Gabriella Collu

Antiviral and cytotoxic activities of aminoarylazo compounds and aryltriazene derivatives

Abstract Twelve aminoarylazocompounds (A–C) and 46 aryltriazene 7 derivatives (D–G) have been synthesized and evaluated in cell-based assays for cytotoxicity and antiviral activity against a panel of 10 RNA and DNA viruses. Eight aminoazocompounds and 27 aryltriazene derivatives exhibited antiviral activity, sometimes of high level, against one or more viruses. A marked activity against BVDV and YFV was prevailing among the former compounds, while the latter type of compounds affected mainly CVB-2 and RSV. None of the active compounds inhibited the multiplication of HIV-1, VSV and VV. Arranged in order of decreasing potency and selectivity versus the host cell lines, the best compounds are the following; BVDV: 1 > 7 > 8 > 4; YFV: 7 > 5; CVB-2: 25 > 56 > 18; RSV: 14 > 20 > 55 > 38 > 18 > 19; HSV-1: 2. For these compounds the EC50 ranged from 1.6μM (1) to 12μM (18), and the S. I. from 19.4 (1) to 4.2 (2). Thus the aminoarylazo and aryltriazene substructures appear as interesting molecular component for developing antiviral agents against ss RNA viruses, particularly against RSV and BVDV, which are important human and veterinary pathogens. Finally, molecular modeling investigations indicated that compounds of structure A–C, active against BVDV, could work targeting the viral RNA-dependent RNA-polymerase (RdRp), having been observed a good agreement between the trends of the estimated IC50 and the experimental EC50 values.

Synthesis and in vitro evaluation of the anti-viral activity of N-[4-(1H(2H)-benzotriazol-1(2)-yl)phenyl]alkylcarboxamides

A series N-[4-(1H(2H)-benzotriazol-1(2)-yl)phenyl]alkylcarboxamides (8e-k, 9e-i, k, l) and their parent amines (5a-c and 6a-d) were prepared according to Schemes (1 and 2). Compounds were evaluated in vitro for cytotoxicity and antiviral activity against a wide spectrum of RNA (positive- and negative-sense) viruses, like [Bovine Viral Diarrhea Virus (BVDV), Yellow Fever Virus (YFV), Coxsackie Virus B (CVB-2), Polio Virus (Sb-1), Human Immunodeficiency Virus (HIV-1), Respiratory Syncytial Virus (RSV)] or double-stranded (dsRNA) virus, like Reoviridae (Reo-1). The Entero (CVB-2 and Sb-1) were the only viruses inhibited by title compounds. In particular, two of them emerged for their selective, although not very potent, antiviral activity: 8i, which was the most active against CVB-2 (CC50 >100 microM; EC50 = 10 microM) and 9l, which was the most active against Sb-1 (CC50 90 microM; EC50 = 30 microm). Title compounds were evaluated in silico against the Sb-1 helicase, as the crystal structure of this enzyme was not available, the corresponding 3D model was obtained by homology techniques (see Fig. 2).

Novel modifications in the series of O-(2-phthalimidoethyl)-N-substituted thiocarbamates and their ring-opened congeners as non-nucleoside HIV-1 reverse transcriptase inhibitors

The structure-activity relationships (SARs) of N-aryl-O-(2-phthalimidoethyl)thiocarbamates (C-TCs) and their imide ring-opened congeners (O-TCs) as non-nucleoside HIV-1 reverse transcriptase inhibitors were further investigated. The SAR strategy involved modifications of the N-phenyl ring followed by the hybridization of the most promising N-aryl and O-(2-phthalimidoethyl) substructures. The role of stereochemistry and tert-butyl substitution of the phthalimidoethyl moiety on activity was also investigated. Seventy-six analogues were prepared by parallel solution-phase synthesis. Twenty-two C-TCs displayed nanomolar activity against wild-type HIV-1 and a number of analogues were effective against the Y181C mutant. Compound 56 combined the highest activity so far identified against Y181C (EC(50)=1.3 microM) with good potency against the K103R mutant (EC(50)=4.8 microM). Docking simulations helped to rationalize the SARs.

Synthesis of variously substituted 3-phenoxymethyl quinoxalin-2-ones and quinoxalines capable to potentiate in vitro the antiproliferative activity of anticancer drugs in multi-drug resistant cell lines.

Two series of 1,6-dimethyl-3-phenoxymethylquinoxalin-2-ones and 1-benzyl-3-phenoxymethyl-7-trifluoromethylquinoxalin-2-ones, and a series of 2-benzyloxy-3-phenoxymethyl-7-trifluoromethylquinoxaline were synthesized. Their capability to restore/potentiate the antiproliferative activity of clinically useful drugs, such as doxorubicin (Doxo), vincristine (VCR) and etoposide (VP16), in drug-resistant human nasopharyngeal carcinoma KB cells (KB(WT), KB(MDR), KB(7D)and KB(V20C)) was evaluated. In vitro data show that many quinoxalin-2-ones and quinoxalines potentiate the antiproliferative activity of Doxo and VCR in tumor-derived MDR cell lines. In this series, 17a turned out to be the most potent quinoxaline derivative in potentiating the antiproliferative activity of doxorubicin and vincristine against KB(MDR) and KB(V20C) resistant cell lines, respectively.

Synthesis of Novel Uracil Non‐Nucleoside Derivatives as Potential Reverse Transcriptase Inhibitors of HIV‐1

Novel emivirine and TNK‐651 analogues 5a–d were synthesized by reaction of chloromethyl ethyl ether and / or benzyl chloromethyl ether, respectively, with uracils having 5‐ethyl and 6‐(4‐methylbenzyl) or 6‐(3,4‐dimethoxybenzyl) substituents. A series of new uracil non‐nucleosides substituted at N‐1 with cyclopropylmethyloxymethyl 9a–d, 2‐phenylethyloxymethyl 9e–h, and 3‐phenylprop‐1‐yloxymethyl 9i–l were prepared on treatment of the corresponding uracils with the appropriate acetals 8a–c. Some of the tested compounds showed good activity against HIV‐1 wild type. Among them, 1‐cyclopropylmethyloxymethyl‐5‐ethyl‐6‐(3,5‐dimethylbenzyl)uracil 9c and 5‐ethyl‐6‐(3,5‐dimethylbenzyl)‐1‐(2‐phenylethyloxymethyl)uracil 9g showed inhibitory potency equally to emivirine against HIV‐1 wild type. Furthermore, compounds 9c and 9g showed marginal better activity against NNRTI resistant mutants than emivirine.

Parallel synthesis, molecular modelling and further structure–activity relationship studies of new acylthiocarbamates as potent non-nucleoside HIV-1 reverse transcriptase inhibitors

The structure-activity relationships (SARs) of acylthiocarbamates (ATCs), a new class of non-nucleoside HIV-1 reverse transcriptase inhibitors, have been expanded. Sixty-six new analogues were prepared by parallel solution-phase synthesis. In general, the potency of new ATCs was better than that of the first series and O-[2-phthalimidoethyl] 4-chlorophenyl(3-nitrobenzoyl) thiocarbamate turned out to be the most potent ATC so far synthesized (EC(50)=1.5nM). Several ATCs were active at micromolar concentrations against HIV-1 strains carrying the RT Y181C mutation and one of them was also moderately active against the K103R variant. Docking simulations were carried out to rationalize the most relevant SARs.

Synthesis of Novel Fluoro Analogues of MKC442 as Microbicides

Novel analogues of MKC442 (6-benzyl-1-(ethoxymethyl)-5-isopropylpyrimidine-2,4(1H,3H)-dione) were synthesized by reaction of 6-[(3,5-dimethylphenyl)fluoromethyl]-5-ethyluracil (5) with ethoxymethyl chloride and formaldehyde acetals. The Sonogashira reaction was carried out on the N1-(p-iodobenzyl)oxy]methyl derivative of compound 5 using propagyl alcohol to afford compound 12 (YML220). The latter compound was selected for further studies since it showed the most potent and selective activity in vitro against wild-type HIV-1 and non-nucleoside reverse transcriptase inhibitor-, nucleoside reverse transcriptase inhibitor-, and protease inhibitor-resistant mutants and a wide range of HIV-1 clinical isolates. 12 also showed microbicidal activity in long-term assays with heavily infected MT-4 cells.

A Novel Synthetic Route for the Anti‐HIV Drug MC‐1220 and its Analogues

The HIV pandemic continues to spread throughout the world, particularly affecting populations in developing countries. Efforts to limit this scourge need to be maximally implemented. Women now account for the majority of HIV-infected people worldwide, indicating the need for products that allow women the option of self-protection from HIV transmission without the knowledge of their sexual partners. The concepts of vaginal microbicides are a potentially promising strategy to prevent the spread of HIV. Microbicides are self-administered, prophylactic products designed to protect against sexually transmitted pathogens, including HIV-1. A special subgroup of NNRTIs, the dihydroalkoxybenzyloxopyrimidines (DABOs), have a proven capacity to irreversibly block HIV-1 replication. [7–10] This property correlates with their ability to bind HIV-1 RT with high affinity. One of the most important lead compounds of this series of tight-binding NNRTIs is MC-1220, which is used in racemic form. [11, 12] The synthesis of

Thiocarbamates as non-nucleoside HIV-1 reverse transcriptase inhibitors. Part 2: Parallel synthesis, molecular modelling and structure–activity relationship studies on analogues of O-(2-phenylethyl)-N-phenylthiocarbamate

To acquire further insight into the structure-activity relationship (SAR) of the thiocarbamates (TCs) described in the preceding work, 57 analogues of the lead compound O-(2-phenylethyl)-N-phenylthiocarbamate I were prepared by parallel solution-phase synthesis. We varied the 2-phenylethyl moiety (mono-substitution on the phenyl ring and modification of the ethyl linker), keeping constant the N-phenyl ring substitutions which have given the best results in the previous series. Most of the new TCs inhibited wild-type HIV-1 at micro- and nanomolar concentrations in MT-4 cell-based assays. Some TCs were also active at micromolar concentrations against the Y181C and/or K103N/Y181C resistant mutants. The SARs were rationalized by docking simulations.

Parallel one-pot synthesis and structure–activity relationship study of symmetric formimidoester disulfides as a novel class of potent non-nucleoside HIV-1 reverse transcriptase inhibitors

The molecular duplication of non-nucleoside reverse transcriptase inhibitor (NNRTI) O-(2-phthalimidoethyl)-N-arylthiocarbamates (C-TCs) led to the identification of symmetric formimidoester disulfides (DSs) as a novel class of potent NNRTIs. The lead compound 1 [dimer of the isothiocarbamic form of TC O-(2-phthalimidoethyl)-N-phenylthiocarbamate] turned out to prevent the wild-type HIV-1 multiplication in MT-4 cell culture with an EC(50) value of 0.35 microM. In order to perform a structure-activity relationship (SAR) study, we prepared 40 analogues of 1 by an unprecedented one-pot method of solution-phase parallel synthesis. The SAR strategy was focused on the variation of the N-aryl portion (mono-, di- and trisubstitution of the phenyl ring and its replacement with a 1-naphthyl, cyclopropyl or benzyl group) and of the 2-phthalimidoethyl moiety (introduction of a methyl on the phthalimide substructure, replacement of the phthalimide moiety with a phenyl ring and elongation of the ethyl linker). Most DSs proved to inhibit the wild-type HIV-1 replication in cell-based assays and 15 of them were active at nanomolar concentrations. The most potent congeners (11, 15, 16, 17, 18, 19, 20 and 32, EC(50): 10-70 nM) shared the N-para-substituted phenyl moiety. Compound 17 tested in enzyme assay against recombinant wild-type reverse transcriptase displayed an IC(50) value of 0.74 microM. Compounds 19 and 33 were active at micromolar concentrations against the clinically relevant Y181C and/or K103R resistant mutants.