Xanthines, 8-phenyl

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... 

Xanthine, 9-methyl-8-methylthio-2-thio-synthesis, S, 590 Xanthine, 7-methyl-8-phenyl-synthesis, S, 588 Xanthine, 7-methyl-2-thio-synthesis, S, 590 Xanthine, 9-methyl-2-thio-synthesis, 5, 590 Xanthine, 8-methylthio-2-thio-synthesis, S, 590... 

Complexation with caffeine and theophylline-7-acetate depresses the rate of alkaline hydrolysis of substituted phenyl benzoates and is consistent with the formation of molecular complexes with 1 1 stoichiometry between the hosts and esters stacking of the xanthines is excluded as an explanation in the range of concentrations studied. Inhibition of hydrolysis is attributed to repulsion of the hydroxide ion from the host-ester complex by the extra hydrophobicity engendered by the xanthine host, as well as by the weaker binding of the transition state to the host compared with that in the host-ester complex. ... 

The interrelationship between the 2- and 8-positions is exemplified by 2-oxo-103 and 8-oxopurine, which are both converted by xanthine oxidase to 2,8-dioxopurine. Some unexpected results of oxidation can best be explained by assuming stereospecific factors. Thus, whereas purine, its 2-methyl, and its 2-amino derivatives give the 6-oxo derivatives, the 2-phenyl- and 2-oxopurines mentioned above oxidize at the 8-position.112... 

Phenyl-l,2,3-triazolo[4,5-d]pyrimidin-7(6//)-one has bactericidal activity against Bacillus subtilis and Staphylococcus aureus (94MI2). 1-Benzyl-4-ethoxycarbonylpiperazinyl-l//-l,2,3-triazolo[4,5-d]pyrimidine almost completely removed cytokinin-stimulated effects in betacyanin synthesis in Amaranthus caudatus cotyledons, growth of radish cotyledons, and retention of chlorophyll in leaf explants (94MI4). Analogs of 117 were used as effective inhibitors of xanthine oxidase (95FA257). 

Reaction of benzylaminouracil with DAD affords xanthines via a Michael addition and internal disproportionation reaction [75CC146 77JCS(P1 )1754]. The Michael adduct of 4-phenyl-l,2,4-triazoline-3,5-dione (PTAD) is easily converted into xanthines on heating with aromatic aldehydes [74CC551 77JCS(P1)2285]. Insoferevenulin can be pre-... 

Condensation of 6-amino-5-nitrosouracils with ethanethiol and phenyl-methanethiol leads to formation of 8-substituted xanthines and 1,2,5-thiadiazolo[3,4-t/]pyrimidines [75JCS(P1) 1857]. Oxidation with lead tetraacetate forms furazano[3,4-with sodium nitrite or potassium nitrate and subsequent heating in DMF [73JHC415, 73JHC993 76JCS(P 1) 1327] (Scheme 65). 

Reactions of 5-nitrosobarbituric acids with aminoguanidine, of 5-phen-ylazobarbituric acids with phenethylamine, and of 5-arylmethylene-aminobarbituric acid with NBS or thionyl chloride afford isofervenu-lins, 8-phenyl-xanthines, and oxazolo[5,4-t/]pyrimidines, respectively [75BCJ725, 75BCJ1679 77H(6)689, 77H(6)1901, 77H(6)1919 78CPB765] (Scheme 75). 

Methoxy-, 6-ethoxy-, and 6-methylthio-9-ribofuranosyl-8-azapurines turned out to be substrates for adenosine kinase, and the first two examples were bound by adenosine deaminase. Their cytotoxic action was attributed to affinity for the kinase. 6-Imino-9-phenyl-l,6-dihydro-8-azapurine was found to be an efficient inhibitor of adenosine deaminase and guanine deaminase. Xanthine oxidase was inhibited by both this compound and 9-aryl-8-azapurin-6-ones. ° ... 

Goto T, Takagi T. Chemilluminescence of a Cypridina luciferin analogue, 2-methyl-6-phenyl-3,7-dihydroimidazo[l,2-a]pyrazin-3-one, in the presence of the xanthine-xanthine oxidase system. Bull Chem Soc Jpn 1980 53 833-4. 

Simple unsubstituted monocycles such as pyridine, pyrazine, pyrimidine, pyridazine and pyrrole show little or negligible binding to either enzyme [3, 10, 173], However, we have shown that fusion or substitution of a phenyl group significantly increases the affinity of the compounds towards aldehyde oxidase, and in some cases the heterocycles are substrates for xanthine oxidase (Table 3.6) [50, 173]. Furthermore, studies with compounds containing a... 

Xanthates. See Carbonodithioates 9/f-Xanthene, 9-chloro-9-phenyl- pixyl O-protection with, 341-324 Xanthine = 3,7-dihydro-ltf-purine-2,6-dione synthesis and methylation, 306 Xanthine alkaloids pr., 290 caffeine, 306... 

As part of programmes directed towards the synthesis of new potential biologically active compounds, a variety of cyclic xanthine derivatives, e.g., (37) and (38), have been prepared by Russian workers." During a detailed study aimed at elucidating modes of alkylation of purines, treatment of 6-methylthio-8-phenyl-purine (39 R = H) with methyl iodide in DMF was shown to yield a single methiodide, which upon hydrolysis gave exclusively the 3-methyl derivative (40). Similarly, the 7-methyl and 7-methyl analogues, (41) and (42), yielded 3-methyl... 

Glc] with phenyl isocyanlde dlchloride (PhN=CCl2)and an N-glucosylated xanthine derivative has been obtained by cyclization... 

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