150 



SIDNEY W. FOX 



^ 9 w ^%v' <jsSf 



12 3 4 5 6 7 8 



Fig. 2. Tracing of chroma togram of products from ammonium hydrogen malate. 



(i) 10 /<!. of aspartic acid; (2) 10 ^1. of a-alanine; (3) 10 ^1. of ^-alanine; 

 (4) 10 ^1. each of aspartic acid and a-alanine; (5) 10 /tl. each of aspartic acid and 

 /5-alanine; (6) 10 ^mI. each of aspartic acid, a-alanine, and /3-alanine; (7) 20 /<!. of 

 product from ammonium malate heated at 160°; (8) 20 fil. of product from 

 ammonium malate heated at 200°. Chromatographic solvent was 7 pyridine : 3 

 water. Coloured with ninhydrin. 



GLUTAMIC ACID 



PEPTIDES 



9-AL/N!NE 



Fig. 3. Thermal pathways. 



The reactions for which detailed supporting data have been published are 

 depicted in Fig. 3 by soUd arrows. Other reactions are indicated with broken 

 arrows. 



The obtaining of conclusive evidence for the production of peptides by 

 thermal treatment of unsubstituted amino acids revealed some striking features. 

 Early reports on heating of amino acids show that these tend to form diketo- 

 piperazines, amines, tars and other decomposition products [9, 10] rather than 

 linear peptides. Even the product from aspartic acid, which appeared to be an 



