118 AARON BENDICH 



methylene, and amino groups of the glycine arise, respectively, from carbons 

 4 and 5 and N-7 of the guanine.^"^ Upon treatment of guanine with con- 

 centrated sulfuric acid at "high temperature," carbons 2 + 6 are liberated 

 as CO2 and carbon 8 as CO.'^^ Both hypoxanthine and adenine yield glycine, 

 ammonia, carbon dioxide, and carbon monoxide (the latter probably from 

 the decomposition of formic acid) upon hydrolysis with concentrated HCl 

 at 180-200°^^* The amino group of the liberated glycine arises from N-7 

 of the adenine i^"^ the formation of 4-amino-5-imidazolecarboxamidine from 

 such a hydrolysis was mentioned above. The formic acid resulting from the 

 hydrolysis of adenine with 30 % sulfuric acid'^^ may be collected by steam 

 distillation. 



Data on the action of alkali on pyrimidines and purines are scanty. 

 Hypoxanthine is decomposed into ammonia and hydrocyanic acid upon 

 treatment with fused KOH at 200°;^" adenine and hypoxanthine are, how- 

 ever, unaffected by boiling in aqueous alkah.^^^-'" (At 200° in water alone, 

 hypoxanthine breaks down to CO 2 , NH3 , and formic acid.^") Pyrimidines 

 containing hydroxy or amino groups both at position 4 and 5 are unstable 

 in alkaline solution at room temperature; the instability is markedly in- 

 creased when, in addition, such a group occupies position 6.^^* 



Reference has already been made to the nitrous acid deamination of 

 adenine, guanine, cytosine, and 5-hydrox3Tnethylcj4osine to the cor- 

 responding hydroxy derivatives. Nitrous acid deaminates both 5-methyl- 

 cytosine and 5-methylisocytosine to thymine.'^" 2,6-Diaminopurine is de- 

 aminated to isoguanine (cf. DavolP^O but the latter resists the action of 

 nitrous acid.^''^ 8-Aza-adenine and -guanine are converted by nitrous acid 

 to the corresponding hypoxanthine and xanthine analogues.^*^ The amino 

 group at C2, 4, and 6 of the pyrimidine moieties of these various compounds 

 therefore do not exhibit the properties expected of typical aromatic amino 

 derivatives, and accordingly are analogous in chemical behavior to the a- 

 and 7-aminopyridines.^^^ On the other hand, a behavior approximating that 

 of aromatic amino compounds is shown by 5-aminopyrimidines (cf. Whit- 

 taker,^^^ Lythgoe,^^^ and Rose^^^). 



By the action of nitrous acid, a nitroso group can be introduced into the 

 5-position of certain pyrimidines. This reaction forms the basis of the 

 valuable Traube synthesis of purines (see below). Only those pyrimidines 

 can be nitrosated which contain amino or hydroxy groups in both positions 



334 W. H. Marsh, /. Biol. Chem. 190, 633 (1951). 



"5 M. Kriiger, Z. physiol. Chem. 16, 160 (1892); 18, 351, 423 (1894). 



336 C. D. Stevens, /. Biol. Chem. 120, 751 (1937). 



'" <''' A. Kossel, Z. physiol. Chem. 6, 422 (1882). 



(b) 12, 241 (1888). 

 338 F. L. Rose, /. Chem. Soc. 1952, 3448. 



