A NOVEL CONSTRAINED REDUCED-AMIDE INHIBITOR OF HIV-1 PROTEASE DERIVED FROM THE SEQUENTIAL INCORPORATION OF GAMMA-TURN MIMETICS INTO A MODEL SUBSTRATE

C7 mimetics, designed to lock three amino acid residues of a peptide chain into a gamma-turn conformation, were introduced sequentially between the P3 to P2' positions of a model HIV-1 protease substrate I (resulting in compounds II-IV) to probe its conformational requirements in binding to HIV-1 protease. Of these, compound IIIa with the C7 Mimetic replacing Asn-Tyr-Pro, corresponding to the P2 through P1' positions of substrate, was found to be an inhibitor with a K(i) of 147 muM. Reduction of the amide bond in the C7 mimetic of IIIa resulted in a novel constrained reduced-amide mimetic VIa with a K(i) of 430 nM. This corresponds to over a 300-fold improvement in inhibitory activity over the original C7 mimetic. The inhibitory activity of mimetic VIa was in addition found to be 44-fold better than a similar linear reduced-amide containing inhibitor V. The synthesis of these mimetics are described.