2H-Pyrrolo[3,4-b] [1,5]benzothiazepine derivatives as potential inhibitors of HIV-1 reverse transcriptase

A number of 2H-pyrrolo[3,4-b] [1,5]benzothiazepine derivatives (PBTAs) 7–25 and the related synthetic intermediates 3-pyrrolyl aryl sulfones (PASs) 26–32 were designed, synthesized and tested as potential anti-HIV-1 agents targeted at the reverse transcriptase (RT). The PBTAs were conceived as tricyclic analogs of nevirapine, pyrrolo[1,2-b] [1,2,5]benzothiadiazepine 5 (PBTD) and pyrrolo[2,1-d] [1,2,5]benzothiadiazepine 6, NNRTIs endowed with potent anti-HIV-1 activities. The majority of tested PBTAs were active against HIV-1-induced cytopathicity in MT-4 cells at concentrations ranging from 0.3 to 40 μM. In particular, compound 10 was the most potent derivative with EC₅₀ = 0.3 μM, comparable to that of nevirapine used as reference drug. In the 3-pyrrolyl aryl sulfones (26–32) series only three sulfones were found active against HIV-1 replication cycle. The following preliminary SAR could be depicted for the title derivatives: i) the conformationally restrained PBTAs are more potent than the corresponding open counterparts (PASs); ii) the DMA group give the highest anti-HIV-1 potency in the PBTAs series; iii) PBTAs and the corresponding thiones are equipotent; iv) an unsubstituted amino group, as part of p-chloroanilino moiety, is a strong determinant for the antiviral activity in the PASs series. The most potent derivatives in cell-based assays were proven to target the RT in enzyme assays. Unfortunately, none of the test compounds inhibited the multiplication of clinically relevant drug-resistant viruses (mutants of HIV-1 carrying K103N and Y181C mutations) at concentrations lower than 30 μM. However, the good results obtained against replication of wt HIV-1, lead us to consider compound 10 as a lead compound for further investigation in this field. In particular, our efforts will be directed to modifications of 10 devoted to obtain new derivatives active against HIV-1 mutant strains.