Synthesis of novel (benzimidazolyl)isoquinolinols and evaluation as adenosine A1 receptor tools

Development and Application of Subtype-Selective Fluorescent Antagonists for the Study of the Human Adenosine A1 Receptor in Living Cells

The adenosine A₁ receptor (A₁AR) is a G-protein-coupled receptor (GPCR) that provides important therapeutic opportunities for a number of conditions including congestive heart failure, tachycardia, and neuropathic pain. The development of A₁AR-selective fluorescent ligands will enhance our understanding of the subcellular mechanisms underlying A₁AR pharmacology facilitating the development of more efficacious and selective therapies. Herein, we report the design, synthesis, and application of a novel series of A₁AR-selective fluorescent probes based on 8-functionalized bicyclo[2.2.2]octylxanthine and 3-functionalized 8-(adamant-1-yl) xanthine scaffolds. These fluorescent conjugates allowed quantification of kinetic and equilibrium ligand binding parameters using NanoBRET and visualization of specific receptor distribution patterns in living cells by confocal imaging and total internal reflection fluorescence (TIRF) microscopy. As such, the novel A₁AR-selective fluorescent antagonists described herein can be applied in conjunction with a series of fluorescence-based techniques to foster understanding of A₁AR molecular pharmacology and signaling in living cells.

Mild Synthesis of Fluorosolvatochromic and Acidochromic 3-Hydroxy-4-pyridylisoquinoline Derivatives from Easily Available Substrates

The reaction of sodium cyanate with benzo[ b]quinolizinium substrates at room temperature gave 3-hydroxy-4-pyridyl-isoquinoline derivatives in good yields. Presumably, the overall reaction proceeds through an ANRORC-type sequence, that is, addition of the nucleophile, ring opening, and ring closure. Preliminary photophysical investigation of the parent compound revealed a pronounced sensitivity of its emission properties toward solvent effects and the pH of the medium.