Solid phase synthesis of 1,5-diarylpyrazole-4-carboxamides: discovery of antagonists of the CB-1 receptor

We have developed a solid phase synthesis route to 1,5-substituted pyrazole-4-carboxamides with three diversity points aimed at the discovery of new compounds as potential G-Protein coupled receptor (GPCR) ligands. The new chemistry involves acylation of a resin bound secondary amine with a β-ketoester via transamidation, conversion of the resulting β-ketoamide to the corresponding vinylogous amide, pyrazole formation upon reaction with a aryl hydrzine, and cleavage of the product from the resin. Using the reported methodology, we describe the syntheses of multiple arrays of pyrazoles that were used collectively to construct a library of more than 1000 analogues. Several members of this library displayed submicromolar antagonist activities at the cannabinoid subtype 1 (CB-1) receptor.