Synthesis and structure-activity relationship studies of HIV-1 virion infectivity factor (Vif) inhibitors that block viral replication

Abstract

The human immunodeficiency virus 1 (HIV-1) virion infectivity factor (Vif) protein, essential for in vivo viral replication, protects the virus from innate antiviral cellular factor apolipoprotein B mRNA-editing, enzyme-catalytic, polypeptide-like 3G (APOBEC3G; A3G) and is an attractive target for the development of novel antiviral therapeutics. We have evaluated the structure-activity relationships of N-(2-methoxyphenyl)-2-((4-nitrophenyl)thio)benzamide (RN-18), a small molecule recently identified as an inhibitor of Vif function that blocks viral replication only in nonpermissive cells expressing A3G, by inhibiting Vif-A3G interactions. Microwave-assisted cross-coupling reactions were developed to prepare a series of RN18 analogues with diverse linkages and substitutions on the phenyl rings. A dual cell-based assay system was used to assess antiviral activity against wild-type HIV-1 in both nonpermissive (H9) and permissive (MT4) cells that also allowed evaluation of specificity. In general, variations of phenyl substitutions were detrimental to antiviral potency and specificity, but isosteric replacements of amide and ether linkages were relatively well tolerated. These structure-activity relationship data define structural requirements for Vif-specific activity, identify new compounds with improved antiviral potency and specificity, and provide leads for further exploration to develop new antiviral therapeutics.

Figure 1

Chemical Structures of HIV-1 Vif Inhibitors RN18 and RN19.

Figure 2

a) A convergent route for the synthesis of RN18 and analogues; b) alternate route for the synthesis of RN18 and C-ring analogues.

Scheme 1

Reagents and conditions: a) Cu(I)I, K₂CO₃, iPrOH, HOCH₂CH₂OH, MW (150 WT), 80 °C, 30 min (2 ×); b) SnCl₂∙2H₂O, EtOAc, 80 °C, 3 h.

Scheme 2

Reagents and conditions: a) Cu(I)I, K₂CO₃, 1,2-DME, MW (150 WT), 80 °C, 30 min (2 ×); (b) Ba(OH)₂∙8H₂O, MeOH, 80 °C, 2 h; (c) (i) (COCl)₂, CH₂Cl₂, DMF, RT, 8 h, (ii) R′R″NH (14a–h), Et₃N, CH₂Cl₂, 0 °C to RT, overnight; d) SnCl₂∙2H₂O, EtOAc, 80 °C, 3 h.

Scheme 5

Reagents and conditions: (a) Cu(I)Cl, Cs₂CO₃, CH₂(Cot-Bu)₂, NMP, MW (150 WT), 120 °C, 30 min (2 ×); b) Cu(OAc)₂, CH₂Cl₂, PhOH, Et₃N, 4A MS, RT, overnight; c) K₂CO₃, DMF, MW (150 WT), 90 °C, 30 min (2 ×).