2-Phenylpyrazolo[4,3-d]pyrimidin-7-one as a New Scaffold To Obtain Potent and Selective Human A3 Adenosine Receptor Antagonists: New Insights into the Receptor−Antagonist Recognition
摘要:
A molecular simplification approach of previously reported 2-arylpyrazolo[3,4-c]quinolin-4-ones was applied to design 2-arylpyrazolo[4,3-d]pyrimidin-7-one derivatives as new human A(3) adenosine receptor antagonists. Substituents with different lipophilicity and steric hindrance were introduced at the 5-position of the bicyclic Scaffold (R-5 = H, Me, Et, Ph, CH2Ph) and on the 2-phenyl ring (OMe, Me). Most of the synthesized derivatives were highly potent hA(3) adenosine receptor antagonists, the best being the 2-(4-methoxyphenyl)pyrazolo[4,3-d]pyrimidin-7-one (K-i = 1.2 nM). The new compounds were also highly selective, being completely devoid of affinity toward hA(1), hA(2A), and hA(2B) adenosine receptors. On the basis of the recently published human A(2A) receptor crystallographic information, we propose it novel receptor-driven hypothesis to explain both A(3) AR affinity and A(3) versus A(2A) Selectivity profiles of these new antagonists.
Improved Protocol for Thorpe Reaction: Synthesis of 4‐Amino‐1‐arylpyrazole using Solid–Liquid Phase‐Transfer Conditions
摘要:
Solid - liquid phase-transfer conditions were employed for the first time in the Thorpe reaction to synthesize 4-amino-1-aryl-3,5-substituted-1H-pyrazoles 3. Aryl amines were diazotized and coupled with various active methylene compounds such as cyano acetamide, cyanoacetophenone, malononitrile, and ethyl cyanoacetate, resulting into alpha-arylhydrazononitriles 1. Cyclization of 1 using alpha-bromo ketones or esters resulted in compounds 3.