Xanthine, 3,7-Dimethyl

Paraxanthine—see Xanthine, 1,7-dimethyl-Parent name nomenclature, 1, 35 Parham cycloalkylation in chroman synthesis, 3, 783 Paromomycins as pharmaceuticals, 1, 154 Partial charge transfer from donor to acceptor stacks, 1, 350 Pasteurellosis... 

A solution of 35.4 g of 1 -bromohexanone-5 in 200 ml of ethanol was gradually mixed at the reflux temperature with vigorous stirring with 39.7 g of theobromine-sodium in 100 ml of water. After 3 hours reflux the unreacted theobromine was filtered off with suction, the fil-trete was evaporated to dryness, the residue was dissolved in water and the solution was extracted with chloroform. The chloroform was distilled off and 1-(5 -oxohexyl)-3,7-dimethyl-xanthine was obtained as residue after recrystellization from isopropanol, it melted at 102°C to 103°C (about 25% yield, calculated on the reacted theobromine). 

The enzymes that utilize molybdenum can be grouped into two broad categories (1) the nitrogenases, where Mo is part of a multinu-clear metal center, or (2) the mononuclear molybdenum enzymes, such as xanthine oxidase (XO), dimethyl sulfoxide (DMSO) reductase, formate dehydrogenase (FDH), and sulfite oxidase (SO). The last... 

HPLC coupled to MS was used for the determination of dimethyl xanthine metabolites in plasma.82 There have also been a number of methods published on the use of HPLC with a PDA detector. In 1996, Mei published a method for the determination of adenosine, inosine, hypoxanthine, xanthine, and uric acid in microdialysis samples using microbore column HPLC with a PDA detector.63 In this method, samples were directly injected onto the HPLC without the need for any additional sample treatment. 

Sulfur atom as internal nucleophile. In this area, it has been shown that the reaction of 8-bromo-l,3-dimethyl-7-(2,3-epithiopropyl)xanthine 147 with a range of aliphatic and aromatic amines generates efficiently 2-amino-substituted 2,3-dihydro-thiazolo[2,3-/]xanthine derivatives 148. The process involves a sequential amine-induced thiirane ring opening followed by thiolate z/MYi-substitution of chlorine atom (Equation 66) <1994PCJ647>. 

Theophylline (Fig. 20) is structurally very similar to caffeine and present at a low concentration in tea. It is also known as dimethyl xanthine. It is used for the treatments of asthma and COPD, for more than 50 years despite its many side effects. The mechanism of beneficial effect of theophylline is through HD AC activation. 

Synthesis of l,8-dimethyl-3-(2-methyl-l-butyl)xanthine included 7 steps ... 

Theobromine was isolated from the seeds of the cacao tree and then shortly afterward was synthesized from xanthine by Fischer.132 Theobromine is the primary bitter-tasting alkaloid found in cocoa and chocolate chocolate contains 0.5—2.7% theobromine. Theobromine is water insoluble and is an isomer of theophylline as well as paraxanthine. Theobromine is categorized as 3,7-dimethylxanthine while theophylline is 1,3-dimethyl-7f/-purine-2,6-dione and paraxanthine is 1,7-dimethylxanthine. Theophylline is known to be a bitter-tasting principle of green tea. Theobromine is used as a vasodilator (a blood vessel widener), as an aid in urination, and... 

Instead of xanthine, 7,9-dimethyl-8-thioureic acid [76,78] can be used as the starting material. In the early days, metallation to a transition metal NHC complex was not attempted. This started in the mid 1970s when Taube and coworkers synthesised a ruthenium carbene complex [79] (see Figure 6.33) and realised that the imidazole can be replaced by a purine [80,81],... 

SYNS 3,7-DIHYDRO-3,7-DIMETHYL-lH-PURINE-2,6-DIONE 3,7-DLMETHYI.XANTHINE DIUROBROM-INE SANTHEOSE O SC 15090 O TEOBROMIN D THEOSALVOSE THEOSTENE THESAL THESODATE... 

The naturally occurring purines fall into 4 main groups. (1) Simple substituted derivatives of purine (1) such as adenine (2) and various 6-AT-substituted derivatives. (2) Monoxo-dihydropurines such as hypoxanthine (3), guanine (4), and isoguanine (5). f3) Dioxotetra-hydropurines such as xanthine (6) and methylated derivatives including the 3,7-dimethyl derivative theobromine (7), 1,3-dimethylxanthine or theophylline f8), and 1,3,7-trimethylxanthine or caffeine (9). (4) Trioxohexahydropurines such as uric acid (10). 

In alkaline solutions, xanthine alkylates on nitrogen in the order N-3, N-7, N-1, i.e. in decreasing order of acidity, and substitution is easier when the first position has been alkylated so to this extent dialkyl derivatives tend to be most easily produced. Thus 3,7-dimethylxanthine (theobromine) is produced by methylation of xanthine or 3-methylxanthine with methyl iodide and barium carbonate (33JCS662) or dimethyl sulfate in potassium hydroxide at 60 °C (50CB201). However when the oxygen functions are blocked by trimethylsilylation, alkylation occurs at N-7 (64CB934). 

Further methylation of theobromine readily produces caffeine (31MI40900). Similarly, 1-methylxanthine is methylated by dimethyl sulfate in alkaline solution to furnish 1,3-dimethylxanthine (theophylline) which is further converted into caffeine (31MI40900). Scheme 18 outlines the major stages of xanthine alkylation. 

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