| Abstract
| - The P2Y1 receptor is present in the heart, in skeletal and various smooth muscles, and inplatelets, where its activation is linked to aggregation. Adenosine 3‘,5‘- and 2‘,5‘-bisphosphateshave been identified as selective antagonists at the P2Y1 receptor (Boyer et al. Mol. Pharmacol.1996, 50, 1323−1329) and have been modified structurally to increase receptor affinity(Camaioni et al. J. Med. Chem.1998, 41, 183−190). We have extended the structure−activityrelationships to a new series of deoxyadenosine bisphosphates with substitutions in the adeninebase, ribose moiety, and phosphate groups. The activity of each analogue at P2Y1 receptorswas determined by measuring its capacity to stimulate phospholipase C in turkey erythrocytemembranes (agonist effect) and to inhibit phospholipase C stimulation elicited by 10 nM2-(methylthio)adenosine 5‘-diphosphate (antagonist effect). 2‘-Deoxyadenosine bisphosphateanalogues containing halo, amino, and thioether groups at the 2-position of the adenine ringwere more potent P2Y1 receptor antagonists than analogues containing various heteroatomsubstitutions at the 8-position. An N6-methyl-2-chloro analogue, 6, was a full antagonist anddisplayed an IC50 of 206 nM. Similarly, N6-methyl-2-alkylthio derivatives 10, 14, and 15 werenearly full antagonists of IC50< 0.5 μM. On the ribose moiety, 2‘-hydroxy, 4‘-thio, carbocyclic,and six-membered anhydrohexitol ring modifications have been prepared and resulted inenhanced agonist properties. The 1,5-anhydrohexitol analogue 36 was a pure agonist with anEC50 of 3 μM, i.e., similar in potency to ATP. 5‘-Phosphate groups have been modified in theform of triphosphate, methyl phosphate, and cyclic 3‘,5‘-diphosphate derivatives. The carbocyclicanalogue had enhanced agonist efficacy, and the 5‘-O-phosphonylmethyl modification wastolerated, suggesting that deviations from the nucleotide structure may result in improvedutility as pharmacological probes. The N6-methoxy modification eliminated receptor affinity.Pyrimidine nucleoside 3‘,5‘-bisphosphate derivatives were inactive as agonists or antagonistsat P2Y receptor subtypes.
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