Exploring Long Arm Amide-Linked Side Chains in the Design of Antifungal Azole Inhibitors of Sterol 14α-Demethylase (CYP51)

The rise in fungal drug resistance has exacerbated the treatment of invasive fungal infections, most commonly caused by <i>Candida</i>. This research describes the synthesis of extended "long-arm" azole antifungals that were evaluated against wild-type and resistant fungal species. Biphenyl derivative <b>22</b> was the most effective derivative, displaying potent inhibitory activity against <i>Saccharomyces</i>, <i>Candida</i>, and <i>Cryptococcus</i> CYP51 enzymes, including in resistant strains, in comparison with posaconazole. The X-ray crystal structure of <i>S</i>-<b>22</b> complexed with <i><i>S. cerevisiae</i></i> CYP51 showed a hydrogen bond between the oxygen of the trifluoromethoxy group of <i>S-</i><b>22</b> and the His381 side chain of <i><i>S. cerevisiae</i></i> CYP51, which is postulated to contribute significantly to its binding, and stabilization in the presence of the <i><i>S. cerevisiae</i></i> CYP51 Y140F/H, <i>C. parapsilosis</i> and <i>C. auris</i> CYP51 Y132F mutations and the <i>C. auris</i> K143R mutation. Computational studies and IC₅₀ evaluation of compound <b>22</b> vs <i><i>C. albicans</i></i> wild-type, Y132F, and Y132H/K143 mutant strains supported MIC observations.