Optimization of Hsp90/Aha1 Small-Molecule Disruptors Via the Evaluation of Amide Bioisosteres

Recent structure-activity relationships (SAR) were established around KU-177, the parent scaffold for an Hsp90/Aha1 small-molecule disruptor, which suggested that the central amide linker adopted a <i>cis</i>-amide conformation for the inhibitory activity. In this Letter, a series of analogues was synthesized to contain various amide bioisosteres, which were evaluated for their ability to disrupt Hsp90/Aha1 interactions. The inhibitory activity was determined with recombinant protein as well as co-immunoprecipitation experiments with cell lysates. The most efficacious scaffolds were assessed for solubility, metabolic stability, and permeability, where the most efficacious molecule was the sulfonamide-containing compound <b>44</b>. New molecules emerged from this study and will be optimized in subsequent SAR campaigns.