54 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



Br 



CH 2 



CH 2 



COOH 

 Laevulinic acid 



= NOH 



CH 2 



COOH 



COOH 



Dibromolaevulinic Glyoxylpropionic 

 acid acid 



COOH 



Diisonitrosovalerianic 

 acid 



This is converted into furazanpropionic acid by sulphuric acid and then 

 into cyanonitrosobutyric acid by caustic soda. Saponification changes 

 the cyanonitrosobutyric acid into a-nitrosoglutaric acid from which 

 glutamic acid is obtained by reduction : 



COOH 



I 



CH . NH 

 H 2 | 

 -- > CH 2 



CH 2 



COOH 



o-Nitrosoglutaric Glutamic acid 

 acid 



This appears to be the only recorded synthesis of glutamic acid. 



The next member of this homologous series, a-amino-adipic acid, 

 has been prepared by Sorensen from phthalimidosodium malonic ester 

 and chlorobutyronitrile in the following way : 



COOC 2 H 5 



l/ Na 



CO, 

 CO' 



. CH . CH . CH 2 CN = 



COOC 2 H 5 

 | X CH 2 .CH 2 .CH 2 CN 



COOC 2 H 

 COOC 2 H 5 



b/ 2 ,CO 



> 



^co/ 



NaCl 



COONa 



, 



\ 



COOC 2 H 5 



. CH. CH. COONa 



C 6 H 4 



+ 4 NaOH+H 2 = C< + 2 C 2 H 5 OH + NH 3 



\NH. CO. C 6 H 4 . COONa 



COOC 2 H 5 



COONa 



I /CH 2 . CH 2 . CH 2 . COONa 

 C( 



I \NH . COC 6 H 4 COONa 

 COONa 



COONa 



CH 2 . CH 2 . CH 2 COOH 



4 HC1 



H.C.NH 2 

 COOH 



C 6 H 4 (COOH) 2 + CO 2 + 4 NaCl 



Sorensen suggests that the same reactions might be employed for 

 the synthesis of aspartic acid and of glutamic acid, in the case of the 

 former condensing the sodium phthalimidomalonic ester with chlor- 

 acetic ester and in that of the latter with /3-chloropropionic ester 



