COOC 2 H B COONa 



C = NOH CHNH 2 



+ 4 H + 2 NaOH = | + 2C 2 H 5 OH + H 2 O 



CH 2 CH 2 



COOC 2 H 5 COONa 



From this oxime Piutti has also prepared the two isomeric aspara- 

 gines : 



PT, I. 



