AMINO ACIDS , PEPTIDES AND PROTEINS 



TABLE 3. STRUCTURE OF HETEROCYCLIC AMINO ACIDS 



213 



ca 



CH. 



CH-CO^H 



I "^ 



NH 



H« C CH-CO«H 



H 



azetidine-2-carboxylic acid 



pipecolic acid 



CH. 



CH CH, 



I 



I 



H«C CH-CO^H 



N 

 H 



CH 



^ \ 

 HC CH 



I I "^ 



H^C CHCOoH 



N 

 H 



4-methyl proline 



baikiain 



HC N — 



CHpCHCOpH 

 NH^ 



HC N 



C'^ 

 H 







HO^C 



CH^CHCO^H 



H. 



beta pyrazol-1-ylalanine 



stizolobic acid 



