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The first oxidation produd of purine is hypoxanthine, which I 

 long been known as a constituent of meat extract. Adenine, the amino 

 derivative of hypoxanthine, occurs in combination with other subsl 

 in the nuclear material. The second oxidation product is xanthine and 

 its amino derivative, guanine. They occur in the same places .-is hypo- 

 santhine and adenine. The lii-jhest oxidation product of ;ill is the well- 

 known urinary constituent, uric acid, which may therefore 1"- chemically 

 designated ;is trioxypurine. In addition t<. the purines <<( animal origin. 

 there arc also certain outs of vegetable origin -the methyl purines, which 

 exist .-is tlic alkaloids of tea and coffee namely, caffeine, theobromine, 

 and theine. 



To understand the chemical structure of this group of Bubstanci 

 it is perhaps simplest to start with that of uric acid. This consists 

 3sentially of two urea molecules linked together by a central chain of 

 three carbon atoms, as will he evident from the accompanying structural 

 formula: 



This structure can he shown by methods both of decomposition and 

 of s\ nt he-is. When uric acid is decomposed by oxidizing it with nitric 



acid, it yields urea and a residue called alloxan; or it can he synthesized 

 from urea and trichlorlactamide, a derivative of lactic acid, which it 



will he remembered contains three carbon atoms. The changes invol 

 in this synthesis will he mad.' clear by examination of th< mpanying 



structural formula, in which the manner of production of the by- 

 products of the reaction (NH 8 , H a O and HC1 are show q by dotted In • - 



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