Search for New Purine- and Ribose-Modified Adenosine Analogs as Selective Agonists and Antagonists at Adenosine Receptors
作者:Suhaib M. Siddiqi、Kenneth A. Jacobson、John L. Esker、Mark E. Olah、Xiao-duo Ji、Neli Melman、Kamal N. Tiwari、John A. Secrist、Stewart W. Schneller
DOI:10.1021/jm00007a014
日期:1995.3
The binding affinities at rat A(1), A(2a), and A(3) adenosine receptors of a wide range of derivatives of adenosine have been determined. Sites of modification include the purine moiety (1-, 3-, and 7-deaza; halo, alkyne, and amino substitutions at the 2- and 8-positions; and N6(-)CH(2)-ring, -hydrazino, and -hydroxylamino) and the ribose moiety (2'-, 3'-, and 5'-deoxy; 2'- and 3'-O-methyl;2'-deoxy 2'-fluoro;6'-thio;5'-uronamide;carbocyclic;4'- or 3'-methyl; and inversion of configuration. (-)- and (+)-5'-Noraristeromycin were 48- and 21-fold selective, respectively, for A(2a), vs A(1) receptors. 2-Chloro-6'-thioadenosine displayed a K-i value of 20 nM at A(2a) receptors (15-fold selective vs A(1)). 2-Chloroadenin-9-yl(beta-L-2'-deoxy-6'-thiolyxofuranoside) displayed a K-i value of 8 mu M at A(1) receptors and appeared to be an antagonist, on the basis of the absence of a GTP-induced shift in binding vs a radiolabeled antagonist (8-cyclopentyl-1,3-dipropylxanthine). 2-Chloro-2'-deoxyadenosine and 2-chloroadenin-9-yl(beta-D-6'-thioarabinoside) were putative partial agonists at A(1) receptors, with K-i values of 7.4 and 5.4 mu M, respectively. The A(2a) selective agonist 2-(1-hexynyl)-5'-(N-ethylcarbamoyl)adenosine displayed a K-i value of 26 nM at A(3) receptors. The 4'-methyl substitution of adenosine was poorly tolerated, yet when combined with other favorable modifications, potency was restored. Thus, N-6-benzyl-4'methyladenosine-5'-(N-methyluronamide) displayed a K-i value of 604 nM at A(3) receptors and was 103- and 88-fold selective vs A(1) and A(2a) receptors, respectively. This compound was a full agonist in the A(3)-mediated inhibition of adenylate cyclase in transfected CHO cells. The carbocyclic analogue of N-6-(3-iodobenzyl)adenosine-5'-(N-methyluronamide) was 2-fold selective for A(3) VS A(1) receptors and was nearly inactive at A(2a) receptors.