ALBUMINS OR PROTEINS. 



149 



pare at the same time the formation of ordinary leucine from iso-amyl- 

 alcohol: 



^ 3 >CH.CH 2 .CH 2 OH 



iso-amyl-alcohol 



+ O 

 1 - H 2 



3 >CH.CH 2 .CHO 



i iso-valeraldehyde 

 + HCN + NH 3 



u 



i d-amyl-alcohol 

 + 



~ XA f 



>0 



d-valeraldehyde 

 + HCN + NH 3 



* - H 2 O 



. CH 2 . CHNH 2 . CN 



iso-valero-amino-nitril 



+ 2H 2 O 



-NH 3 



C 2 3 >CH.CHNH 2 .CN 

 ^ 2 ri5 



I d-valero-amino-nitril 



+ 2H 2 O 

 * - NH 3 



>CH . CH 2 . CHNH 2 . COOH 

 a-amino-isobutyl-acetic acid 



= leucine 



[ 3 >CH.CHNH 2 .COOH 



a-amino-methyl-ethyl-propionic 

 acid 

 isoleucine 



Serine is closely related to alanine. It was isolated in 1865, by Cramer, 1 

 from silk glue (or sericin). It is an a-amino-/3-oxypropionic acid: 



CH 2 (OH). CH(NH 2 ). COOH.( 2 ). Serine as it occurs in nature is laevo- 

 * 



rotary. 3 



Of the di-basic amino acids only two are known: a-aspartic acid and 

 glutamic acid. The former is an a-amino-succinic acid. 



COOH 

 *CH(NH 2 ) 

 CH 2 

 COOH. 



1 E. Cramer: J. prakt. Chem. 96, 76 (1865). 



2 For the synthesis from ammonia, hydrocyanic acid, glycolaldehyde, cf. E. Fischer 

 and H. Leuchs: Sitzber. Akad. Wiss. Berlin, 1902, and Ber. 35, 3787 (1902). 



3 Emil Fischer: Ber. 40, 1501 (1907). 



