790 PHYSIOLOGY OF DIGESTION AND SECRETION. 



6. Leucin (a-amino-isobutylpropionic acid) : 



CHsx 



>CHCH2CHNH2COOH. 

 CH3/ 



Two other isomeric forms of this compound have been obtained from the 

 spht products, namely: 



Isoleucin (methyl-ethyl a-aminopropionic acid) : 

 CHav 



>CHCHNH2C00H. 

 CJi/ 



Normal leucin — norleucin (a-aminocaproic acid) : 

 CH3CH2CH2CH2CHNH2COOH. 



7. Aspartic acid (aminosuccinic acid) : 



COOHCHNH2CH2COOH. 



8. Glutamic acid: 



COOHCHNH2CH2CH2COOH. 



9. /3-Hydroxyglutamic acid: 



COOHCHNH2CHOHCH2COOH. 



10. Lysin (a-e-diaminocaproic acid) : 



CH2NH2CH2CH2CH2CHNH2COOH. 



11. Arginin (guanidin n-aminovalerianic acid) : 



/NH2 

 C=NH 

 \NHCH2CH2CH2CHNH2COOH. 



II. Amino-acids Containing a Benzene (Homocyclic) or a Hetero- 

 cyclic Nucleus. 



These compounds may be regarded as a-aminopropionic acids in which a 

 hydrogen attached to the /3-carbon atom is substituted by a benzene, an indol, 

 or an imidazol group. 



1. Phenylalanin (a-amino-/3-phenylpropionic acid): 



C6H6CH2CHNH2COOH, or 

 H 



^^\ 

 HC CH 

 * I II 



HC CH 



% / 



C . CH2CHNH2COOH. 



2. Tyrosin (o-amino-;8-para-oxyphenylpropionic acid) : 



C6H4OHCH2CHNH2COOH, or 

 OH 



HC CH 



I II 



HC CH 

 % / 

 C . CH2CHNH2COOH. 



