title: 2-triazole-substituted adenosines: a new class of selective A3 adenosine receptor agonists, partial agonists, and antagonists.
abstract: "Click chemistry" was explored to synthesize two series of 2-(1,2,3-triazolyl)adenosine derivatives (1-14). Binding affinity at the human A(1), A(2A), and A(3)ARs (adenosine receptors) and relative efficacy at the A(3)AR were determined. Some triazol-1-yl analogues showed A(3)AR affinity in the low nanomolar range, a high ratio of A(3)/A(2A) selectivity, and a moderate-to-high A(3)/A(1) ratio. The 1,2,3-triazol-4-yl regiomers typically showed decreased A(3)AR affinity. Sterically demanding groups at the adenine C2 position tended to reduce relative A(3)AR efficacy. Thus, several 5'-OH derivatives appeared to be selective A(3)AR antagonists, i.e., 10, with 260-fold binding selectivity in comparison to the A(1)AR and displaying a characteristic docking mode in an A(3)AR model. The corresponding 5'-ethyluronamide analogues generally showed increased A(3)AR affinity and behaved as full agonists, i.e., 17, with 910-fold A(3)/A(1) selectivity. Thus, N(6)-substituted 2-(1,2,3-triazolyl)adenosine analogues constitute a novel class of highly potent and selective nucleoside-based A(3)AR antagonists, partial agonists, and agonists.
authors.affiliation: Laboratory for Medicinal Chemistry, Faculty of Pharmaceutical Sciences (FFW), Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium.
authors.forename: Liesbet
authors.initials: L
authors.lastname: Cosyn
authors.forename: Krishnan K
authors.initials: KK
authors.lastname: Palaniappan
authors.forename: Soo-Kyung
authors.initials: SK
authors.lastname: Kim
authors.forename: Heng T
authors.initials: HT
authors.lastname: Duong
authors.forename: Zhan-Guo
authors.initials: ZG
authors.lastname: Gao
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Jacobson
authors.forename: Serge
authors.initials: S
authors.lastname: Van Calenbergh
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000494:pharmacology; D058909:Adenosine A3 Receptor Agonists; D058918:Adenosine A3 Receptor Antagonists; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D000242:Cyclic AMP / Q000096:biosynthesis; D006801:Humans; D008958:Models, Molecular; D011869:Radioligand Assay; D013329:Structure-Activity Relationship; D014230:Triazoles / Q000138:chemical synthesis* / Q000494:pharmacology
chemical_list: D058909:Adenosine A3 Receptor Agonists; D058918:Adenosine A3 Receptor Antagonists; D014230:Triazoles; D000242:Cyclic AMP; D000241:Adenosine