Design, synthesis and evaluation of novel anti-HCV molecules that deliver intracellularly three highly potent NS5A inhibitors

Abstract

The design and synthesis of new non-symmetrical NS5A inhibitors with sulfur containing amino acids is reported along with their ability to block HCV replication in an HCV 1b replicon system. These compounds display EC50 values in the picomolar range with a large therapeutic index (>10(6)). Moreover, cellular pharmacology studies show that our preferred compounds intracellularly deliver three potent NS5A inhibitors.

Keywords: Antiviral; HCV; NS5A.

Figure 1

Structures of BMS-790052, ABT-267 and GS-5885.

Figure 2

Delivery of three active molecules intracellularly.

Figure 3

Predicted binding of compounds 8c (a), 9 (b) and 10 (c) to Site-2 of NS5A associated with GT1b activity. NS5A dimer: chain A- gold ribbon and atoms; chain B- blue ribbon and atoms. Residues within 4.5Å of the inhibitor are displayed. a) Force field minimized analog 8c, with CH₂SBn substitution, forms favorable packing interactions with R30, L31, and Y161 (blue arrow) of Site-2 consistent with low picomolar activity. b) CH₂SOBn substitution of the minimized analog 9 (R) isomer is thought to reduced potency by destabilizing Bn packing with aromatic Y161 (orange arrow) c) Minimized analog 10, with CH₂SO₂Bn substitution, has restored predicted interactions with Y161 of WT receptor and similar potency to 8c.

Figure 4

Energy minimized binding of sulfone 10 in a two site model provides a structural rational for potent anti-HCV activity

Scheme 1

Reagents and conditions: (a) ClCOOMe, NaOH 1 M, Na₂CO₃, 0 °C – rt, 18 h, 41-68%.

Scheme 2

Reagents and conditions: (a) Br₂, CH₂Cl₂, rt, overnight, 85%; (b) (i) Boc-L-Proline, DIPEA, rt, 5 h; (ii) NH₄OAc, toluene, 130 °C, 4 h, 79%; (c) 6 N HCl, CH₃OH, 50 °C, 5 h, 89%; (d) N-methoxycarbonyl-L-Valine, EDC, HOBt, DIPEA, CH₃CN, 0 °C – rt, 3 h, 40%; (e) 2a-d, EDC, HOBt, DIPEA, CH₃CN, 0 °C – rt, 3 h, 35-51%.

Scheme 3

Reagents and conditions: (a) NaIO₄, MeOH/H₂O, rt, 3 h, 71%; (b) H₂O₂, Na₂WO₄.2H₂O, BnN(Et)₃Cl, 3 h, 49%;