Structure–activity relationship of antileishmanials neolignan analogues

Synthesis and evaluation of hybrid sulfonamide-chalcones with potential antileishmanial activity

Leishmaniasis is an emerging tropical infectious disease caused by a protozoan parasite of the genus Leishmania. In this work, the molecular hybridization between a trimethoxy chalcone and a sulfonamide group was used to generate a series of sulfonamide-chalcones. A series of eight sulfonamide-chalcone hybrids were made with good yields (up to 95%). These sulfonamide-chalcones were tested against promastigotes of Leishmania amazonensis and cytotoxicity against mouse macrophages, which showed good antileishmanial activity with IC50  = 1.72-3.19 µM. Three of them (10c, 10g, and 10h) were also highly active against intracellular amastigotes and had a good selectivity index (SI > 9). Thus, those three compounds were docked in the cytosolic tryparedoxin peroxidase (cTXNPx) enzyme of the parasite, and molecular dynamics simulations were carried out. This enzyme was selected as a target protein for the sulfonamide-chalcones due to the fact of the anterior report, which identified a strong and stable interaction between the chalcone NAT22 (6) and the cTXNPx. In addition, a prediction of the drug-likeness, and the pharmacokinetic profile of all compounds were made, demonstrating a good profile of those chalcones.

Straightforward access to α-carbonyloxy esters and β-keto thioethers from aryldiazoacetates

A metal- and additive-free approach has been described for synthesizing α-carbonyloxy esters and β-keto thioethers from readily available aryldiazoacetates with carboxylic acids and thiol derivatives, respectively. α-Carbonyloxy esters and β-keto thioether derivatives were synthesized in good to high yields from aryldiazoacetates, carboxylic acids, and thiol derivatives decorated with various functional groups. Finally, the potential of the new approach is demonstrated through its application in gram-scale reactions and the synthesis of a few bioactive molecules.

Synthesis of α-sulfenylated carbonyl compounds under metal-free conditions

An efficient synthesis of α-sulfenylated carbonyl compounds from propargylic alcohols and aryl thiols under heating conditions is described. The method is characterized by mild conditions, simple operation, metal-free catalysis and good functional group tolerance. Mechanistic studies suggest that the reaction involves a radical pathway and an isomerization process.

DBU-Catalyzed Aerobic CDC Reaction of Thiophenols

A convenient method was developed for the preparation of thiolated compounds via a DBU-catalyzed aerobic cross-dehydrogenative coupling (CDC) reaction. The established protocol is environmentally friendly and operationally simple. Substrates like (hetero)aryl acetates, (hetero)aryl ketones, and indoles could be transformed into the corresponding thiolated products in moderate to high yields and further applied in the preparation of bioactive compounds in a prefunctionalization-free manner.

Identification of potential inhibitors of Schistosoma mansoni purine nucleoside phosphorylase from neolignan compounds using molecular modelling approaches

Schistosomiasis is a parasitic disease that is part of the neglected tropical diseases (NTDs), which cause significant levels of morbidity and mortality in millions of people throughout the world. The enzyme purine nucleoside phosphorylase from Schistosoma mansoni (SmPNP) represents a potential target for discovering new agents, and neolignans stand out as an important class of compounds. In this work, molecular modeling studies and biological assays of a set of neolignans were conducted against the PNP enzymes of the parasite and the human homologue (HssPNP). The results of the molecular docking described that the neolignans showed good complementarity by the active site of SmPNP. Molecular dynamics (MD) studies revealed that both complexes (Sm/HssPNP - neolignan compounds) were stable by analyzing the root mean square deviation (RMSD) values, and the binding free energy values suggest that the selected structures can interact and inhibit the catalytic activity of the SmPNP. Finally, the biological assay indicated that the selected neolignans presented a better molecular profile of inhibition compared to the human enzyme, as these ligands did not have the capacity to inhibit enzymatic activity, indicating that these compounds are promising candidates and that they can be used in future research in chemotherapy for schistosomiasis.Communicated by Ramaswamy H. Sarma.

Assessing Methodologies to Synthesize α-Sulfenylated Carbonyl Compounds by Green Chemistry Metrics

α-Sulfenylated carbonyl compounds are important both as active pharmaceutical ingredients and as intermediates in organic synthesis. Owing to their relevance in synthetic organic chemistry, this Minireview focuses on assessing the most relevant synthetic procedures based on green chemistry metrics. The Minireview starts with the traditional routes and then focuses on more recently developed methodologies. These routes include sulfenylating reagents using organocatalysis, cross-dehydrogenative couplings using in situ halogenations to prevent reactive intermediates in high concentrations, oxidative couplings using terminal oxidants such as DDQ or TEMPO, and redox-neutral couplings using transition metal catalysis. These methodologies have been evaluated on the basis of atom economy, E factor, and the safety and toxicity of the transformations and the solvents used. Besides using green metrics to evaluate these novel methodologies, the synthetic utility is also assessed with regard to the availability of starting materials and the generality of the reactions. This Minireview aims to inspire researchers to apply green assessments to other methodologies and also for them to take measures to increase the greenness of their developed transformations.

Total Synthesis of Surinamensinols A and B

An efficient total synthesis of the naturally occurring anti-inflammatory and antitumour 8-O-4′-neolignans, surinamensinols A and B, has been accomplished from commercially available allyl alcohol and (S)-ethyl lactate. The synthetic sequence involves a palladium-catalysed Suzuki–Miyaura cross-coupling reaction followed by a chiral Mitsunobu­ reaction as the key steps. This is the first report of the simultaneous stereoselective total synthesis of surinamensinols A and B through a single approach involving only six steps.

High-Atom Economic Approach To Prepare Chiral α-Sulfenylated Ketones

Chiral α-sulfenylated ketones are versatile building blocks, although there are still several limitations with their preparation. Here we report a new two-step procedure, consisting of Pd-catalyzed hydrothiolation of propargylic alcohols followed by an enantioselective Rh isomerization of allylic alcohols. The isomerization reaction is the key step for obtaining the ketones in their enantioenriched form. The new methodology has a high atom economy and induces good to high levels of enantioselectivity; no waste is produced. A mechanism involving a Rh-hydride-enone intermediate is proposed for the isomerization reaction.

A one-pot protocol for the synthesis of β-ketosulfones from α,α-dibromoketones

A one-pot debromination/sulfonylation strategy was developed for the direct transformation of α,α-dibromoketones into β-ketosulfones in the presence of sulfinate salts in a methanol solution.

Electrochemical oxidative oxysulfenylation and aminosulfenylation of alkenes with hydrogen evolution

Difunctionalization of alkenes is a valuable and versatile chemical transformation that could quickly build complex molecules. Extensive efforts have been made, and great achievement, such as Sharpless aminohydroxylation and dihydroxylation, has been reached. However, in marked contrast to the extensive research of aminohydroxylation and dihydroxylation, directly using thiophenols/thiols and O/N-nucleophiles to perform the difunctionalization of alkenes that form the C-S and C-O/N bonds together is still underexplored. The main issue is that thiophenols/thiols are often easily overoxidized to sulfoxides or sulphones under such essential oxidation conditions. We demonstrate an electrochemical oxidative oxysulfenylation and aminosulfenylation of alkenes. A critical feature of this transformation is that neither external chemical oxidants nor metal catalysts are required. This electrochemical oxidative synthetic strategy could also be applied for the hydroxysulfenylation and acyloxysulfenylation of alkenes.

Synthesis, characterization, and third-order nonlinear optical properties of a new neolignane analogue

This paper presents an extensive study of a new neolignane analogue using experimental and theoretical approach and brings highlights in solid state characterization and electronic properties.

Genotoxicity and Cytotoxicity Evaluation of the Neolignan Analogue 2-(4-Nitrophenoxy)-1Phenylethanone and its Protective Effect Against DNA Damage

Neolignans are secondary metabolites found in various groups of Angiosperms. They belong to a class of natural compounds with great diversity of chemical structures and pharmacological activities. These compounds are formed by linking two phenylpropanoid units. Several compounds that have ability to prevent genetic damage have been isolated from plants, and can be used to prevent or delay the development of tumor cells. Genetic toxicology evaluation is widely used in risk assessment of new drugs in preclinical screening tests. In this study, we evaluated the genotoxicity and cytotoxicity of the neolignan analogue 2-(4-nitrophenoxy)-1-phenylethanone (4NF) and its protective effect against DNA damage using the mouse bone marrow micronucleus test and the comet assay in mouse peripheral blood. Our results showed that this neolignan analogue had no genotoxic activity and was able to reduce induced damage both in mouse bone marrow and peripheral blood. Although the neolignan analogue 4NF was cytotoxic, it reduced cyclophosphamide-induced cytotoxicity. In conclusion, it showed no genotoxic action, but exhibited cytotoxic, antigenotoxic, and anticytotoxic activities.

Computational modelling of the antischistosomal activity for neolignan derivatives based on the MIA-SAR approach

Theoretical models for exploring the antischistosomal activity of a dataset of 18 synthetic neolignans are built using the multivariate image analysis applied to structure-activity relationships (MIA-SAR) approach. The obtained models were validated using the accuracy (Acc) in leave-one-out cross-validation, external validation and Y-randomization procedures, yielding correct classification superior to 80%, 70% and 60%, respectively. Additionally, a comparison was made of the models obtained from binary (black and white) and coloured images; the colours (pixel values) were selected to correspond to chemical properties. It was observed that the models obtained from coloured images with pixel values corresponding to electronegativity (known as the aug-MIA-SAR(colour) approach) generally yielded superior statistical parameters compared with those obtained from binary images (MIA-SAR) and randomly coloured images (atoms are coloured according to their type) with atomic sizes corresponding to Van der Waals radius (aug-MIA-SAR), respectively. Mechanistic interpretation of the influence of different substituents on the antischistosomal activity revealed that methoxy substituents in the R1 (or R2) and R5 positions of the neolignan scaffold are indispensable for the antischistosomal activity. The obtained results provide knowledge of the possible structural modifications to yield novel neolignan compounds with antischistosomal activity.

Asymmetric synthesis and anti-protozoal activity of the 8,4'-oxyneolignans virolin, surinamensin and analogues

The asymmetric synthesis of 8,4'-oxyneolignans (-)-virolin, (-)-surinamensin and a number of analogues has been achieved. A divergent synthesis was used, with all compounds being elaborated from a single chiral aldehyde derived from ethyl lactate. In the 15 compounds that were tested, the level of substitution on the A-ring was found to directly influence the activity against Leishmania donovani whilst the activity against Plasmodium falciparum was influenced by numerous substitution and stereochemical factors.

Effects of the antimycobacterial compound 2-phenoxy-1-phenylethanone on rat hepatocytes and formation of metabolites

CONTEXT

Neolignans are usually dimers formed by oxidative coupling of allyl and propenyl phenols, and the neolignan analogue, 2-phenoxy-1-phenylethanone (LS-2) is a promising antimycobacterial compound showing very weak cytotoxicity in mammalian cells and lack of acute toxicity in murine models.

OBJECTIVES

To investigate the mechanism of action of LS-2 in rat hepatocytes by evaluating the activity levels of enzymes related to oxidation status and drug-metabolizing activity.

MATERIALS AND METHODS

Hepatocytes were treated with LS-2 from 0.05 up to 1 mM, for 24 and 48 h, and reduced glutathione (GSH), lipid peroxidation and cytochrome P450 enzyme (CYP450) activity were assayed. A homologous series of phenoxazone ethers were used as substrates to measure the enzymatic profile. The biotransformation of LS-2 was studied in hepatocytes by gas chromatography-mass spectrometry (GC-MS) for detection and analysis of possible metabolites.

RESULTS

Hepatocytes treated with LS-2 up to 1 mM for 24 or 48 h did not induce the formation of GSH and lipid peroxidation. O-Dealkylation activities of the isoenzymes CYP4501A1, CYP4501A2, CYP4502B1 and CYP4502B2 were also not detected in the hepatocytes treated with LS-2 for 24 or 48 h.

DISCUSSION AND CONCLUSION

The results indicate that LS-2 or its two detected metabolites, 2-phenoxy-1-phenylethanol and 2,4-(2-hydroxy-2-phenylethoxy)phenol, are not cytotoxic to rat hepatocytes. These compounds maintain a balance between the production of pro-oxidant agents and their respective antioxidant systems. The data show that enzymes related to oxidation status and drug-metabolizing activities are not involved in the mechanism of action of LS-2.

Synthesis of (1R,2S)-2-(4′-Allyl-2′,6′-Dimethoxyphenoxyl)-1-(4″-Hydroxy-3″, 5″-Dimethoxyphenyl)Propan-1-ol

The asymmetric synthesis of the natural neolignan (1R,2S)-2-(4′-allyl-2′,6′-dimethoxyphenoxyl)-1-(4″-hydroxy-3″,5″-dimethoxyphenyl)propan-1-ol based on an asymmetric dihydroxylation as a key reaction using AD-mix-β to preparing the chiral threo-(1R,2R)-glycerol. The reaction, threo-alcohols were inverted by an SN2 reaction into erythro-(1R,2S)-isomers.

Structure activity relationship, acute toxicity and cytotoxicity of antimycobacterial neolignan analogues

OBJECTIVES

The study's aims were to evaluate the antimycobacterial activity of 13 synthetic neolignan analogues and to perform structure activity relationship analysis (SAR). The cytotoxicity of the compound 2-phenoxy-1-phenylethanone (LS-2, 1) in mammalian cells, such as the acute toxicity in mice, was also evaluated.

METHODS

The extra and intracellular antimycobacterial activity was evaluated on Mycobacterium tuberculosis H37Rv. Cytotoxicity studies were performed using V79 cells, J774 macrophages and rat hepatocytes. Additionally, the in-vivo acute toxicity was tested in mice. The SAR analysis was performed by Principal Component Analysis (PCA).

KEY FINDINGS

Among the 13 analogues tested, LS-2 (1) was the most effective, showing promising antimycobacterial activity and very low cytotoxicity in V79 cells and in J774 macrophages, while no toxicity was observed in rat hepatocytes. The selectivity index (SI) of LS-2 (1) was 91 and the calculated LD50 was 1870 mg/kg, highlighting the very low toxicity in mice. SAR analysis showed that the highest electrophilicity and the lowest molar volume are physical-chemical characteristics important for the antimycobacterial activity of the LS-2 (1).

CONCLUSIONS

LS-2 (1) showed promising antimycobacterial activity and very weak cytotoxicity in cell culture, as well as an absence of toxicity in primary culture of hepatocytes. In the acute toxicity study there was an indication of absence of toxicity on murine models, in vivo.

Selective one-pot multicomponent synthesis and anti-tubercular evaluation of 5-(aryl/cyclohexylsulfanyl)-2-alkoxy-4,6-diarylnicotinonitriles

A new set of highly substituted pyridine derivatives has been synthesized by a product selective four component reaction of aryl aldehyde, malononitrile and 2-aryl/cyclohexylsulfanyl-1-aryl-1-ethanones in presence of sodium hydroxide in methyl/ethyl alcohol. Among the compounds, 4,6-bis(4-chlorophenyl)-5-[(4-chlorophenyl)sulfanyl]-2-methoxynicotinonitrile (4n) inhibited Mycobacterium tuberculosis (MTB) with minimum inhibitory concentration (MIC) of 3.1 microM and was more potent than ethambutol and pyrazinamide.