88 THE PROTEIN SUBSTANCES. 



by TREAT B. JOHNSON. 1 He has prepared the following: thioglycylglycin- 

 thioamide NH 2 CH 2 CS.NHCH2CSNH2 which is analogous to glycylgly- 

 cinamide, NH2CH2CO.NHCH2CONH2 and also dithiopiperazine 



CH 2 .CS X 



HN/ >NH. 



X CS.CH 2 



Polypeptides of higher amino-fatty acids such as a-aminolauryla- 

 lanine, a-aminolaurylleucine and others have been prepared by HOP- 

 WOOD and WEiZMANN. 2 These peptids are different from the so-called 

 lipopeptids prepared by BONDI and his collaborators 3 which are not 

 chains of only amino-acids but combinations between a high fatty acid, 

 such as lauric- or palmitic acid and an amino-acid (glycocoll or alanine) 

 or a dipeptide (lauryl-alanylglycine) . 



Methylated polypeptides such as methyl- and dimethylleucylglycine (E. 

 FISCHER and GLUUD) and betaindiglycylglycine 



(CH 3 ) 2 N. CH 2 CO.NHCH 2 CO.NHCH 2 CO 



(ABDERHALDEN and KAUTZSCH) are also known. 4 Amides of amino-acids and 

 dipeptides have been prepared by BERGELL 6 and his co-workers. 



The methods used by E. FISCHER in the synthetical preparation of 

 polypeptides are chiefly as follows: 



The first dipeptide prepared by him, glycylglycine, he obtained from glycocoll 

 ethyl ester which in water is transformed into a diketopiperazine, glycine anhy- 

 dride, according to the following equation: 



/CH 2 .C(X 



2(NH 2 CH 2 CO.O.C 2 H 5 ) = 2C 2 H 5 OH+NH< >NH. 



X CO.CH/ 



By the action of dilute alkali upon this anhydride with the taking up of water the 

 glycylglycine NH 2 CH 2 CO.NHCH 2 COOH is formed, and according to this prin- 

 ciple other dipeptides can also be prepared. 



Another method which has much greater application consists in the anchoring 

 of an amino-acid to a halogen of an acid radical, for example, by the action of 

 brompropionyl bromide or chloride upon glycocoll according to the following 

 equation: 



CH 3 CHBrCOCl+NH 2 CH 2 COOH=HCl+CH3CHBrCO.NHCH 2 COOH 



1 Journ. of biol. Chem., 9. 



2 See Chem. Centralbl., 1911. 



3 Bioch. Zeitschr., 17 and 23; see also Abderhalden and C. Funk, Zeitschr. f. physiol. 

 Chem., 65. 



4 Fischer and Gluud, Annal. d. Chem. u. Pharm., 369; Abderhalden and Kautzsch, 

 Zeitschr. f. physiol. Chem., 72 and 75. 



Ibid., 64, 65 and 67. 



