o>-AMINO-ACIDS 35 



S-Amino-n-valeric Acid, NH 2 . CH 2 . CH 2 . CH 2 . CH 2 . COOH. 



This, the first known example of a natural w-amino-acid, was ob- 

 tained by E. and H. Salkowski [1883] from putrefied fibrin and 

 muscle, and later by H. Salkowski [1898] from putrefied gelatin. 

 Ackermann [1907, 2] isolated it from putrid pancreas (and at first called 

 it putridine, because he failed to identify it). The substance was pre- 

 pared synthetically by Schotten [1884] by the oxidation of benzoyl- 

 piperidine with potassium permanganate. 



S-Amino-valeric acid is derived in putrefaction from both arginine 

 (ornithine) and proline. Ackermann [1910, 3] submitted 56 grm. of 

 arginine carbonate to putrefaction in the same way as aspartic acid 

 and glutamic acid (preceding sections), and obtained putrescine, 

 ornithine, S-amino-valeric acid (about 1 5 grm. of the aurichloride) but 

 not agmatine. The arginine is no doubt first broken down to ornithine, 

 and the latter by the first general process (p. 33) yields S-amino-valeric 

 acid. 



The putrefactive formation of S-amino-valeric acid from proline 

 (a-pyrrolidine carboxylic acid) has been observed more recently by 

 both Ackermann and Neuberg ; two hydrogen atoms are added and 

 the ring is opened. 



e-Amino-caproic Acid, NH 2 . (CH 2 ) 5 . COOH. 



This substance should be obtainable from lysine by putrefactive 

 deaminization ; an attempt to prove this was made by Ackermann 

 [1910, 3] with 98 grm. of lysine chloride. He obtained a large 

 quantity of cadaverine and a small quantity of a platinichloride fairly 

 readily soluble in alcohol and in water ; the analysis of this salt did 

 not agree with the composition required for the platinichloride of the 

 desired amino-caproic acid. 



/Mminazolyl-propionic Acid, 

 CH = C CH 2 .CH 2 .COOH 



N NH 



V 



CH 



This acid was first obtained from histidine by chemical means and 

 was also prepared synthetically by Knoop and Windaus [1906] (see 

 Plimmer's " Chemical Constitution of the Proteins," Part I, p. 1 26). Ac- 

 kermann [1910, i] then showed that it is also formed by putrefaction 

 from pure histidine hydrochloride ; the principal product was imin- 



3* 



