Nonnucleoside human cytomegalovirus inhibitors: synthesis and antiviral evaluation of (chlorophenylmethyl)benzothiadiazine dioxide derivatives

A second generation of benzothiadiazine dioxide (BTD) derivatives was synthesized employing benzylation reactions mainly. The chlorophenylmethyl BTD derivatives showed activity against human cytomegalovirus (HCMV) with IC(50) values ranging from 3 to 10 microM. Their 50% cytotoxic concentrations were often >200 microM to lung fibroblast HEL cell proliferation and between 20 and 35 microM for lymphocyte CME cell growth. When cytotoxicity for cell morphology was considered, the minimum cytotoxic concentration for the different BTD derivatives varied between 5 and 200 microM. Some of the anti-HCMV compounds also showed activity against HIV-1 and HIV-2. The chlorophenylmethyl derivative 21 was active against a variety of HCMV clinical isolates from patients with different clinical manifestations and fully maintained its activity against a ganciclovir-resistant HCMV strain. The dibenzyl BTD derivatives did not inhibit HCMV protease, and preliminary pharmacological experiments revealed that their anti-HCMV action stems from interference with an early stage of the viral replicative cycle.     

Inhibitory activity and protein binding of L-lysine derivatives as angiotensin converting enzyme inhibitors

Four compounds 1a-4a containing one L-lysine residue in the molecule including a diastereomer mixture of lisinopril (N-(1-carboxy-3-phenylpropyl)-L-lysyl-L-proline) and N epsilon-carbobenzoxy-L-lysine derivatives 1b-4b of each of the four compounds were synthesized to compare the angiotensin converting enzyme (ACE) inhibitory activities in vitro and in vivo. They all showed high ACE inhibitory activity in vitro (IC50 = 0.14-42 nmol/l). A marked difference, however, was observed in inhibition of the pressor response to angiotensin I between 1a-4a (high activity) and 1b-4b (low activity). The binding of these compounds to human serum proteins in vitro was investigated by means of equilibrium dialysis and ultracentrifugation. Compounds 1b-4b showed higher levels of binding to serum albumin than that of the corresponding compounds 1a-4a, and the percentage of binding ranged from 20.1 to 89.1%. Furthermore, the inhibitory activity of compounds 1b-4b in vitro was decreased by the addition of albumin in a concentration-dependent manner. These results suggested that the difference in the protein binding rate of compounds is one of the important factors influencing the inhibitory activity in vivo.     

Insight into the structural requirements of benzothiadiazine scaffold-based derivatives as hepatitis C virus NS5B polymerase inhibitors using 3D-QSAR, molecular docking and molecular dynamics

Hepatitis C virus (HCV) infection is a significant world health threat with frequently ineffective problem existed in the present treatment, thus representing a major unmet medical need. The nonstructural viral protein 5B (NS5B), one of the best-studied polymerase, has emerged as an attractive target for the development of novel therapeutics against hepatitis C virus. In this work, both ligand- and receptor- based three-dimensional quantitative structure activity relationship (3D-QSAR) studies were carried out using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) techniques on 360 benzothiadiazine scaffold-based derivatives as HCV GT-1b NS5B polymerase allosteric inhibitors. The resultant optimum 3D-QSAR model exhibited R(2)(ev) of 0.54, R(2)(nev) of 0.72 and the predictive ability was validated by using an independent test set of 90 compounds which gave R(2)(pred) value of 0.64. In addition, docking analysis and molecular dynamics simulation (MD) were also applied to elucidate the probable binding modes of these inhibitors at the allosteric site of the enzyme. Interpretation of the 3D contour maps in context of the topology of the allosteric binding site of NS5B provided insight into NS5B-inhibitor interactions. The information obtained from this work can be utilized to accurately predict the binding affinity of related analogues and also facilitate the future rational design of novel inhibitors with improved activity.     

Pyrazolobenzotriazinone derivatives as COX inhibitors: synthesis, biological activity, and molecular-modeling studies

Pyrazolylbenzotriazinones are endowed with a structural analogy with the COX-2 selective inhibitor celecoxib. Considering that our research group has long been interested in the 3-pyrazolyl-substituted benzotriazinones as anti-inflammatory agents, six new pyrazolylbenzotriazinone derivatives 16a-c and 18a-c have been prepared by reacting the opportune ethyl 5-(2-aminobenzamido)-1-(pyridin-2-yl)-1H-pyrazole-4-carboxylate or 5-(2-aminobenzamido)-1-(pyridin-2-yl)-1H-pyrazole-4-carboxyic acid with sodium nitrite in glacial acetic acid. The biological studies revealed a good pharmacological profile for some pyrazolylbenzotriazinones and, in the case of the ethyl 5-(4-oxo-1,2,3-benzotriazin-3(4H)-yl)-1-pyridin-2-yl-1H-pyrazole-4-carboxylate, a good COX-1/COX-2 selectivity. Molecular modeling studies confirmed the obtained biological results.     

A novel class of geldanamycin derivatives as HCV replication inhibitors targeting on Hsp90: synthesis, structure-activity relationships and anti-HCV activity in GS4.3 replicon cells

A novel class of geldanamycin (GA) derivatives as hepatitis C virus (HCV) replication inhibitors has been synthesized and their anti-HCV activities were evaluated in GS4.3 HCV replicon cells. Most of the synthesized compounds demonstrated potential activities against HCV in vitro. Substitution with an aliphatic cyclic group (2b) and polar phosphate group (2f) at the 17 position of GA resulted in more potent inhibitory activity. The configurations of the tetrahydrofurfurylamino (THFM) substituents obviously affected their antiviral activities. The 2b with a 2'-(R)-THFM group at the 17 position showed much potent activity and higher selectivity than its 2'-(S) and 2'-(R, S) epimers. In the tested GA derivatives, 2b and 2f show the most potential leading compounds for development of novel anti-HCV agents.     

Synthesis and antitumor activity of novel diaryl ether hydroxamic acids derivatives as potential HDAC inhibitors

A series of diaryl ether hydroxamic acids were synthesized for the first time and evaluated for the HDAC biology and antiproliferative activity. The structures of these new hydroxamic acids derivatives were confirmed by IR, ¹H-NMR and mass spectrum. Some of these compounds showed micro molar activity in the HDAC inhibitory assay and against four cancer cell lines.     

Identification and structure–activity relationship of purine derivatives as novel MTH1 inhibitors

The human mutT homolog‐1 (MTH1) protein prevents the incorporation of oxidized nucleotides such as 2‐OH‐dATP and 8‐oxo‐dGTP during DNA replication by hydrolyzing them into their corresponding monophosphates. It was found previously that cancer cells could tolerate oxidative stress due to this enzymatic activity of MTH1 and its inhibition could be a promising approach to treat several types of cancer. This finding has been challenged recently with increasing line of evidence suggesting that the cancer cell‐killing effects of MTH1 inhibitors may be related to their engagement of off‐targets. We have previously reported a few purine‐based MTH1 inhibitors that enabled us to elucidate the dispensability of MTH1 in cancer cell survival. Here, we provide a detailed process of the identification of purine‐based MTH1 inhibitors. Several new compounds with potency in the submicromolar range are disclosed. Furthermore, the structure–activity relationship and associated binding mode prediction using molecular docking have provided insights for the development of highly potent MTH1 inhibitors.     

beta-Lactam derivatives as enzyme inhibitors: 1-peptidyl derivatives of 4-phenylazetidin-2-one as inhibitors of elastase and papain

N-Peptidyl substituted azetidin-2-ones were synthesized and evaluated as inhibitors of the serine protease elastase, and the cysteine protease papain. All compounds were synthesized from 4-phenylazetidin-2-one, either from the racemate or from the pure enantiomers. The (S)-enantiomer was prepared by enantioselective synthesis from (S)-beta-phenyl-beta-alanine, while the (R)-enantiomer was obtained by enzymatic resolution with alpha-chymotrypsin. N-Alkylation with bromoacetates introduced a spacer group which, after hydrolysis to the free acid, was acylated with amino acid esters or di- or tripeptide esters. The enzymatic assays proved some derivatives to be effective inhibitors of PPE and/or papain. N-BOC protected amino acid derivatives without a spacer group inhibited PPE reversibly, while derivatives with spacer group showed either weak or no inhibitory properties. On the other hand, papain was inactivated irreversibly by ethyl (RS)-2-oxo-4-phenylazetidin-1-acetate. The highest inhibitory activity against papain was found for the diastereomers of N-(2-oxo-4-phenylazetidin-1-acetyl)-L-alanyl-L-valine benzyl ester, a compound with a spacer group.     

Synthesis of glabridin derivatives as tyrosinase inhibitors

A novel 3″,4″-dihydroglabridin was successfully prepared for studying on tyrosinase inhibitory activity. The result demonstrated that 3″,4″-dihydroglabridin exhibited higher activity than glabridin (IC₅₀ value = 11.40 μM), which is probably due to the 4-substituted resorcinol skeleton and the lacking of double bond between carbon atom 3″ and 4″ on its structure giving more conformational flexibily to interact with the enzyme more effectively. In addition, various acylated derivatives were synthesized as glabridin prodrugs. The chemical and enzymatic hydrolysis of prodrugs revealed that the diacetate ester was rapidly hydrolyzed by porcine liver esterase with the half-life of 2.36 minute, while those of the dihexanoate was 14.8 hour. Both of them were sufficiently stable in phosphate buffer, both pH 5.5 and 7.4, at 37°C with more than 15 days half-life.     

Dimeric cinnamoylamide derivatives as inhibitors of melanogenesis

Dimeric cinnamoylamide derivatives were synthetized and tested as inhibitors of tyrosinase activity and melanin formation. The most active dimeric cinnamoylamide derivatives was dimeric compound of p-coumaric acid (compound 1) that inhibited tyrosinase activity more efficiently than p-coumaric acid. It also inhibited melanin production by B16 melanoma cell line and normal human melanocytes more efficiently than kojic acid. We next investigated the potential mutagenic and skin sensitization effect of compound 1. Compound 1 was found to induce no mutagenic activity, no irritation and no delayed contact hypersensitivity at the maximum concentration of 10%. In vitro percutaneous absorption studies exhibited that compound 1 could diffuse across the skin till its site of action. All these results lead us to propose that compound 1 may be a safe and effective candidate for treating skin hyperpigmentation related disorders.