Design, Synthesis And Bioactivity Evaluation Of Novel Substituted 1, 2, 4-Triazole Derivatives As HIV-1 NNRTIs

Human immunodefeciency virus type 1(HIV-1)is the etiologic agent responsible for the onset of the acquired immunodeficiency syndrome(AIDS).HIV-1 is a retrovirus which encodes a reverse transcriptase(RT)that is required for viral replication.RT is responsible for the conversion of the single-stranded RNA viral genome into double-stranded DNA that subsequently integrates into the host DNA.Because of the crucial function of RT in the HIV-1 life cycle,it becomes one of the important targets of antiviral therapy.Non-nucleoside reverse transcriptase inhibitors(NNRTIs),which inhibit the enzyme by an non-competitively allosteric mechanism involving binding to a hydrophobic pocket adjacent to the substrate (dNTP)binding site of the enzyme and inducing the conformation alteration of RT, thereby to inhibit the enzymatic function of RT.NNRTIs have chemical diversity which are significant component of highly active antiretroviral therapy(HAART). The need for novel NNRTIs active against drug-resistant mutants selected by current therapies is of paramount importance.On the basis of the general crystal structure of the HIV-1 RT complexed with NNRTIs,and accord to the general principle of bioisosteric replacement which is a strategy of medicinal chemistry for the rational design of new drugs applied with a lead compound as a special process of molecular modification,we screened 4-arylideneamino-5-alkylthio derivative of 4-amino-3-(2'-furyl)-5-mercapto-4H-1, 2,4-triazole 4e,a new class of specific NNRTI,as lead compound.Furthermore consulted to the structure-activity relationship(SAR)and crystal structure of 4-benzyl-3-thienyl-5-mercapto-4H-1,2,4-triazole derivatives,we designed a series of novel 4-arylideneamino-5-alkylthio derivatives of 4-amino-3-(2'-thienyl)-5-mercapto-4H-1, 2,4-triazole(a)which possess potent anti-HIV-1 activity of the NNRTIs.The target molecules evaluated with docking program of virtual screening were synthesized.From high-throughput screening(HTS)of compounds library,several sulfanyltriazole/sulfanyltetrazole-typed leads were identified as novel NNRTIs,which have simple,yet distinctively different chemical structure from the HIV inhibitors reported in the literature.Extensive structural modification and bioactivity research demonstrated that most of them showed significant activity in vitro on the WT or K103N-Y181C HIV-1 RT.Based on extensive SAR and molecular modeling studies of sulfanyltriazole/sulfanyltetrazole-typed NNRTIs,consulted to the crystal structure of Capravirine at the same time,the structures of derivatives of sulfanyltriazole/ sulfanyltetrazole-typed and Capravirine inhibitors were analyzed with DiscoTECH module of Sybyl 7.0 to built up an efficient pharmacore model.On the basis of the pharmacore model,we reformed a series of derivatives of sulfanyltriazole(b).For the preparation of the newly designed molecules,target compounds 10a1-25 were from an one-pot reaction to prepare 4-amino-3-(2'-furyl/thienyl) -5-mercapto-1,2,4-triazole,which came from the reaction of 2-furyl/thienyl acid hydrazide with excess hydrazine,then the triazole core was synthesized by condensation with aromatic aldehydes to afford Schiff's bases and further alkylation with benzyl halides.For compounds 8b1-14,we chose isobutyric acid as the starting material,after esterification,hydrazinolysis,addition reaction with different isothiocyanates,then cyclo-condensation with excess hydroxide and finally,the alkylating reaction at the 5-mercapto.Totally,39 novel compounds have been synthesized.Their structures were identified by MS,¹H-NMR,¹³C-NMR and IR spectral analysis respectively.The preliminary activity and cytotoxicity screening of the newly designed and synthesized 4-amino-3-(2'-furyl/thienyl)-5-mercapto-4H-1,2,4-triazole derivatives 10a1-25 and sulfanyltriazole derivatives 8b1-9 were tested in MT-4 cells for inhibition of HIV-1.The screening results indicate that many compounds exhibit inhibition activity of HIV-1.Among the evaluated compounds,N-(2-nitrophenyl) -2-(4-(2-fluorobenzyl)-3-isopropyl-4H-1,2,4-triazol-5-ylthio)acetamide(8b4) emerges as the most active HIV-1 inhibitor with EC₅₀=4.26μM and CC₅₀=209μM, SI=49,which provides useful information for further investigation of 1,2,4-triazole based NNRTIs.Moreover,the anti-viral activity assay of the newly synthesized derivatives of sulfanyltriazole 8b10-14 is in progress,from which we are expecting that we may get some useful things.In summary,we designed and synthesized 2 series of novel compounds,which were designed and synthesized according to hybrid approach,bioisosterism principle, taking the 4-amino-5-mercapto-4H-1,2,4-triazole and sulfanyltriazole/ sulfanyltetrazole-typed NNRTIs as leads.Through biological evaluation,we find some potent anti-HIV agents,which is worth further investigation and development.