Derivatives of the triazoloquinazoline adenosine antagonist (CGS15943) are selective for the human A3 receptor subtype

J Med Chem. 1996 Oct 11;39(21):4142-8. doi: 10.1021/jm960482i.


The adenosine antagonist 9-chloro-2-(2-furanyl)[1,2,4]triazolo[1,5-c]quinazolin-5-amine (CGS15943) binds to human A3 receptors with high affinity (Ki = 14 nM), while it lacks affinity at rat A3 receptors. Acylated derivatives of the 5-amino group and other modifications were prepared in an effort to provide A3 subtype selectivity. Affinity was determined in radioligand binding assays at rat brain A1 and A2A receptors using [3H]-(R)-PIA ([3H]-(R)-N6-(phenylisopropyl)-adenosine) and [3H]CGS 21680 ([3H]-2-[[4-(2-carboxy ethyl)phenyl]ethylaminol]-5'-(N- ethyl- carbamoyl)adenosine), respectively. Affinity was determined at cloned human A3 receptors using [125I]AB-MECA (N6-(4-amino-3-iodobenzyl)-5'-(N-methylcarbamoyl)adenosine). A series of straight chain alkyl amides demonstrated that the optimal chain length occurs with the 5-N-propionyl derivative, 3, which had a Ki value of 7.7 nM at human A3 receptors, and was 40- and 14-fold selective vs rat A1 and A2A receptors, respectively. The 5-N-benzoyl derivative, 10, displayed Ki values of 680 and 273 nM at rat A1 and A2A receptors, respectively, and 3.0 nM at human A3 receptors. A 5-N-phenylacetyl derivative, 12, was 470-fold selective for human A3 vs rat A1 receptors with a Ki value of 0.65 nM. A conjugate of Boc-gamma-aminobutyric acid was also prepared but was nonselective. Conversion of the 5-amino group of CGS15943 to an oxo function resulted in lower affinity but 15-fold selectivity for human A3 receptors.

MeSH terms

  • Adenosine / analogs & derivatives
  • Adenosine / chemistry
  • Adenosine / metabolism
  • Affinity Labels / metabolism
  • Animals
  • Binding Sites
  • Binding, Competitive
  • Cell Line
  • Cerebral Cortex / metabolism
  • Corpus Striatum / metabolism
  • Humans
  • Magnetic Resonance Spectroscopy
  • Quinazolines / chemistry
  • Quinazolines / metabolism*
  • Rats
  • Receptors, Purinergic P1 / metabolism*
  • Structure-Activity Relationship
  • Substrate Specificity
  • Triazoles / chemistry
  • Triazoles / metabolism*


  • Affinity Labels
  • Quinazolines
  • Receptors, Purinergic P1
  • Triazoles
  • N(6)-(4-amino-3-iodobenzyl)adenosine-5'-N-methyluronamide
  • Adenosine
  • 9-chloro-2-(2-furyl)-(1,2,4)triazolo(1,5-c)quinazolin-5-imine