AARON BENDICH 



condensed in alkaline solution at room temperature to afford 2-ethylmer- 

 capto-6-hydroxypyrimidine. The hydroxyl group was replaced (phosphorus 

 pentachloride) by chlorine, which in turn was replaced by an amino group 

 upon treatment with alcoholic ammonia. The ethylmercapto group was 

 replaced by hydroxyl upon hydrolysis (125°) with hydrobromic acid. It 

 was found ^' that the synthetic cytosine and that obtained from wheat 

 germ and spleen nucleic acids were identical. With the exception, recently 

 reported, of the DNA of T- even-numbered bacteriophages of E. coli,^^ all 

 specimens of PNA and DNA in which the pyrimidines have been charac- 

 terized have been found to contain cytosine. 



OH 



NH., 



OH 



CH3 



N 



An/ 



N 



An- 



HO 



N 



/ 



NH., 



N 

 I , 



NHo 



CH3 



CH2OH 



N 



An/ 



HO HO HO HO 



XI XII XIII XIV XV 



Thymine Cytosine Uracil 5-Methylcytosine 5-Hydroxymethyl- 



Pyrimidines occurring in the nucleic acids 



cvtosine 



Following a procedure for the isolation of thymine from herring sperm, ^^ 

 Ascoli^® isolated from yeast nucleic acid (1900-1901) a new compound 

 (C4H4N2O2) which, as he pointed out, corresponded in empirical composi- 

 tion to the previously postulated (cf. Behrend^^) vracil (XIII)." This sur- 

 mise was confirmed by the following synthesis of uracil by Fischer and 

 Roeder,^* who considered their product to be identical wdth the natural 

 substance : 



" W. L. Wheeler and T. B. Johnson, Am. Chem. J. 29, 505 (1903). 



