Synthesis of Nucleosides and Nucleotides- • 167 



and Dr. Davoll has been investigating the possibiUties of 

 practical syntheses of some of the desired compounds. The 

 pubhshed routes (Davoll, Lythgoe and Todd, 1948) for the 

 synthesis of adenosine and guanosine are via uric acid, and 

 they can be expected to result in over-all yields from inorganic 

 carbon of about 2 • 5 and • 5 per cent, respectively. For this 

 reason it was deemed desirable to study possible direct 

 syntheses from the parent purines. Briefly this study has 

 culminated in the use of the chloromercuri derivatives of 

 acyl-substituted aminopurines and acetochloro-D-ribofuranose 

 (Davoll and Lowy, 1951). By this method adenosine has 

 been obtained in a yield of 20 per cent from adenine. 



The application of this procedure to 2,6-diacetamidopurine 

 has resulted in a synthesis of 2,6-diamino-9-j3-D-ribofuranosyl- 

 purine, the nucleoside which corresponds in configuration to 

 natural adenosine. This nucleoside could be partially 

 deaminated by the action of nitrous acid, in analogy to the 

 chemical behaviour of 2,6-diaminopurine, to yield 6-amino-2- 

 hydroxy-9-/8-D-ribofuranosylpurine, or crotonoside. It has 

 also proven possible to preferentially deacetylate the sugar 

 and the 6-amino group of pentacetyl-2,6-diamino-9-/8-D- 

 ribofuranosylpurine and, by subsequent treatment with 

 nitrous acid and further deacetylation, to obtain guanosine. 



Metabolic Studies 



The initial studies with labelled materials larger than the 

 purines or pyrimidines involved the feeding of the intact 

 ^^N-labelled yeast nucleic acid. The mixture of mono- 

 nucleotides derived from it was also administered by intra- 

 peritoneal injection (Roll, Brown, DiCarlo and Schultz, 1949). 

 There was essentially no incorporation of the purines of the 

 orally administered nucleic acid into the tissue polynucleo- 

 tides, and although there was a definite incorporation of the 

 purines of the intraperitoneally administered mixture of 

 nucleotides, it was obvious that these were much less effective- 

 ly utilized than was free adenine. It was significant that 

 either the intact nucleic acid or the mixture of nucleotides 



