Quinazolines as adenosine receptor antagonists: SAR and selectivity for A2B receptors Original Research Article

We have recently reported the discovery of numerous new compounds that are selective inhibitors of all of the subtypes of the adenosine receptor family via a pharmacophore database searching and screening strategy. During the course of this work we made the unexpected discovery of a potent A2B receptor antagonist, 4-methyl-7-methoxyquinazolyl-2-(2′-amino-4′-imidazolinone) (38, CMB 6446), which showed selectivity for this receptor and functioned as an antagonist, with a binding Ki value of 112 nM. We explored the effects of both substituent- and ring-structural variations on the receptor affinity in this series of derivatives, which were found to be mostly non-selective adenosine receptor ligands with Ki values in the micromolar range. Since no enhancement of A2B receptor affinity of 38 was achieved, the previously reported pharmacophore-based searching strategy yielded the most potent and selective structurally-related hit in the database originally searched.