Tetra-chloro-(bis-(3,5-dimethylpyrazolyl)methane)gold(III) chloride: An HIV-1 reverse transcriptase and protease inhibitor

The title compound ([3,5-Me₂bpzaH₂][AuCl₄]Cl, 1) (Me₂bpza = bis(3,5-dimethylpyrazolyl)acetic acid), was prepared by reacting H[AuCl₄] with 3,5-Me₂bpza; and spectroscopically and structurally characterized. In the solid state structure of 1, the pyrazolyl ligand is doubly protonated to form two strong charge assisted hydrogen bonds of the type N⁺{single bond}H⋯Cl^- with the single chloride anion whilst the [AuCl₄]^- anion remains discrete. The anti-HIV-1 activity of 1 was determined by a colorimetric direct enzyme reverse transcriptase (RT) assay and a fluorogenic protease (PR) assay. Compound 1 significantly (p < 0.05) inhibited RT over a concentration range of 5-250 μM and inhibited HIV-1 protease at 100 μM. Compound 1 inhibited two very important HIV-1 enzymes (RT and PR) in direct enzyme assays and therefore warrants further evaluation.