13.7- Trimethyl xanthine

Xanthine, 8-phenyl-synthesis, S, 588 Xanthine, 1,3,8,9-tetramethyl-synthesis, S, 588 Xanthine, 2-thio-dethiation, S, 558 Xanthine, 6-thio-synthesis, S, 588 Xanthine, 1,3,8-trimethyl-synthesis, 3, 308 S, 575 Xanthine, 1,3,9-trimethyl-structure, S, 509 Xanthine, 2,3,8-trimethyl-synthesis, S, 574... 

The trimethylated xanthine, caffeine, sublimes at 1800°C, which is a lower temperature of sublimation than theobromine.10 Temperatures of melting and sublimation are given in Table 1. 

Caffeine (3,7-dihyro-l,3,7-trimethyl-lH-purine-2,6-dione) is a natural product from tea, coffee, and other plants, and is present in many beverages and food. It is primarily metabolized in the liver by cytochrome P450 enzymes to give M-demethylated xanthine and few other metabolites (Fig. 2) [2,48 - 50]. About 17 caffeine metabolites have been identified in humans [51]. 

Caffeine Caffeine [l,3,7-trimethyl-l//-purine-2,6(3/7,7//)-dione], molecular formula C8H10N4O2, is a xanthine (purine) alkaloid, found mainly in tea leaves Camellia sinensis) and coffee beans (Coffea arabica). Caffeine is sometimes called guaranine when found in guarana (Paullinia cupana), mateine when found in mate (Ilex paraguariensis) and theine when found in tea. Caffeine is found in a number of other plants, where it acts as a natural pesticide. It is odourless white needles or powder. Apart from its presence in the tea and coffee that we drink regularly, caffeine is also an ingredient of a number of soft drinks. 

As indicated in Fig. 25-18, free adenine released from catabolism of nucleic acids can be deaminated hydrolytically to hypoxanthine, and guanine can be deaminated to xanthine.328 The molybdenum-containing xanthine oxidase (Chapter 16) oxidizes hypoxanthine to xanthine and the latter on to uric acid. Some Clostridia convert purine or hypoxanthine to xanthine by the action of a selenium-containing purine hydroxylase.3283 Another reaction of xanthine occurring in some plants is conversion to the trimethylated derivative caffeine. 328b One of the physiological effects of caffeine in animals is inhibition of pyrimidine synthesis.329 However, the effect most sought by coffee drinkers may be an increase in blood pressure caused by occupancy of adenosine receptors by caffeine.330... 

Caffeine, also known as theine, or methyltheobromine, 1,2,7-trimethyl xanthine (see structural formula in accompanying diagram), white, fleecy or long, flexible crystals. Caffeine effloresces in air and commences losing water at 80 C. Soluble in chloroform, slightly soluble in water and alcohol, very slightly soluble in ether, mp 236.8°C, odorless, bitter taste. Solutions are neutral to litmus paper. 

Methyl derivatives of xanthine (2,3-dioxypurine) namely caffeine (1,3,7-trimethyl-xanthine), theobromine (3,7-dimethylxanthine) and theophylline (1,3-dimethylxanthine) (Section 1, Appendix) are variously found in plants used for stimulatory drinks such as Ilex paraguayensis (mate) (Aquifoliaceae), Coffea species (coffee) (Rubiaceae), Paullinia cupana (guarana) (Sapindaceae), Cola acuminata (cola) and Theabroma cacao (cocoa) (Sterculiaceae) and Camellia sinensis (tea) (Theaceae). These methylxanthines are variously active as inhibitors of... 

Figure 6.37 Synthesis of an osmium carbene complex using 1,3,7-trimethyl xanthine as the...

In contrast to xanthine the isomeric 2,8- and 6,8-dioxo compounds have been little studied. However the presence of an oxo function in the imidazole ring ensures that alkylation will very readily and rapidly occur in that ring, followed generally by alkylation elsewhere. Thus in alkaline solution dimethyl sulfate converts 2,8-dioxo-l,2,7,8-tetra-hydropurine into a mixture of the 1,7- and the 1,9-dimethyl derivatives (111) and (112), respectively, in 10 minutes at room temperature, the former compound predominating (i4JBC07)i). Further alkylation then affords the 1,7,9-trimethylpurine (113). Similar products are formed with methyl iodide under more forcing conditions (100 °C, 1 h) and the latter also produces the 3,7,9-trimethyl derivative (114) from the 3-methyl-2,8-dioxo derivatives (i899CB272i). 

Caffeine and theine were shown to be tri-methyl xanthine or trimethyl di-hydroxy purine. 

Purine-2,6-diol 9H-Purine-2,6-diol Purine-2,6-(1 H,3H)-dione. See Xanthine 1H-Purine-2,6-dione, 3.7-dihydro-1,3,7-trimethyl-. See Caffeine... 

Purine alkaloids are methyl derivatives of xanthine. The most common purine alkaloid is 1,3,5-trimethykanthine, 1,3,7-trimethyl-lH-purine-2,6(3H,7H)-dione, known trivially as caffeine (10-38). It is accompanied by dimethykanthines theobromine, theophylline and paraxanthine and also by methykanthine heteroxanthine and methyluric acids, which are minority alkaloids, with the exception of cocoa and chocolate. Caffeine is found in the seeds, leaves and fruits of more than 60 species of plants. It is assumed that the purpose of accumulation of purine alkaloids by plants is the protection... 

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