- Synthesis and biological evaluation of disubstituted N6- cyclopentyladenine analogues: The search for a neutral antagonist with high affinity for the adenosine A1 receptor
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Novel 3,8- and 8,9-disubstituted N6-cyclopentyladenine derivatives were synthesised in moderate overall yield from 6-chloropurine. The derivatives were made in an attempt to find a new neutral antagonist with high affinity for adenosine A1 receptors. N6-Cyclopentyl-9- methyladenine (N-0840) was used as a lead compound. Binding affinities of the new analogues were determined for human adenosine A1 and A 3 receptors. Their intrinsic activity was assessed in [ 35S]GTPγS binding experiments. Elongation of the 9-methyl of N-0840 to a 9-propyl substituent was very well tolerated. A 9-benzyl group, on the other hand, caused a decrease in adenosine A1 receptor affinity. Next, the 8-position was examined in detail, and affinity was increased with appropriate substitution. Most derivatives were A1-selective and 20 of the new compounds (6-9, 15-21, 23-26, 28, 31, 33, 35, and 36) had higher adenosine A1 receptor affinity than the reference substance, N-0840. Compound 31 (N6-cyclopentyl-8-(N-methylisopropylamino)-9- methyladenine, LUF 5608) had the highest adenosine A1 receptor affinity, 7.7 nM. In the [35S]GTPγS binding experiments, derivatives 5, 14, 22, 23, 25, 26, 33 and 34 did not significantly change basal [35S]GTPγS binding, thus behaving as neutral antagonists. Moreover, four of these compounds (23, 25, 26, and 33) displayed a 4- to 10-fold increased adenosine A1 receptor affinity (75-206 nM) compared to N-0840 (852 nM). In summary, we synthesised a range of N-0840 analogues with higher affinity for adenosine A1 receptors. In addition, four new derivatives, LUF 5666 (23), LUF 5668 (25), LUF 5669 (26) and LUF 5674 (33), behaved as neutral antagonists when tested in [ 35S]GTPγS binding studies. Thus, these compounds have improved characteristics as neutral adenosine A1 receptor antagonists.
- De Ligt, Rianne A. F.,Van Der Klein, Pieter A. M.,Von Frijtag Drabbe Kuenzel, Jacobien K.,Lorenzen, Anna,El Maate, Fatna Ait,Fujikawa, Shelly,Van Westhoven, Rosemarijn,Van Den Hoven, Thijs,Brussee, Johannes,Ijzerman, Ad P.
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p. 139 - 149
(2007/10/03)
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- COMPOSITION FOR DETERMINING VIABILITY OF TISSUE
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A method and composition of determining the viability of tissue in a region of an organism having a vascular circulatory system that supplies blood to said region is disclosed. The composition includes the combination of adenosine or an adenosine antagonist in combination with an A 1 adenosine receptor which may be: STR1 wherein R 1 is hydrogen or R 2 ; R 2 is selected from the group consisting of endo-2-norbornyl or cyclopentyl; R 3 is selected from the group consisting of hydrogen, halogen, amine, carboxy, alkyl radicals having 1 to 10 carbon atoms, cycloalkyl radicals having from 3 to 8 ring carbon atoms, thio sulfonate, sulfonamide, sulfone, sulfoxamide, phenyl, alkyl-substituted amine, and cycloalkyl substituted amine; R 4 is selected from the group consisting of benzyl, phenyl, alkyl groups comprising from 1 to 4 carbon atoms, wherein said alkyl group can be substituted with oxygen, for instance ethers and alcohols; and R 5 is selected from the group consisting of hydrogen, hydroxy, sulfonate, halogen, alkoxy and cycloalkoxy groups comprising 1 to 6 carbon atoms.
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- N6,9-Disubstituted Adenines: Potent, Selective Antagonists at the A1 Adenosine Receptor
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N6-Substituted 9-methyladenines are potent antagonists of the activation of A1 adenosine receptors.The present study assessed the effect of N6 and N-9-substituents on the binding of adenines to the A1 and A2 receptors, respectively, of rat brain cortex and striatum and also on the antagonism of the A2 receptor mediated stimulation of the adenylate cyclase of PC12 cells by N-ethyladenosine-5'-uronamide.The potency ranking of 9-substituted adenines varied directly with the hydrophobicity of the substituent: cyclopentyl > phenyl > tetrahydrofuryl > ethyl > methyl > 2-hydroxyethyl.The 9-substituted adenines showed little selectivity for either receptor and the R enantiomer of N6-(1-phenyl-2-propyl)-9-methyladenine was only 4-fold more potent than the S enantiomer at the A1 receptor.An N6-cyclopentyl substituent increased potency at the A1 receptor and decreased potency at the A2 receptor, resulting in selectivity for the A1 receptor of up to 39-fold.The N6-cyclopentyl group completely overshadowed the effect of the hydrophobicity of the 9-substituent.A 2-chloro substituent did not alter the potency of an N6-substituted 9-methyladenine.
- Thompson, Robert D.,Secunda, Sherrie,Daly, John W.,Olsson, Ray A.
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p. 2877 - 2882
(2007/10/02)
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