title: Trifunctional agents as a design strategy for tailoring ligand properties: irreversible inhibitors of A1 adenosine receptors.
abstract: The 1,3-phenylene diisothiocyanate conjugate of XAC (8-[4-[[[[(2-aminoethyl)amino]carbonyl]methyl]- oxy]phenyl]-1,3-dipropylxanthine, a potent A1 selective adenosine antagonist) has been characterized as an irreversible inhibitor of A1 adenosine receptors. To further extend this work, a series of analogues were prepared containing a third substituent in the phenyl isothiocyanate ring, incorporated to modify the physiochemical or spectroscopic properties of the conjugate. Symmetrical trifunctional cross-linking reagents bearing two isothiocyanate groups were prepared as general intermediates for cross-linking functionalized congeners and receptors. Xanthine isothiocyanate derivatives containing hydrophilic, fluorescent, or reactive substituents, linked via an amide, thiourea, or methylene group in the 5-position, were synthesized and found to be irreversible inhibitors of A1 adenosine receptors. The effects of the 5-substituent on water solubility and on the A1/A2 selectivity ratio derived from binding assays in rat brain membranes were examined. Inhibition of binding of [3H]-N6-(2-phenylisopropyl)-adenosine and [3H] CGS21680 (2-[2-[4-carboxyethyl)phenyl]ethyl]amino] adenosine-5'-N-ethylcarboxamide) at central A1 and A2 adenosine receptors, respectively, was measured. A conjugate of XAC and 1,3,5-triisothiocyanatobenzene was 894-fold selective for A1 receptors. Reporter groups, such as fluorescent dyes and a spin-label, were included as chain substituents in the irreversible binding analogues, which were designed for spectroscopic assays, histochemical characterization, and biochemical characterization of the receptor protein.
authors.affiliation: Laboratory of Bioorganic Chemistry, National Institute of Diabetes, and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: D L
authors.initials: DL
authors.lastname: Boring
authors.forename: X D
authors.initials: XD
authors.lastname: Ji
authors.forename: J
authors.initials: J
authors.lastname: Zimmet
authors.forename: K E
authors.initials: KE
authors.lastname: Taylor
authors.forename: G L
authors.initials: GL
authors.lastname: Stiles
authors.forename: K A
authors.initials: KA
authors.lastname: Jacobson
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D002417:Cattle; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000138:chemical synthesis / Q000378:metabolism; D015195:Drug Design; D066298:In Vitro Techniques; D017879:Isothiocyanates; D007700:Kinetics; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D010627:Phenethylamines / Q000378:metabolism; D010660:Phenylisopropyladenosine / Q000378:metabolism; D058914:Purinergic Antagonists; D051381:Rats; D011983:Receptors, Purinergic / Q000737:chemistry; D012995:Solubility; D013861:Thiocyanates / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology; D014970:Xanthines / Q000138:chemical synthesis* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D003432:Cross-Linking Reagents; D017879:Isothiocyanates; D008024:Ligands; D010627:Phenethylamines; D058914:Purinergic Antagonists; D011983:Receptors, Purinergic; D013861:Thiocyanates; D014970:Xanthines; C070252:8-(4-(((((2-((((3-isothiocyanatophenyl)amino)(thiocarbonyl))amino)ethyl)amino)carbonyl)methyl)oxy)phenyl)-1,3-dipropylxanthine; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D010660:Phenylisopropyladenosine; D000241:Adenosine