128 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



By treating the chloromethyl glyoxaline with ethyl sodiochloro- 

 malonate, ethyl glyoxaline chloromalonate was formed. This ester on 

 saponification lost carbon dioxide and gave glyoxaline chloropropionic 

 acid ; by treating this compound with ammonia the chlorine atom 

 was replaced by the NH 2 group and glyoxaline amino propionic acid, 

 or histidine was obtained : 



CH NH 



II 



C _ N 



CH 2 C1 



chloro- 



methyl 



glyoxaline. 



The racemic histidine, thus obtained, was resolved into its optically 

 active isomers by the fractional crystallisation of its salt with d-tartaric 

 acid. 



Glyoxaline-chloropropionic acid only differed from Windaus and 

 Vogt's compound and glyoxaline-oxypropionic acid, prepared by the 

 action of silver oxide, only differed from Frankel's oxydesamino- 

 histidine in their melting-points which is most probably due to the fact 

 that the compounds of Windaus and Vogt and of Frankel were pre- 

 pared from the natural 1-histidine. 



In connection with histidine, the work of Windaus and Knoop on 

 the formation of methylimidazole from glucose must be mentioned on 

 account of the possible synthesis in the animal body of both histidine 

 and purine bases. 



It has long been known that glucose is converted by alkalies into 

 lactic and other oxy acids. Knoop and Windaus investigated this 

 reaction in the presence of ammonia, in the form of the strongly dissoci- 

 ated zinc hydroxide ammonia. By exposing glucose and zinc hydrox- 

 ide ammonia to diffused daylight they obtained methylimidazole. 

 Inouye has also obtained this compound employing galactose and 

 arabinose instead of glucose. 



The formation of methylimidazole is explained as follows : 



From the sugar glyceric aldehyde is probably first formed, and this 

 is converted into methyl glyoxal by loss of water, from which lactic 

 acid may arise by the subsequent addition of water : 



CH 2 OH . CHOH . CHO -> CH 3 .CO.CHO - CH 3 . CHOH . COOH 



