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Publication . Article . 1994

Selective Ligands for Rat A3 Adenosine Receptors: Structure-Activity Relationships of 1,3-Dialkylxanthine 7-Riboside Derivatives

Hea Ok Kim; Xiao-duo Ji; Neli Melman; Márk Oláh; Gary L. Stiles; Kenneth A. Jacobson;
Open Access
Published: 01 Nov 1994 Journal: Journal of Medicinal Chemistry, volume 37, pages 4,020-4,030 (issn: 0022-2623, eissn: 1520-4804, Copyright policy )
Publisher: American Chemical Society (ACS)
Abstract
1,3-Dibutylxanthine 7-riboside has been found to be a partial agonist at A3 adenosine receptors (van Galen et al. Mol. Pharmacol. 1994, 45, 1101-1111). 1,3-Dialkylxanthine 7-riboside analogues modified at the 1-, 3-, and 8-purine positions and at the ribose 5'-position were synthesized. The nucleoside analogues were examined for affinity in radioligand binding assays at rat brain A3 adenosine receptors stably expressed in CHO cells, using the radioligand [[125I]-4-amino-3-iodobenzyl]adenosine-5'-N-methyluronamide (AB-MECA). Affinity was assayed at rat brain A1 and A2a receptors using [3H]PIA and [3H]CGS 21680, respectively. The affinity of xanthine 7-ribosides at A3 receptors depended on the 1,3-dialkyl substituents in the order: Pent > or = Bu >> Hx > Pr approximately Me. 1,3-Dipentylxanthine 7-riboside was slightly selective for A3 receptors (2-fold vs A1 and 10-fold vs A2a). 8-Methoxy substitution was tolerated at A3 receptors. 2-Thio vs 2-oxo substitution increased potency at all three subtypes and slightly increased A3 vs A1 selectivity. The 5'-uronamide modification, which was previously found to enhance A3 selectivity in N6-benzyladenosine derivatives, was also incorporated into the xanthine 7-ribosides, with similar results. The affinity of 1,3-dialkylxanthine 7-riboside 5'-uronamides at A3 receptors depended on the N-alkyluronamide substituent in the order: MeNH > EtNH >> NH2 >> Me2N. Affinity of the 5'-uronamides at A3 receptors was dependent on the 1,3-dialkyl substitution in the order: Bu > Pent > Hex. 1,3-Dibutylxanthine 7-riboside 5'-N-methylcarboxamide, with a Ki value of 229 nM at A3 receptors, was 160-fold selective for rat A3 vs A1 receptors and > 400-fold selective vs A2a receptors. This derivative acted as a full agonist in the A3 receptor-mediated inhibition of adenylate cyclase.
Subjects by Vocabulary

Microsoft Academic Graph classification: Agonist medicine.drug_class medicine Receptor Radioligand Adenosine receptor CGS-21680 chemistry.chemical_compound chemistry Riboside Adenosine A1 receptor Stereochemistry Nucleoside

Subjects

Drug Discovery, Molecular Medicine

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