CONDENSATION PRODUCTS OF AMINO ACIDS 



Anhydrides of Phenylglycine and Phenylalanine. The products 

 obtained by heating phenylglycine in an open vessel to the tempera- 

 ture of 140-1 50 C. were examined by P. J. Meyer in 1877. An an- 

 hydride of the formula : 



CH, \ CH, N(C 6 H ) CO 



) N(C 6 H B ) or I 



CO / CO N(C,Hj) CH, 



was isolated by crystallisation of the crude mass from alcohol and the 

 presence of an intermediate compound was suspected. 



Phenyllactimide was prepared, in 1883, by Erlenmeyer and Lipp 

 by the dry distillation of phenylalanine. This compound had pro- 

 perties analogous to leucinimide and lactimide. 



Anhydride of Sarcosine. The effect of heat upon an amino acid 

 and the exact composition of the resultant product was most carefully 

 studied by Mylius, in 1884, in the case of sarcosine (methylglycine). 

 Sarcosine was found to melt at 2 1 0-2 1 5 C. ; it became quite liquid at 

 220 C. Water, carbon dioxide and a volatile base (dimethylamine) 

 were evolved, and an oil remained. On distilling the oil a crystalline 

 mass resulted which was recrystallised from alcohol. Analysis and 

 molecular weight determinations showed that the substance had the 

 formula C 6 H 10 N 2 O a : on oxidation it gave dimethyloxamide and oxalic 

 acid. It was therefore represented by the structural formula : 



CH,.N CH, CO 



CO CH, N . CH, 



Mylius did not point out the resemblance of his substance to the other 

 anhydrides, and he consequently failed to clear up the nature of the 

 class of amino acid anhydrides. Their structure was only verified by 

 the later work of E. Fischer. 



