BASES DERIVED FROM THE PROTEINS 237 



Pyman {ibid. 191 1, 99, 668). Diaminoacetone (obtained from 

 citric acid) (I.) is heated with one molecular proportion of 

 potassium thiocyanate, according to Gabriel's method ; on 

 oxidising the mercaptan (II.) thus produced with nitric acid, 

 the nitrous acid which is formed attacks the amino-group and 

 the thio-amino compound is converted into hydroxymethyl- 

 glyoxaline (III.) : 



I. II. III. 



CH 2 .NH 2 CH.NH\ CH.NHv 

 I KCNS || >C.SH || J>CH 



CO -» C N^ -> C N^ 



I I I 



CH 2 .NH 2 CH 2 .NH 2 CH 2 . OH 



The hydrochloride of the last-named base may be converted by 

 means of phosphorus pentachloride into chloromethylglyoxaline, 

 a compound which is related to glyoxaline in the same way 

 that benzylchloride is to benzene and is therefore a valuable 

 material for syntheses of glyoxaline derivatives. On converting 



the chloride (IV) into the corresponding cyanide (V) and 

 reducing this latter, the desired aminoethylglyoxaline (iminazo- 

 lylethylamine) (VI) is obtained. 



Not only has Pyman been able in this way to obtain the 

 latter base in considerable quantity but by a modification of 

 the method outlined above he has also succeeded in synthesising 

 histidine itself. The synthesis of this important amino-acid had 

 hitherto baffled a number of chemists. 



It is probable that small quantities of iminazolylethylamine 

 are somewhat widely distributed in nature. The base has 

 been found in (fermented) Soya beans by Kiyohisa Yoshimura 

 (Biochem. Zeitsch. 19 10, 28, 16) and in the mucous membrane 

 of the small intestine of the ox by Barger and Dale. It is most 

 likely therefore the depressor substance in the secretin of 

 Bayliss and Starling, with which its physiological action and 

 solubilities agree. Small quantities apparently are also present 

 in commercial extracts of meat. In these cases, iminazolyl- 

 ethylamine is produced by bacterial action but there are certain 



