Xanthine & Theobromine

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Xanthine:- : 

Xanthine:- Xanthine is a purine base found in most human body tissues and fluids and other organisms. A number of stimulants are derived from xanthine , including caffeine and theobromine.

j : 

j It occurs in tea extract and in animal tissues. It is a crystalline substance which decomposes at 150°C

Constitution:- : 

Constitution:- It is the parent compound of three important bases called caffiene, theobromine and theophylline. Its constitution is established as follows: When xanthine is oxidised with potassium chlorate in HCl solution, it forms alloxan and urea, indicating that xanthine has the uric acid skeleton because the latter also yields the same products on mild oxidation. Thus, on the basis of its relation with uric acid and its synthesis, the following structures were assigned to xanthine.

Synthesis:- : 

Synthesis:- Xanthine may be synthesised by the following three general methods: a) Fischer’s synthesis(1898):

Traube’s synthesis(1900): : 

Traube’s synthesis(1900):

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Bredereck’s synthesis(1959). Traube’s synthesis was modified by Bredereck’s et, al (1959)

Theobromine:- : 

Theobromine:- It derives its name from the greek word, thoes, meaning ‘god’ and broma meaning ‘food’. It is a white crystalline compound which melts at 157 °C It has a faintly bitter taste. It has slight solubility in water

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It occurs in cocoa beans up to the extent of 1.5 to 2.5 percent. However, it occurs in tea in trace amounts. In medicine, it is generally used as a diuetic in the form of its double compound with sodium salicylate under the trade name diurerin. It is also used as cardiac stimulant and remedy for dropsy.

Constitution:- : 

Constitution:- a) Molecular formula: This has been found to be C7H8O2H4 b) Presence of two methyl groups: When Herzig-Meyer’s method is applied to theobromine, it is found to contain two –NCH3 groups c) Oxidation: When theobromine is oxidised with potassium chlorate in HCl, it yields monomethyl alloxan and monomethyl urea, indicating that theobromine possesses the same skeleton as that of uric acid in which one of the methyl groups is present in pyrimidine ring while the other in imidazol ring

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d) Methylation: When the silver salt of theobromine is methylated, it yields caffiene(1,3,7-trimethylxanthine), revealing that the methyl group of imidazole ring is present at position 7 whereas the methyl group of pyrimidine ring may be present at position 1 or 3 and thus theobromine may be either (I) or (II) Out of two structures, the structure (II) has been found to be correct because theobromine could be synthesised from 3-methyluric acid as well as from 7-methyl uric acid but not from 1-methyluric acid. This fact clearly reveals that theobromine must be 3,7-dimethyl xanthine.

Synthesis:- : 

Synthesis:- Finally the structure of theobromine has been confirmed by its synthesis: a) Fischer’s synthesis:

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b) Traube’s synthesis:

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c) From xanthine( Bredereck, 1959):

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