A convergent synthetic study of biologically active benzofuran derivatives.

In order to construct a benzofuran library, we developed a model study of benzbromarone. Synthesis has been achieved in 53% overall yield, starting from phenol via the key intermediate 2-ethylbenzofuran which was afforded by intramolecular Wittig reaction.

Quantitative binding models for CYP2C9 based on benzbromarone analogues.

The cytochrome P450 (CYP) isoforms involved in xenobiotic metabolism are enzymes whose substrate selectivity remains difficult to predict due to wide specificity and dynamic protein-substrate interactions. To uncover the determinants of specificity for cytochrome CYP2C9, a novel library of benzbromarone (bzbr) inhibitors was used to reevaluate its pharmacophore. CoMSIA was used with the bzbr ligands to generate both quantitative binding models and three-dimensional contour plots that pinpoint predicted interactions that are important for binding to 2C9. Since this class of compounds is more potent than any other toward 2C9, the small molecule properties deemed most ideal by the software were used to address protein-ligand interactions using new mutagenesis and structural data. Nine new bzbr analogues provide evidence that specific electrostatic and hydrophobic interactions contribute the most to 2C9's specificity. Three of the new analogues are better isosteres of bzbr that contain bulky groups adjacent to the phenol and have increased pK(a) values. These ligands test the hypothesis that anionic substrates bind with higher affinity to 2C9. Since they have higher affinity than the previous nonacidic analogues, the importance of bulky groups on the phenol ring appears to have been underestimated. CoMSIA models predict that these bulky groups are favorable for their hydrophobicity, while a negative charge is favored at the ketone oxygen rather than the phenol oxygen. The overlap of this ketone with electronegative groups of other 2C9 substrates suggests they act as key positive charge acceptors.

A new class of CYP2C9 inhibitors: probing 2C9 specificity with high-affinity benzbromarone derivatives.

Noncovalent forces, other than hydrophobic interactions, are important determinants of substrate bias exhibited by some cytochromes P450. The CYP2C9 pharmacophore is proposed to include either an anionic group or hydrogen bond donor in addition to its hydrophobic groups. By constructing analogs of benzbromarone, evidence supporting the existence of a 2C9 anion-binding site was revealed. A nonsubstituted phenol analog was determined to have a pKa of 8.4 and a Ki of 414 nM whereas those with dihalogenated benzoyl phenols had pKa values between 4.2 to 5.2 and Ki values as low as 1 nM. The nonhalogenated, nonionizable analog is the poorest binder at 796 nM. The Ki range covers around three orders of magnitude with even the weakest binder being a more potent inhibitor than 2C9 substrate phenytoin. Thus, benzbromarone derivatives represent a class of molecules with the potential to reveal more structural details of the 2C9 active site.