THE SYNTHESIS OF THE PROTEINS 13 



If, however, glycine were used instead of urea for combination with 

 the azide of phenylcarbamic acid phenylcarbaminoglycine resulted, 

 which was identical with the compound prepared by Paal in 1894 from 

 phenylisocyanate and glycine. 



With this compound Curtius and Lenhard continued the lengthen- 

 ing of the chain by the azide reaction, and obtained 



Phenylcarbaminoglycyl-glycine, C 6 H 5 . NH . CO NH . CH 2 . CO NH . CH, . COOH, and 

 phenylcarbaminodiglycyl-glycine, C 6 H 5 . NH . CO NH . CH 2 . CO NH . CH 2 . CO 

 NH.CH 2 .COOH. 



These compounds and their various derivatives prepared by Curtius 

 and his pupils are white crystalline compounds, for|the most part soluble 

 with difficulty in cold water. Some of them give the biuret reaction, 

 but others do not, in particular the less complex compounds where the 

 influence of the acid radical inhibits the reaction, although the com- 

 pounds possess the exact conditions, as determined by Schiff, for the 

 positive exhibition of the reaction. 



The reactions given by the azides with alcohol, ammonia, aniline, 

 etc., are of greater interest and may therefore be briefly summarised. 



By the action of ammonia the acid azides are either completely 

 saponified into the corresponding acids, or by a rearrangement in the 

 molecule, they are converted into derivatives of urea. With the dibasic 

 acids both possibilities may occur at the same time, and the resulting 

 compound is half acid amide and half urethane. Subsequent hydrolysis 

 clearly shows the nature of the component amino acid chain. Thus, 

 hippuryl urethane is formed from hippurazide and alcohol, 



C 6 H 5 . CO . NH . CH 2 . CO . N 3 + C 2 H 5 OH = C 6 H 5 . CO . NH . CH 2 . NH . COOC 2 H 5 + N 2 , 



and on hydrolysis it is converted into benzoic acid, ammonia, carbonic 

 acid and formaldehyde : 



C 6 H 5 . CO . NH . CH . NH. COOC 2 H 5 + 3 H 2 O = C 6 H 5 . COOH + 2NH 3 + HCHO + 



CO 2 + C 2 H 5 OH. 



The reaction therefore leads to the formation of formaldehyde from 

 glycine. Hippuryl alanineazide and aniline give the following urea 

 derivative : 



C 6 H 5 . CO . NH . CH 2 . CO NH . CH(CH 3 ) . CO NH . C 6 H 5 , 



which, on hydrolysis, breaks down into hippuric acid, ammonia, acet- 

 aldehyde, carbonic acid and aniline : 



C 6 H 5 .CO.NH.CH 2 .CO NH . CH(CH 3 ) . CO NH. C 6 H 5 + 3 H 2 O = 

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



The same products are obtained when the urethane derivative, ob- 

 tained from benzoylalanine azide and alcohol, is hydrolysed : 



C 6 H 5 . CO.NH . CH. (CH 3 ) . NH. COOC 2 H 5 + 3H 2 O = C 6 H 5 . COOH + 2 NH 3 

 CH 3 CHO + CO 2 + C 2 H 5 OH, 



