Reduction of Peptide Character of HIV Protease Inhibitors That Exhibit Nanomolar Potency against Multidrug Resistant HIV-1 Strains

Novel HIV protease inhibitors containing a hydroxyethylamine dipeptide isostere as a transition state-mimic king structure were synthesized by combining substructures of known HIV protease inhibitors. Among them, TYA5 and TYB5 were proven to be not only potent enzyme inhibitors (<i>K</i><sub>i</sub> = 0.12 nM and 0.10 nM, respectively) but also strong anti-HIV agents (IC<sub>50</sub> = 9.5 nM and 66 nM, respectively), even against viral strains with multidrug resistance. Furthermore, insertion of an (<i>E</i>)-alkene dipeptide isostere at the P<sub>1</sub>−P<sub>2</sub> position of TYB5 led to development of a purely nonpeptidic protease inhibitor, TYB1 (<i>K</i><sub>i</sub> = 0.38 nM, IC<sub>50</sub> = 160 nM).