204 ABIOGENIC ORGANIC-CHEMICAL EVOLUTION 



intermediate compound in this reaction is /5-hydroxyacrylic 

 acid which is formed from the malic acid 



NH» COOH NH — CO 



II 11^ 



CO + CH -> OC CH + 2H2O 



I II I 11 



NHg HCOH HN — CH 



urea j8-hydroxyacryHc acid uracil 



Uric acid can be synthesised by the method of R. Behrend 

 and O. Roosen^^^ from urea and mesoxalic acid: 



NH, COOH CO — NH CO ^NH NH — CO NH2 



II II 1 I I I I 



CO + CO -> CO CO + Ho ^ HCOH CO -> CO COH + CO 



II II I I 1 II I 



NH2 COOH CO — NH CO NH NH— COH NH2 



ureamesox- alloxan dialuricacid isodialuric acid 



alic acid 



NH CO 



I I 



-> CO C— NH+ 2H2O 



>CO 



NH — C — NH 



uric acid 



Under reducing conditions, uric acid may be converted 

 to various purine bases/^' In connection with the possibility 

 of the primary formation of nitrogen-containing heterocyclic 

 compounds the work of H. Staudinger and K. Wagner"^ on 

 the products of the condensation of urea with formaldehyde 

 is very interesting. 



Recent work using marked atoms has shown, however, 

 that the synthesis of purines and pyrimidines in the living 

 organism occurs in a different way.^°° It is not based on 

 urea^" as was thought earlier, but proceeds by the combina- 

 tion of formyl residues with ammonia and oxaloacetic acid 

 or with glycine. ^"^ 



