Synthesis and biological evaluation of new symmetrical derivatives as cytotoxic agents and apoptosis inducers

Design and Synthesis of Polyheterocyclic Compounds Containing Pyrazolopyridopyrimidine Nucleus with Antimicrobial Activities

This study reports the design, synthesis, and antibacterial evaluation of a library of novel polyheterocyclic derivatives featuring a unique fused pyrimidopyridopyrazole moiety. A cyclocondensation reaction between an amino-pyrazolopyridopyrimidine precursor and malonates afforded a series of pyrimidopyridopyrazolopyrimidine derivatives. Further diversification was achieved through nucleophilic cyclocondensation, yielding a collection of complex polyheterocyclic systems encompassing various ring structures. All synthesized compounds were rigorously characterized using spectroscopic techniques and elemental analysis. The antibacterial activity of the newly synthesized compounds was assessed against a panel of Gram-positive and Gram-negative bacteria. Notably, several compounds exhibited promising antibacterial activity, highlighting their potential as leads for the development of novel antibiotics.

Catalysis-free synthesis of thiazolidine-thiourea ligands for metal coordination (Au and Ag) and preliminary cytotoxic studies

The reaction of propargylamines with isothiocyanates results in the selective formation of iminothiazolidines, aminothiazolines or mixed thiazolidine-thiourea compounds under mild conditions. It has been observed that secondary propargylamines lead to the selective formation of cyclic 2-amino-2-thiazoline derivatives, while primary propargylamines form iminothiazoline species. In addition, these cyclic thiazoline derivatives can further react with an excess of isothiocyanate to give rise to thiazolidine-thiourea compounds. These species can also be achieved by reaction of propargylamines with isothiocynates in a molar ratio of 1 : 2. Coordination studies of these heterocyclic species towards silver and gold with different stoichiometries have been carried out and complexes of the type [ML(PPh₃)]OTf, [ML₂]OTf (M = Ag, Au) or [Au(C₆F₅)L] have been synthesised. Preliminary studies of the cytotoxic activity in lung cancer cells have also been performed in both ligands and complexes, showing that although the ligands do not exhibit anticancer activity, their coordination to metals, especially silver, greatly enhances the cytotoxic activity.

Medicinal chemistry perspective of pyrido[2,3-d]pyrimidines as anticancer agents

Cancer is a major cause of deaths across the globe due to chemoresistance and lack of selective chemotherapy. Pyrido[2,3-d]pyrimidine is an emerging scaffold in medicinal chemistry having a broad spectrum of activities, including antitumor, antibacterial, CNS depressive, anticonvulsant, and antipyretic activities. In this study, we have covered different cancer targets, including tyrosine kinase, extracellular regulated protein kinases - ABL kinase, phosphatidylinositol-3 kinase, mammalian target of rapamycin, p38 mitogen-activated protein kinases, BCR-ABL, dihydrofolate reductase, cyclin-dependent kinase, phosphodiesterase, KRAS and fibroblast growth factor receptors, their signaling pathways, mechanism of action and structure-activity relationship of pyrido[2,3-d]pyrimidine derivatives as inhibitors of the above-mentioned targets. This review will represent the complete medicinal and pharmacological profile of pyrido[2,3-d]pyrimidines as anticancer agents, and will help scientists to design new selective, effective and safe anticancer agents.

Design, synthesis, in vitro and in silico bioactivity profiles of new urea/thiourea derivatives of 2-pyridyl piperazine as potent antioxidant and antimicrobial agents: chemo-bio-computational approach

Synthesis of a series of new urea and thiourea derivatives of 2-pyridyl piperazine was accomplished by reacting various isocyanates and isothiocyanates in the presence of triethylamine (TEA) at 50 °C. All the title compounds were obtained in high yields and their structures were characterized by IR, ¹H, ¹³C NMR, Mass spectral, and Elemental analysis. The synthesized compounds were screened for in vitro and in silico antioxidant and antimicrobial activities. All the title compounds exhibited potent antioxidant and antimicrobial activities. Out of all, 2c and 2f against DPPH, H₂O₂ and Nitro oxide have exhibited significant activity and the levels of activity were higher than the reference compounds, ascorbic acid and BHT. Whereas 2a, 2c, 2f and 2j have shown prominent activity in terms of zone of inhibition against all the microbial strains tested than the standards such as levofloxacin and nystatin. In addition in silico studies also conveyed the same that is 2a, 2c, 2f and 2j have displayed the highest binding energies against peroxiredoxins and DNA gyrase protein than the standards akin to the rest of the compounds. In overall, 2c and 2f have exhibited most promising antioxidant and antimicrobial activity than the rest of the title compounds in vitro and in silico. Hence, 2c and 2f will stand as a lead and promising antioxidant and antimicrobial drug candidates in future.

Synthesis of New Thiourea-Metal Complexes with Promising Anticancer Properties

In this work, two thiourea ligands bearing a phosphine group in one arm and in the other a phenyl group (T2) or 3,5-di-CF₃ substituted phenyl ring (T1) have been prepared and their coordination to Au and Ag has been studied. A different behavior is observed for gold complexes, a linear geometry with coordination only to the phosphorus atom or an equilibrium between the linear and three-coordinated species is present, whereas for silver complexes the coordination of the ligand as P^S chelate is found. The thiourea ligands and their complexes were explored against different cancer cell lines (HeLa, A549, and Jurkat). The thiourea ligands do not exhibit relevant cytotoxicity in the tested cell lines and the coordination of a metal triggers excellent cytotoxic values in all cases. In general, data showed that gold complexes are more cytotoxic than the silver compounds with T1, in particular the complexes [AuT1(PPh₃)]OTf, the bis(thiourea) [Au(T1)₂]OTf and the gold-thiolate species [Au(SR)T1]. In contrast, with T2 better results are obtained with silver species [AgT1(PPh₃)]OTf and the [Ag(T1)₂]OTf. The role played by the ancillary ligand bound to the metal is important since it strongly affects the cytotoxic activity, being the bis(thiourea) complex the most active species. This study demonstrates that metal complexes derived from thiourea can be biologically active and these compounds are promising leads for further development as potential anticancer agents.

Synthesis and In Silico Docking of New Pyrazolo[4,3-e]pyrido[1,2-a]pyrimidine-based Cytotoxic Agents

To explore a new set of anticancer agents, a novel series of pyrazolo[4,3-e]pyrido[1,2-a]pyrimidine derivativeshave been designed and synthesized viacyclocondensation reactions of pyrazolo-enaminone with a series of arylidenemalononitriles; compound 5 was obtained from 5-amino-4-cyanopyrazole. The structures of the target compounds were investigated by spectral techniques and elemental analysis (IR, UV-Vis, ¹H NMR, ¹³C NMR and ESI-MS). All compounds were evaluated for their in vitro cytotoxicity employing a panel of different human tumor cell lines, A375, HT29, MCF7, A2780, FaDu as well as non-malignant NIH 3T3 and HEK293 cells. It has been found that the pyrazolo-pyrido-pyrimidine analog bearing a 4-Br-phenyl moiety was the most active toward many cell lines with EC₅₀ values ranging between 9.1 and 13.5 µM. Moreover, in silico docking studies of the latter with six anticancer drug targets, i.e., DHFR, VEGFR2, HER-2/neu, hCA-IX, CDK6 and LOX5, were also performed, in order to gain some insights into their putative mode of binding interaction and to estimate the free binding energy of this bioactive molecule.

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

Design and synthesis of a series of pyrido[2,3-d]pyrimidine derivatives as CCR4 antagonists

A series of pyrido[2,3-d]pyrimidine derivatives were designed and synthesized based on known CC chemokine receptor 4 (CCR4) antagonists. The activities of all the newly synthesized compounds were evaluated using a chemotaxis inhibition assay. Compound 6b was proven to be a potent CCR4 antagonist that can block cell chemotaxis induced by macrophage-derived chemokine (MDC), thymus and activation regulated chemokine (TARC), and CKLF1, the natural ligands of CCR4. In addition, compound 6b is more effective than budesonide in the murine rhinitis model. The intravenous injection LD₅₀ of compound 6b is 175 mg/kg and the oral LD₅₀ is greater than 2,000 mg/kg.

Sulfur and selenium derivatives of quinazoline and pyrido[2,3-d]pyrimidine: synthesis and study of their potential cytotoxic activity in vitro

The synthesis, cytotoxic activities and selectivities of 35 derivatives related to quinazoline and pyrido[2,3-d]pyrimidine are described. The synthesized compounds were screened in vitro against four tumoral cell lines - leukemia (CCRF-CEM), colon (HT-29), lung (HTB-54) and breast (MCF-7) - and two cell lines derived from non-malignant cell lines, one mammary (184B5) and one from bronchial epithelium (BEAS-2B). MCF-7 and HTB-54 were the most sensitive cell lines with GI(50) values below 10μM for eleven and ten compounds, respectively. Two compounds (2o and 3a) were identified that evoked a marked cytotoxic effect in all cell lines tested and one compound, 7h, was potent and selective against MCF-7. A preliminary study into the mechanism of the potent derivatives 2o, 3a and 7h indicated that the cytotoxic activities of these compounds might be mediated by inducing cell death without affecting cell cycle phases.

New insights into the structural requirements for pro-apoptotic agents based on 2,4-diaminoquinazoline, 2,4-diaminopyrido[2,3-d]pyrimidine and 2,4-diaminopyrimidine derivatives

As a continuation of our work on new anti-tumoral derivatives with selective pro-apoptotic activity in cancer cells, we describe the synthesis and the preliminary evaluation of the cytotoxic and pro-apoptotic activities of a series of pyrimidin-2,4-diamine derivatives that are structurally related to quinazolin-2,4-diamine and pyrido[2,3-d]pyrimidin-2,4-diamine derivatives. We also describe the structure-activity relationship studies carried out on four series' of quinazolin-2,4-diamine, 2-(alkylsulfanyl)-N-alkyl- and 2-(alkylsulfanyl)-N-alkylarylpyrido[2,3-d]pyrimidine and pyrimidin-2,4-diamine derivatives. The proposed preliminary pharmacophore consists of a flat heterocyclic ring, preferably a pyrido[2,3-d]pyrimidine, with two equivalent alkylarylamine chains, preferably N-benzyl- or N-ethylphenylamine, located in positions 2 and 4 of the ring, and with a preferred ALogP in the range 4.5-5.5. The nitrogen present in the central ring can act as hydrogen bond acceptors (HBA) whereas the amino group in the 4-position can act as a donor (HBD) or an HBA and the amino group in the 2-position can act as an HBD. On the basis of the analyzed structural profiles, different mechanisms of action can be suggested for the quinazolin-2,4-diamine, the 2-(alkylsulfanyl)-N-alkylpyrido[2,3-d]pyrimidin-4-amine and the pyrido[2,3-d]pyrimidin-2,4-diamine derivatives.

Synthesis and in vitro cytotoxic activity of compounds with pro-apoptotic potential

In our search for new anticancer therapies, some compounds synthesized in our lab were selected and their potential cytotoxic activity was evaluated in vitro against two cancer cells lines including a solid tumor (UACC-62, melanoma) and a human lymphoma (JURKAT). Compounds showing cytotoxic activity were subjected to an apoptosis assay. Two compounds showed promising results.

Novel benzothiazolyl urea and thiourea derivatives with potential cytotoxic and antimicrobial activities

A novel series of benzothiazole urea and thiourea derivatives was synthesized and evaluated for its in vitro cytotoxicity against MCF-7 breast cancer cells. The N1-(benzothiazol-2-yl)-N3-morpholinourea 3 displayed the highest cytotoxic activity in this series. A docked pose of 3 was obtained bound to G-quadruplex of human telomere DNA active site using the Molecular Operating Environment (MOE) module. Moreover, the synthesized compounds were screened for their antimicrobial activity against Mycobacterium tuberculosis H37Rv, E. coli, S. aureus and C. albicans. Again, 3 showed the best activity against M. tuberculosis H37Rv while other compounds were equipotent with ampicillin against S. aureus and E. coli.

Novel potent organoselenium compounds as cytotoxic agents in prostate cancer cells

A series of 17 symmetrical substituted imidothiocarbamate and imidoselenocarbamate derivatives has been synthesized by reacting appropriately substituted acyl chlorides with alkyl imidothiocarbamates and alkyl imidoselenocarbamates. The antitumoral activities of the compounds were evaluated in vitro by examining their cytotoxic effects against human prostate cancer cells (PC-3). Five compounds showed interesting activity levels and 3p (IC(50)=1.85 microM) was 7.3 times more active than the standard etoposide used in the treatment of prostate cancer and emerges as the most interesting compound.

In vitro apoptotic activity of 2,2-diphenyl-1,3,2-oxazaborolidin-5-ones in L5178Y cells

Compounds containing B-N bonds have shown interesting biological activity. One class of such molecules is the 2,2-diphenyl-1,3,2-oxazaborolidin-5-ones (3a-j), which contain a B-N bond, have an alpha-amino acid moiety in the heterocycle, and have an exocyclic moiety related to an amino acid. The purpose of this work was to determine the inhibitory effects of 3a-j on the proliferation of murine L5178Y lymphoma cells. A new five-membered heterocyclic nucleus with apoptotic activity was found. The target products showed potent cytotoxicity in the L5178Y cell line. Among them, 3a exhibited the highest antineoplastic activity in L5178Y cells with an IC(50) value of 22.5+/-0.2 microM.

Biological profile of new apoptotic agents based on 2,4-pyrido[2,3-d]pyrimidine derivatives

In order to obtain less toxic antitumoral compounds we have looked for novel compounds with anticancer activity based on proapoptotic mechanisms. The compounds studied in this work are derivatives of bicyclic aromatic systems like pyrido[2,3-d]pyrimidines. The potential antitumoral activity of the compounds was evaluated in vitro by examining their cytotoxic effects against human breast, colon, and bladder cancer lines (MD-MBA-231, HT-29, and T-24). The data indicate that HC-6 is a potent anticancer drug showing dose-dependent cytostatic and proapoptotic effects through activation of two different signaling pathways namely a pathway leading to cell cycle arrest and a transcription-independent route leading to rapid apoptosis.

Core exploration in optimization of chemokine receptor CCR4 antagonists

The design, synthesis, and SAR studies of 'core' variations led to identification of novel, selective, and potent small molecule antagonist (22) of the CC chemokine receptor-4 (CCR4) with improved in vitro activity and liability profile. Compound 22 was efficacious in a murine allergic inflammation model (ED50 approximately 10 mg/kg).

Acid-Catalyzed Synthesis of Methylene-Bridged (S)-Tyrosine−Phenol Dimers

The efficient synthesis of 2,2'-arylmethylene dimers from 3-hydroxymethyl or 3-methoxymethyl-5-halo-(S)-tyrosines and para-substituted phenols under acid-catalyzed reaction conditions using either conventional or microwave-assisted protocols is described.

Cytotoxic effects and apoptotic signalling mechanisms of the sesquiterpenoid euplotin C, a secondary metabolite of the marine ciliate Euplotes crassus, in tumour cells

Most antitumour agents with cytotoxic properties induce apoptosis. The lipophilic compound euplotin C, isolated from the ciliate Euplotes crassus, is toxic to a number of different opportunistic or pathogenic microorganisms, although its mechanism of action is currently unknown. We report here that euplotin C is a powerful cytotoxic and pro-apoptotic agent in mouse AtT-20 and rat PC12 tumour-derived cell lines. In addition, we provide evidence that euplotin C treatment results in rapid activation of ryanodine receptors, depletion of Ca2+ stores in the endoplasmic reticulum (ER), the release of cytochrome c from the mitochondria, activation of caspase-12, and activation of caspase-3, leading to apoptosis. Intracellular Ca2+ overload is an early event which induces apoptosis and is parallelled by ER stress and the release of cytochrome c, whereas caspase-12 may be activated by euplotin C at a later stage in the apoptosis pathway. These events, either independently or concomitantly, lead to the activation of the caspase-3 and its downstream effectors, triggering the cell to undergo apoptosis. These results demonstrate that euplotin C may be considered for the design of cytotoxic and pro-apoptotic new drugs.

Synthesis and Biological Evaluation of Heteroaryldiamides and Heteroaryldiamines as Cytotoxic Agents, Apoptosis Inducers and Caspase-3 Activators

The work described here involved the synthesis and biological evaluation of new heteroaryldiamides and heteroaryldiamines. A new general model in which the structures can be adjusted has been applied in this study. Three different structural units can be distinguished: a central nucleus and two symmetric terminal units. The central element is either an aliphatic chain of varying length and flexibility, piperazine, or a polyamine nucleus. However, the terminal units are pyridine, quinoline, indole, benzene or pyrido[2,3-d]pyrimidine with different substituents. The antitumoural activities of the compounds were evaluated in vitro by examining their cytotoxic effects against human breast, colon, and bladder cancer cell lines. Compounds that showed cytotoxic activity were subjected to both apoptosis and caspase-3 assays. With regard to selectivity, the cytotoxicity was also determined in cell cultures of two nontumoural lines. The most promising compounds are 4c, 5c and 7, which are amino-pyridinium, quinolyl-N-oxide, and pyridyl derivatives, respectively, and these reveal a significant in vitro cytotoxicity in at least two of the three cell lines tested. These compounds induced apoptosis and also produced a rapid dose-dependent increase in the caspase-3 level in HT-29 cells. Other encouraging profiles were found, such as those presented by 1k and 8d, which are cytotoxic and apoptotic but do not provoke an increase in the level of caspase-3, or those presented by 2f, 3c and 4a, which are slightly cytotoxic but do not show any other significant activity. The different types of behaviour of each compound are not necessarily parallel in the three cell lines tested.

Structural characteristics of novel symmetrical diaryl derivatives with nitrogenated functions. Requirements for cytotoxic activity

In an attempt to discover the essential features that would allow us to explain the differences in cytotoxic activity shown by a series of symmetrical diaryl derivatives with nitrogenated functions, we have studied by molecular modelling techniques the variation in Log P and conformational behaviour, in terms of structural modifications. The Log P data--although they provide few clues concerning the observed variability in activity--suggest that an initial separation of active and inactive compounds is possible based on this parameter. The subsequent study of the conformational behaviour of the compounds, selected according to their Log P values, showed that the active compounds preferentially display an extended conformation and inactive ones are associated with a certain type of folding, with a triangular-type conformation adopted in these cases.

New Approach to the Practical Synthesis of Tri- or Tetrasubstituted Pyrimidine Derivatives: A Four-Component Coupling Reaction from a Functionalized Silane, Two Types of Aromatic Nitriles, and Acetals

[reaction: see text] A new approach to the synthesis of tri- or tetrasubstituted pyrimidines by a four-component coupling reaction using a functionalized silane, two types of aromatic nitriles, and an acetal is described. The efficient transformation of the pyrimidine framework consisting of an isoxazolyl ring and an ethoxy group to the 1,3,8-triazanaphthalene skeleton also proceeded in nearly quantitative yield.