Design, Synthesis And Biological Evaluation Of Novel Diarylpyridine Derivatives As HIV-1 NNRTIs

Acquired immune deficiency syndrome (AIDS), mainly caused by human immunodeficiency virus type-1 (HIV-1) is still a prevalent disease worldwide. The most common and effective treatment of AIDS is the highly active antiretroviral therapy (HAART). Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are important components of HAART with high antiviral potency, high specificity and low cytotoxicity. Even so, a major problem is that the long-term efficacy of NNRTIs is limited by the rapid emergence of drug-resistant variants of HIV-1. Hence, the development of novel chemical entities with high affinity for the mutated RT has been a very active research field in recent yearsPrompted by the structure-activity relationships of DAP Y and the analyses of the crystal structures of DAPY/RT, a series of novel 2-aminodiarylpyridine derivates were designed. The central pyrimidine of DAPY was replaced by pyridine according to the bioisosterism. The 4-cyano-aniline remain unchanged, extending to the region surrounded by Leu234 and Pro236. NH2 was introduced to the pyridine, forming H-bonds with K101 or K103. The linker between left ring and pyridine is O or N.The NNIBP entrance channel is a large open region in front of Lys103, Glu188 and Vall 79. The modification of NNRTIs with solubilizing substituents, which extend into entrance channel is an effective strategy for developing novel inhibitors with improved pharmacological properties. Prompted by the analyses of the crystallographic overlay of TMC125 and 7e, the novel diarylpyridine scaffold was created using crystallographic overlays based molecular hybridization. The preferred combination of the trisubstituted phenoxy ring, the para-cyanoaniline moiety, and the NH group of DAPYs were preserved. Substituents at the 2-carboxamide nitrogen in the IASs series were introduced to further improve the interaction with the entrance channel.The activity results of diarylpyridine derivates indicated that the existing of π-electron (prop-2-yn-1-yl and allyl) is a key chemical feature responsible for the exceptional biological activities of the compounds against the mutant HTV-1 strain, B-5b5 is active against WT and the K103N+Y181C resistant mutant HIV-1 with EC50 values of 29 nM and 6.1 μM. Also promoted by the indolylarylsulfones carrying a heterocyclic tail, the novel triazole diarylpyridine derivates were designed, triazole containingπ-electrons were introduced by click chemistry extending to the NNIBP entrance channel.The synthetic work started with the commercially available 3-amino-5-bromopyridine and diethyl 1,3-acetoriedicarboxylate. 3-amino-5-bromopyridine was acylated, nitrificated and hydrolyzed, affording 5-bromo-2-nitropyridin-3-amine. Intermediate A-4 was obtained by Buchwald-Hartwig reaction with 4-aminobenzonitrile. Reaction of A-4 with PhOH or PhNH2 by Ullmann reaction or Buchwald-Hartwig reaction, affording A-5a1-10 and A-5b1-2. Reduction of A-5a with SnCl2, affording A-6a1-9. Reaction of diethyl 1,3-acetonedicarboxylate with triethyl orthoformate in acetic anhydride, followed by cyclisation with ammonia, resulted in formation of ethyl 4,6-dihydroxynicotinate (B-1). Treatment of B-1 with phosphorus oxychloride gave ethyl 4,6-dichloronicotinate, which underwent nucleophilic substitution reaction with phenols under conditions of DMF/K2CO3, then reaction with 4-aminobenzonitrile by Buchwald-Hartwig coupling. The final derivatives B-5a1-11 and B-5b1-11 were obtained by ammonolysis of intermediate B-4a and B-4b using trimethylaluminium. Triazole diarylpyridine derivates C-3a1-14 and C-3b1-9 were obtained by Click chemistry with B-5b5.The newly synthesized compounds were evaluated for their activity against HIV and tested in enzymatic assays against HIV-1 RT. Most of the 2-aminodiarylpyridine derivates were found to be active against wild-type HIV-1 with an EC50 in the range of 0.04-4.41 μM. A-5b2 (EC50= 0.042μM, SI= 3963) were identified as the most potent inhibitors, which were more potent than the reference drugs nevirapine. The biological assay results clearly indicated that the activities of the compounds where X is NH are generally better than the compounds where X is O. The enzymatic activity and SARs of the 2-aminodiarylpyridine compounds is in line with the results of the cellular tests. Compound A-6a3 (IC50= 52 nM) exhibited the highest enzymatic inhibition activity, which is equal to that of efavirenz and 45 times higher than that of nevirapine.Most of the new diarylnicotinamide derivates were found to be active against wild-type HIV-1 with an EC50 in the range of 0.027-4.54 μM. Among them, compound B-5b11 (EC50= 0.027 μM, SI> 12518) and B-5b5 (EC50= 0.029 μM, SI= 2471) were identified as the most potent inhibitors, which were more potent than the reference drugs nevirapine and delavirdine. Some diarylnicotinamide derivates were also active at micromolar concentrations against the K103N+Y181C resistant mutant. Among the N-substituted amides, the optimum activities were found in compounds with substituents containing a π-electron character. Prop-2-yn-1-yl appeared to be the most favorable group, closely followed by N-substituents in the sequence prop-2-yn-1-yl> allyl,2-cyanoethyl. However, bulky substitutions such as 2-(dimethylamino)ethyl or 2,2-dimethoxyethyl at this position led to significant loss of antiviral potency compared to other analogues in each series. Besides, it is worth noting that the introduction of a hydrophobic ring group may impair the activity. The enzymatic activity and SARs of these compounds is in line with the results of the cellular tests. Compound B-5b11 (IC50= 20 nM) exhibited the highest enzymatic inhibition activity, which is equal to that of efavirenz and 31 times higher than that of nevirapine. It is reasonable that the newly synthesized diarylnicotinamide derivates can specifically target HIV-1 RT.The activy of triazole diarylpyridine derivates is being tested.Taken in sum, through the bioisosterism and crystallographic overlays based molecular hybridization approach, three series of novel diaryllpyridine derivates were designed. All the synthesized compounds were identified by MS,’H-NMR and 13C-NMR. The newly synthesized compounds were evaluated for their activity against HIV and tested in enzymatic assays against HIV-1 RT. The SAR analysis provides valuable information for the future structure optimization of novel HIV-1 NNRTIs.