title: N6,5'-Disubstituted adenosine derivatives as partial agonists for the human adenosine A3 receptor.
abstract: 5'-(Alkylthio)-substituted analogues of N6-benzyl- and N6-(3-iodobenzyl)adenosine were synthesized in 37-61% overall yields. The affinities of these compounds for the adenosine A1, A2A, and A3 receptors were determined using rat brain cortex, rat brain striata, and stably transfected human A3 receptors in HEK 293 cells, respectively. The compounds proved to be selective for the adenosine A3 receptor and displayed affinities in the nanomolar range. Compounds 8, 10, and 11 had the highest affinities for the A3 receptor with Ki values ranging from 8.8 to 27.7 nM. In the N6-benzyl series, compound 4 (LUF 5403), with a 5'-methylthio group, maintained a reasonable affinity and had the highest selectivity for the A3 receptor. Compound 12 (LUF 5411), with an N6-(3-iodobenzyl) group and a 5'-(n-propylthio) substituent, had the highest A3 selectivity of all of the compounds and also displayed high affinity for this receptor (Ki = 44.3 nM). The compounds were also evaluated for their ability to stimulate [35S]GTPgamma[S] binding in cell membranes expressing the human adenosine A3 receptor. It appeared that the N6,5'-disubstituted adenosine derivatives behaved as partial agonists. Compounds 2, 4, 8, and 10 had the highest intrinsic activities. Additionally, when tested in a cAMP assay, these compounds also behaved as partial agonists.
authors.affiliation: Division of Medicinal Chemistry, Leiden/Amsterdam Center for Drug Research, P.O. Box 9502, 2300 RA Leiden, The Netherlands. vtilburg@chem.leidenuniv.nl
authors.forename: E W
authors.initials: EW
authors.lastname: van Tilburg
authors.forename: J
authors.initials: J
authors.lastname: von Frijtag Drabbe Künzel
authors.forename: M
authors.initials: M
authors.lastname: de Groote
authors.forename: R C
authors.initials: RC
authors.lastname: Vollinga
authors.forename: A
authors.initials: A
authors.lastname: Lorenzen
authors.forename: A P
authors.initials: AP
authors.lastname: IJzerman
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D002540:Cerebral Cortex / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D006224:Cricetinae; D000242:Cyclic AMP / Q000096:biosynthesis; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D058906:Purinergic P1 Receptor Agonists; D011869:Radioligand Assay; D051381:Rats; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1 / Q000378:metabolism
chemical_list: D058906:Purinergic P1 Receptor Agonists; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000242:Cyclic AMP; D000241:Adenosine