To evaluate the inhibition of Hsp90 dimerization, E. coli BL21 (DE3) pETSH-3 cells were used to display Hsp90α on their surface (Figure ). Passenger-driven dimer formation of Hsp90α is facilitated through the motility of the β-barrel domain within the outer membrane of E. coli, as reported for other proteins. To demonstrate the functionality of dimerized Hsp90 on the surface of E. coli, the transcription factor p53, a natural client protein of Hsp90, was labeled with fluorescein isothiocyanate (FITC) and added to cells displaying Hsp90 on their surface. Subsequent flow cytometer analysis revealed a high green fluorescence for cells displaying Hsp90, indicating dimerized and functional Hsp90 (Figure ). Compounds 5a, 6, and 7a showed only weak inhibition of 3.27 %, 14.65 %, and 24.35 %, respectively. In contrast, 5b, 5c, 5d, and 7b showed moderate inhibition of 39.92 %, 41.83 %, 55.23 %, and 31.33 %, respectively (Figure ).