Symmetric benzidine derivatives as anti-HCV agents: Insight into the nature, stereochemistry of the capping amino acid and the size of the terminal capping carbamates

Novel symmetric molecules, bearing a benzidine prolinamide core, two terminal carbamate caps of variable sizes and nature, including natural and unnatural Amino acids were developed. Several terminal N-carbamate substituents of the core structure, ranging from linear methyl, ethyl and butyl groups to branching isobutyl group; and an aromatic substituent were also synthesized. Series 1 has hydrophobic AA residues, namely S and R phenylglycine and a terminal carbamate capping group, whereas Series 2 bears sulphur containing Amino acids, specifically S and R methionine and the natural R methylcysteine. The novel compounds were tested for their inhibitory activity (EC₅₀) and their cytotoxicity (CC₅₀), using an HCV 1b (Con1) reporter replicon cell line. Compound 4 with the unnatural capping residue, bearing d-Phenylglycine amino acid residue and N-isobutyloxycarbonyl capping group, was the most active within the two series, with EC₅₀ = 0.0067 nM. Moreover, it showed high SI₅₀ > 14788524 and was not cytotoxic at the highest tested concentration (100 μΜ), indicating its safety profile. Compound 4 also inhibited HCV genotypes 2a, 3a and 4a. Compared to the clinically approved NS5A inhibitor Daclatasvir, compound 4 shows higher activity against genotypes 1b and 3a, as well as improved safety profile.