Uric acid preparation from purines

A 2- or 6-hydroxy-substituted purine can be prepared from the corresponding 4,5-diamino-pyrimidinol by cyclization with an acid, ester, ortho ester, or amide. If the ring closure is performed with reagents such as urea, alkyl chloroformates, urethanes, phosgene, and alkyl isocyanates, the 8-hydroxypurines are formed. Various xanthine and uric acid derivatives have been prepared by the condensation of 5,6-diaminopyrimidine-2,4-diols with formic acid. Purin-2-ol (1) was prepared by this route from 4,5-diaminopyrimidin-2-ol and ethyl orthoformate. ... 

Syntheses of adenine and guanine from uric acid illustrate well the selective transformations to which the halo-purines, prepared from a precursor oxy-purine, can be put. 

Purine a heterocyclic compound with a condensed pyrimidine-imidazole ring system. Af, 120.1, m.p. 217°C P. was prepared from uric acid by Emil Fischer in 1884. The free compound is not known to occur naturally, but the otherwise unsubstituted P. ring system is found in combination with libose in the nucleoside antibiotic, Nebularine (see). 

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