THE CHEMICAL CONSTITUTION OF THE UNITS 123 



Lysine. 



Lysine was discovered by E. Drechsel amongst the decomposition 

 products of caseinogen in 1889, and its presence in other proteins 

 gelatin, egg-albumin, conglutin, fibrin was shown by his pupils, Ernst 

 Fischer, Siegfried and Hedin. It was found by Kutscher in antipeptone 

 and by Kossel in the protamines. Its occurrence in germinating seed- 

 lings was demonstrated by Schulze and in vegetable proteins by Schulze 

 and Winterstein. Thus, like arginine and histidine it is a very widely 

 occurring constituent of the proteins. 



Drechsel gave it the formula C 6 H 14 N 2 O 2 and regarded it as a 

 diaminocaproic acid; Ellinger proved in 1899 that it possessed this 

 constitution, by obtaining cadaverine from it by putrefaction, which 

 showed that the two amino groups were in the a, e-positions : 



NH 2 . CH 2 . CH 2 . CH 2 . CH 2 . CH(NH 2 )COOH = 

 CO 2 + NH 2 . CH 2 . CH 2 . CH 2 . CH 2 . CH 2 . CH 2 . NH 2 . 



Henderson's experiments also showed that lysine must have this consti- 

 tution, namely a, e-diaminocaproic acid. Its constitution was only 

 definitely determined by synthesis by Fischer and Weigert by the 

 following method : 



When 7-cyanopropylmalonic ester is treated with nitrous acid, it 

 loses one of its carboxethyl groups and is converted into a-oximido- 

 S-cyanovalerianic acid, which on reduction with sodium amalgam yields 

 a, e-diaminocaproic acid, thus : 



/COOC 2 H 3 

 NC . CH 2 . CH 2 . CH 2 . CH<^ -> NC.CH 2 .CH 2 .CH 2 . C( = NOH) . COOC 2 H 6 -> 



X COOC 2 H 5 

 H 2 N . CH 2 . CH 2 . CH 2 . CH 2 . CHfNHa) . COOH 



Sorensen has also prepared lysine by the same method which he 

 employed for the synthesis of ornithine. 



Neither of these syntheses are very suitable for the preparation of 

 lysine. A good yield of lysine is more easily obtained by v. Braun's 

 method. Benzoylpiperidine is converted by the action of phosphorus 

 pentachloride into benzoylchloramylamine ; the chlorine atom is ex- 

 changed for the CN group which is hydrolysed to the COOH group. 

 The resulting e-benzoylaminocaproic acid is brominated with bromine 

 and phosphorus. Treatment with ammonia gives e-benzoylamino-a- 

 aminocaproic acid from which lysine is obtained by hydrolysis. The 

 reactions are : 



