94 SCIENCE PROGRESS 



acid prepared by synthesis before Fischer commenced his re- 

 searches was diaminopropionic acid, which was obtained by 

 Klebs in 1894 by the action of ammonia on dibrompropionic acid. 

 The similar reaction with a-S-dibromvalerianic acid did not lead 

 to the synthesis of the expected diamino acid, but to the forma- 

 tion of a-pyrrolidine carboxylic acid (Willstatter, 1900). 



By making use of Gabriel's phthalimide method for synthesis 

 with a slight modification Fischer prepared a-8-diaminovalerianic 

 acid. The series of reactions occurring in the process are as 

 follows : 



C 6 HXco> NK + Br - CHi - CHi - CH2Br + Na - CH< ^COOc!H 5 

 = NaBr + KBr + C 6 H 4 <£°> N . CH : . CH 2 . CH 2 . CH<^oc*h' 



Bromination then gives 



C 6 H,<^> N . CH, . CH, . CH, . C <-Br 



CU \COOCH5 



which, on hydrolysis and loss of carbon dioxide on heating, 

 passes into phthalimidobromvalerianic acid : 



QH 4 <rn> N • CH - • CH - • CH., . C<- Br 



^ u \COOH 



This acid, on treatment with ammonia, whereby Br is exchanged 

 for NH 2 , and subsequent hydrolysis, yields a-S-diamino valerianic 

 acid : 



C 6 H 4 <£§QH + HiN • CH -' • CH * ' CH > • CH(NH,). COOH 



The benzoyl derivative of this diamino acid only differed 

 from Jaffe's ornithuric acid in optical activity; unfortunately, 

 owing to lack of material, the separation of ornithine, as this 

 diamino acid is called, into its stereoisomerides could not be 

 carried out. Sorensen, however, some years later was able 

 to accomplish this, and thus the synthesis of natural ornithine 

 was completed. Ornithine is a product of the hydrolysis of 

 arginine together with urea, and arginine was synthesised by 

 Schulze and Winterstein in 1899 by the addition of cyanamide 

 to ornithine. 



By the above series of reactions Fischer prepared a.-7-di- 

 aminobutyric acid, and the same reactions would lead to the 

 synthesis of lysine, which Fischer and Weigert obtained by a 

 simpler and better method, consisting of the following reactions : 



