90 AARON BENDICH 



(including tubercle bacilli) or viral sources/^ and has not been found in the 

 pentosenucleic acids. A nucleotides^ and nucleosides^ of 5-methylcytosine 

 have been isolated from the DNA of thymus and wheat germ, respectively. 

 An excellent discussion concerning this pyrimidine is available .^^ 



Quite recently, the absence of cytosine in the DNA of coliphage T2 was 

 reported.ss Since hydrolysis of the DNA with 70% HCIO4 (100°), which 

 was employed," does not lead to a destruction of cytosine (see also Wyatt^^), 

 and since other analyses^^ ^9 indicated its apparent presence in T2 and Te , 

 a reinvestigation was made by Wyatt and Cohen. ^^ Of great interest was 

 their discovery of the occurrence in the DNA's of T-even bacteriophages 

 (but not in the DNA's of thymus or of the host E. coli) of a new pyrimidine 

 base, 5-hydroxymethylcytosine (XV) in place of cytosine. The base XV, 

 which withstands the hydrolysis with 88% formic acid (175° for 30 min.) 

 necessary for its liberation from the DNA's, but which is largely destroyed 

 by the treatment with HCIO4, has spectral and chromatographic proper- 

 ties (Rf value in isopropanol-water-HCl)^^ very similar to those of cytosine 

 (and 5-methylcytosine). These considerations serve to explain the above- 

 mentioned apparent discrepancies.s6S8,79 a synthesis of the new base (un- 

 published), its nitrous acid deamination to a uracil-like derivative, and 

 the isolation of a nucleotide have been reported. ^^•*'' 



Because of the importance of this new base (XV) in DNA, and its struc- 

 tural similarity to vitamins Bi (thiamine, XVI) and Be (pyridoxine, XVII), 

 a more detailed discussion of the chemistry of hydroxymethylpyrimidines 

 and related compounds is given. 



In an attempt to prepare A'^-methyluracil derivatives, Kircher*^ condensed 4-methyl- 

 uracil (XVIII)''^ with formaldehyde in either dilute acid or alkaline aqueous solution 

 and obtained 4-methyl-5-hydroxymethyluracil (XIX) in high yield. Proof of its struc- 

 ture was readily obtained upon its reduction to the known 4 , 5-dimethyluracil (XX) .^* • ^^ 

 The compound XIX was unexpectedly labile to hydrolysis, undergoing a carbon-carbon 

 cleavage upon mere boiling with water, and the original 4-methyluracil (XVIII) and 

 formaldehyde were regenerated by this mild treatment. Other, ill-defined, products 

 (C11H12N4O4 and C12H14N4O5) resulted when XIX was subjected to hot mineral acid 

 (cf. Endicott and Johnson''-*^ for a description of similar substances made by treating 



" G. R. Wyatt, J. Gen. Physiol. 36, 201 (1952). 



''^W.E.Cohn, J. Am. Chem. Soc. 72, 2811 (1950); 73, 1539 (1951). 



'* C. A. Dekker and D. T. Elmore, /. Chem. Soc. 1951, 2864. 



" G. R. Wyatt, Exptl. Cell Research 3, Suppl. 2, 201 (1952). 



" A. Marshak, Proc. Natl. Acad. Sci. U. S. 37, 299 (1951). 



" A. Marshak and H. J. Vogel, /. Biol. Chem. 189, 597 (1951). 



" J. D. Smith and G. R. Wyatt, Biochem. J. 49, 144 (1951). 



" L. L. Weed and S. S. Cohen, /. Biol. Chem. 192, 693 (1951). 



8" G. R. Wyatt and S. S. Cohen, Ann. inst. Pasteur 84, 143 (1953). 



8' W. Kircher, Ann. 385, 293 (1911). 



»2J. Schlenker, Ber. 34, 2812 (1901). 



83 M. M. Endicott and T. B. Johnson, J. Am. Chem. Soc. 63, 1286 (1941). 



" M. M. Endicott and T. B. Johnson, J. Am. Chem. Soc. 63, 2063 (1941). 



