32 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



a-8-Dibromovaleryl-chlonde for the introduction of the prolyl radicle. 

 Fumaryl -chloride for the introduction of the asparagyl radicle. 



In order to introduce the asparagyl group into an amino acid, chloro-succinyl chloride, 

 the corresponding halogen-acyl chloride, cannot be employed, since on treatment with am- 

 monia it yields fumaryl derivatives. These, however, when heated with strong ammonia 

 again take up ammonia forming the asparagyl compound, and hence can be employed for 

 this purpose. 



lodoacetyl - chloride and iodopropionyl-chloride were used by Abderhalden and 

 Guggenheim to prepare glycyl-3, 5 - diiodo-1-tyrosine and alanine-3, 5 -diiodo-1-tyrosine. 

 Abderhalden and Baumann employed them for combination with tryptophane ; these pro- 

 ducts were not obtained in a crystalline state. 



The introduction of the prolyl group into an amino acid by means 

 of a-S-dibromovaleric acid chloride reminds us of the synthesis of pro- 

 line, in which when the compound is treated with ammonia in order to 

 exchange the Br atoms for NH 2 , ammonia is lost and ring formation 

 occurs. Prolyl-alanine is prepared as follows : 



CHjBr . CH, . CH, . CHBr . COC1 + NH, . CH(CHj) . COOH 



= HC1 + CH,Br . CH, . CH a . CHBr . CO NH . CH(CH S )COOH 



CH,Br . CH, . CH, . CHBr . CO NH . CH(CHj) . COOH + 3 NH, 



=2NH 4 Br + CH, . CH, . CH, . CH . CO NH . CH(CHj)COOH 



IH 



These radicles can be introduced into all the simple mono-amino 

 acids, such as alanine, leucine, tyrosine, etc. ; also into cystine and the 

 dicarboxylic acids when the compounds such as dialanyl-cystine and 

 asparagyl-dialanine are formed. Abderhalden, in conjunction with 

 Guggenheim and Hirszowski, has prepared dipeptides of diiodotyrosine. 

 These can also be prepared by the action of iodine on the correspond- 

 ing polypeptide containing tyrosine. 



Glycyl-amino-acetal was obtained by E. Fischer in 1908 by com- 

 bining chloracetyl chloride with aminoacetal and subsequent treat- 

 ment with ammonia. Hydrolysis of the compound by acid gave a 

 product which was most probably glycylaminoaldehyde, i.e., the al- 

 dehyde of glycyl-glycine. The combination has also been effected 

 with higher amino acids and -amino acids. 



The halogen acyl radicle when combined with proline does not 

 yield the dipeptide on treatment with ammonia. The compound which 

 is formed is apparently the amide of the hydroxy acid, e.g., oxyiso- 

 capronyl-proline amide : 



S Vf slia 



(CH.), . CH . CH, . CH CO N< 



\CH-CH, 

 OH 



CO.NH, 



