Protein–protein interactions (PPIs) regulate all signaling pathways for cellular function. Developing molecules that modulate PPIs through the interface of their protein surfaces has been a significant challenge and there has been little success controlling PPIs through standard molecular library screening approaches. PPIs control the cell’s protein-folding machinery, and this machinery relies on a multiprotein complex formed with heat shock protein 70 (Hsp70). Described is the design, synthesis, and biological evaluation of molecules aimed to regulate the interaction between two proteins that are critical to the protein-folding machinery: heat shock protein 70 (Hsp70) and cochaperone heat shock organizing protein (HOP). We report the first class of compounds that directly regulate these two protein–protein interactions and inhibit protein folding events.