Structure activity relationship (SAR) and anticancer activity of pyrrolidine derivatives: Recent developments and future prospects (A review)

An insight into recent developments in imidazole based heterocyclic compounds as anticancer agents: Synthesis, SARs, and mechanism of actions

Among all non-communicable diseases, cancer is ranked as the second most common cause of death and is rising constantly. While cancer treatments mainly include radiation therapy, chemotherapy, and surgery; chemotherapy is considered the most commonly employed and effective treatment. Most of the chemotherapeutic agents are azoles based compounds and imidazole is one such insightful azole. The anticancer properties of imidazole-based compounds have been thoroughly explored in recent years and all monosubstituted, disubstituted, trisubstituted, and tetrasubstituted imidazoles have been explored for their anticancer activities. Along with these compounds, other imidazole-based compounds like 1,3-dihydro-2H-imidazole-2-thiones, imidazolones, and poly imidazole compounds have also been explored for their anticancer activities. The activities of these compounds are heavily influenced by their structural resemblance to combretastatin 4A and ABI (2-aryl-4-benzoyl-imidazole). The lead compounds were highly active on breast, gastric, colon, ovarian, cervical, bone marrow, melanoma, prostate, lung, leukemic, neuroblastoma, liver, Ehrlich, melanoma, and pancreatic cancers. The targets of these leads like tubulin, heme oxygenases, VEGF, tyrosine kinases, EGFR, and others have also been explored. The exploration of the anticancer potential of substituted imidazole compounds is the main topic of this review including synthesis, SAR, and mechanism.

Enantioselective 1,4-Borylamination via Copper-Catalyzed Cascade Hydroborylation and Hydroamination of Arylidenecyclopropanes

Compounds bearing both boryl and amino groups at distal positions are invaluable synthons for synthesizing pharmaceuticals, drug candidates, and natural products, but their catalytic enantioselective synthesis remains rarely explored. We report the first enantioselective 1,4-borylamination reaction through a copper-catalyzed cascade hydroborylation and hydroamination of arylidenecyclopropanes. This reaction combines four readily available components in a highly chemo-, site-, and enantioselective fashion (>20:1 r.r. and up to 99% ee), yielding a diverse array of synthetically valuable enantioenriched 4-amino alkylboronates. The versatile utility of these products is highlighted by their diverse transformations and wide applications in pharmaceutical synthesis and drug discovery. Preliminary mechanistic studies were conducted to elucidate the operative reaction pathway, intermediates, and origins of its high chemo- and site-selectivity.

BW312 Hordeum vulgare semi-dwarf mutant exhibits a shifted metabolic profile towards pathogen resistance

INTRODUCTION

Plant hormonal mutants, which do not produce or are insensitive to hormones, are often affected in their growth and development, but other metabolic rearrangements might be involved. A trade-off between growth and stress response is necessary for the plant survival.

OBJECTIVES

Here, we explore the metabolic profile and the pathogen resistance of a brassinosteroid-insensitive Hordeum vulgare L. semi-dwarf mutant, BW312.

METHODS

We investigate BW312 metabolism through a chemical enrichment analysis, confirming a shifted metabolic profile towards pathogen resistance. The effective pathogen resistance of the mutant was tested in presence of Pyrenophora teres and Fusarium graminearum.

RESULTS

Four compound families were increased in the mutant (pyrrolidines, basic amino acids, alkaloids, monounsaturated fatty acids), while two compound families were decreased (pyrrolidinones, anthocyanins). Dipeptides were also altered (increased and decreased). BW312 displayed a better resistance to Pyrenophora teres in the earliest stage of infection with a 21.5% decrease of the lesion length 10 days after infection. BW312 also exhibited a reduced lesion length (43.3%) and a reduced browning of the lesions (55.5%) when exposed to Fusarium graminearum at the seedling stage.

CONCLUSION

The observed metabolomic shift strongly suggests that the BW312 semi-dwarf mutant is in a primed state, resulting in a standby state of alertness to pathogens.

Progress in the Stereoselective Synthesis Methods of Pyrrolidine-Containing Drugs and Their Precursors

The presented review systematizes and summarizes the data on the synthesis of pyrrolidine derivatives, which are precursors for obtaining drugs. Based on the analysis of published data, the most promising directions in the synthesis of biologically active compounds containing a pyrrolidine ring are identified. Stereoselective synthesis methods are classified based on the source of the pyrrolidine ring. The first group includes methods that use a pyrrolidine ring as the starting compound. The second group combines stereoselective methods of cyclization of acyclic starting compounds, which lead to optically pure pyrrolidine derivatives.

Synthesis and evaluation of tetrahydropyrrolo[1,2-a]quinolin-1(2H)-ones as new tubulin polymerization inhibitors

Here we explored new 1,5-disubstituted pyrrolidin-2-ones 1, 2 and 5-aryl-3,3a,4,5-tetrahydropyrrolo[1,2-a]quinoline-1(2H)-ones 3 as inhibitors of tubulin polymerization. We evaluated their effects on microtubule dynamics in vitro and on the proliferation of A549 cells, using flow cytometry-based cell cycle analysis. The results were verified with phase-contrast microscopy in three cancer cell lines: A549, HeLa and MCF-7. Guided by molecular modeling of the interactions between tubulin and the most active of the identified compounds, we designed, synthesized, and tested the 3-hydroxyphenyl-substituted compound 3c. This compound was further shown to bind to the colchicine site of tubulin and reduce microtubule growth rates in vitro. Moreover, compound 3c arrested division of the A549 cells in the low micromolar range (IC50 = 5.9 μM) and exhibited cytotoxicity against four different cell lines in the MTT assay for cell proliferation. Our findings demonstrate that 5-aryltetrahydropyrrolo[1,2-a]quinoline-1(2H)-one is a promising scaffold for the development of novel tubulin polymerization inhibitors.

Synthesis, in vitro biological evaluation and in silico studies of novel pyrrolidine derived thiosemicarbazones as dihydrofolate reductase inhibitors

Dihydrofolate reductase (DHFR) is a crucial enzyme involved in folate metabolism and serves as a prime target for anticancer and antimicrobial therapies. In this study, a series of 4-pyrrolidine-based thiosemicarbazones were synthesized and evaluated for their DHFR inhibitory activity. The synthesis involved a multistep procedure starting from readily available starting materials, leading to the formation of diverse thiosemicarbazone 5(a-r) derivatives. These compounds were then subjected to in vitro assays to evaluate their inhibitory potential against DHFR enzyme. The synthesized compounds 5(a-r) exhibited potent inhibition with IC50 values in the range of 12.37 ± 0.48 μM to 54.10 ± 0.72 μM. Among all the derivatives 5d displayed highest inhibitory activity. Furthermore, molecular docking and ADME studies were performed to understand the binding interactions between the synthesized compounds and the active site of DHFR. The in vitro and in silico data were correlated to identify compounds with promising inhibitory activity and favorable binding modes. This comprehensive study provides insights into the structure-activity relationships of 4-pyrrolidine-based thiosemicarbazones as DHFR inhibitors, offering potential candidates for further optimization towards the development of novel therapeutic agents.

Computational Insights into Chromene/pyran Derivatives: Molecular Docking, ADMET Studies, DFT Calculations, and MD Simulations as Promising Candidates for Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative condition characterized by both motor and non-motor symptoms. Although PD is commonly associated with a decline of dopaminergic neurons in the substantia nigra, other diagnostic criteria and biomarkers also exist. In the search for novel therapeutic agents, chromene and pyran derivatives have shown potential due to their diverse pharmacological activities. This study utilizes a comprehensive computational approach to investigate the viability of chromene/pyran compounds as potential treatments for PD. The drug-likeness characteristics of these molecules were analyzed using ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) studies. Molecular docking was performed against PDB ID: 2V5Z. The best three molecules chosen were compound 7, compound 24, and compound 67 have a binding energy of -6.7, -8.6, and -10.9 kcal/mol. Molecules demonstrating positive blood-brain barrier permeability, good solubility, and favorable binding affinity were further evaluated using Density Functional Theory (DFT) calculations and Molecular Dynamics (MD) simulations to assess their electronic structure and stability. DFT calculations indicated that molecule 82 has a dipole moment of 15.70 D. RMSD and RMSF results confirmed the stability of the complexes over a 100 ns simulation, with a maximum of 3 hydrogen bonds formed.

The Structure-Antiproliferative Activity Relationship of Pyridine Derivatives

Pyridine, a compound with a heterocyclic structure, is a key player in medicinal chemistry and drug design. It is widely used as a framework for the design of biologically active molecules and is the second most common heterocycle in FDA-approved drugs. Pyridine is known for its diverse biological activity, including antituberculosis, antitumor, anticoagulant, antiviral, antimalarial, antileishmania, anti-inflammatory, anti-Alzheimer's, antitrypanosomal, antimalarial, vasodilatory, antioxidant, antimicrobial, and antiproliferative effects. This review, spanning from 2022 to 2012, involved the meticulous identification of pyridine derivatives with antiproliferative activity, as indicated by their minimum inhibitory concentration values (IC50) against various cancerous cell lines. The aim was to determine the most favorable structural characteristics for their antiproliferative activity. Using computer programs, we constructed and calculated the molecular descriptors and analyzed the electrostatic potential maps of the selected pyridine derivatives. The study found that the presence and positions of the -OMe, -OH, -C=O, and NH2 groups in the pyridine derivatives enhanced their antiproliferative activity over the cancerous cellular lines studied. Conversely, pyridine derivatives with halogen atoms or bulky groups in their structures exhibited lower antiproliferative activity.

Influence of proline and hydroxyproline as antimicrobial and anticancer peptide components on the silver(I) ion activity: structural and biological evaluation with a new theoretical and experimental SAR approach

Silver(I) complexes with proline and hydroxyproline were synthesized and structurally characterized and crystal structure analysis shows that the formulas of the compounds are {[Ag2(Pro)2(NO3)]NO3}n (AgPro) (Pro = L-proline) and {[Ag2(Hyp)2(NO3)]NO3}n (AgHyp) (Hyp = trans-4-hydroxy-L-proline). Both complexes crystallize in the monoclinic lattice with space group P21 with a carboxylate bidentate-bridging coordination mode of the organic ligands Pro and Hyp (with NH2+ and COO- groups in zwitterionic form). Both complexes have a distorted seesaw (C2v) geometry around one silver(I) ion with τ4 values of 58% (AgPro) and 51% (AgHyp). Moreover, the results of spectral and thermal analyses correlate with the structural ones. 1H and 13C NMR spectra confirm the complexes species' presence in the DMSO biological testing medium and their stability in the time range of the bioassays. In addition, molar conductivity measurements indicate complexes' behaviour like 1 : 1 electrolytes. Both complexes showed higher or the same antibacterial activity against Bacillus cereus, Pseudomonas aeruginosa and Staphylococcus aureus as AgNO3 (MIC = 0.063 mM) and higher than silver(I) sulfadiazine (AgSD) (MIC > 0.5 mM) against Pseudomonas aeruginosa. In addition, complex AgPro exerted a strong cytotoxic effect against the tested MDA-MB-231 and Jurkat cancer cell lines (IC50 values equal to 3.7 and 3.0 μM, respectively) compared with AgNO3 (IC50 = 6.1 (5.7) μM) and even significantly higher selectivity than cisplatin (cisPt) against MDA-MB-231 cancer cell lines (SI = 3.05 (AgPro); 1.16 (cisPt), SI - selectivity index). The binding constants and the number of binding sites (n) of AgPro and AgHyp complexes with bovine serum albumin (BSA) were determined at four different temperatures, and the zeta potential of BSA in the presence of silver(I) complexes was also measured. The in ovo method shows the safety of the topical and intravenous application of AgPro and AgHyp. Moreover, the complexes' bioavailability was verified by lipophilicity evaluation from the experimental and theoretical points of view.

Chitosan-sulfonic acid-catalyzed green synthesis of naphthalene-based azines as potential anticancer agents

Aim: This study focuses on advancing green chemistry in anticancer drug discovery, particularly through the synthesis of azine derivatives with a naphthalene core using CS-SO3H as a catalyst. Methods: Novel benzaldazine and ketazine derivatives were synthesized using (E)-(naphthalen-1-ylmethylene)hydrazine and various carbonyl compounds. The methods employed included thermal and grinding techniques, utilizing CS-SO3H as an eco-friendly and cost-effective catalyst. Results: The approach resulted in high yields, short reaction times and demonstrated catalyst reusability. Cytotoxicity tests highlighted compounds 3b, 11 and 13 as potent against the HEPG2-1. Conclusion: This study successfully aligns with the objectives of eco-conscious drug development in organic chemistry. Molecular docking and in silico studies further indicate the potential of these ligands as antitumor medicines, with favorable oral bioavailability properties.

Molecular Deformation Is a Key Factor in Screening Aggregation Inhibitor for Intrinsically Disordered Protein Tau

Direct inhibitor of tau aggregation has been extensively studied as potential therapeutic agents for Alzheimer's disease. However, the natively unfolded structure of tau complicates the structure-based ligand design, and the relatively large surface areas that mediate tau-tau interactions in aggregation limit the potential for identifying high-affinity ligand binding sites. Herein, a group of isatin-pyrrolidinylpyridine derivative isomers (IPP1-IPP4) were designed and synthesized. They are like different forms of molecular "transformers". These isatin isomers exhibit different inhibitory effects on tau self-aggregation or even possess a depolymerizing effect. Our results revealed for the first time that the direct inhibitor of tau protein aggregation is not only determined by the previously reported conjugated structure, substituent, hydrogen bond donor, etc. but also depends more importantly on the molecular shape. In combination with molecular docking and molecular dynamics simulations, a new inhibition mechanism was proposed: like a "molecular clip", IPP1 could noncovalently bind and fix a tau polypeptide chain at a multipoint to prevent the transition from the "natively unfolded conformation" to the "aggregation competent conformation" before nucleation. At the cellular and animal levels, the effectiveness of the inhibitor of the IPP1 has been confirmed, providing an innovative design strategy as well as a lead compound for Alzheimer's disease drug development.

Targeted Inhibition of the PI3K/Akt/mTOR Signaling Axis: Potential for Sarcoma Therapy

Sarcoma is a heterogeneous group of malignancies often resistant to conventional chemotherapy and radiation therapy. The phosphatidylinositol-3-kinase/ protein kinase B /mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway has emerged as a critical cancer target due to its central role in regulating key cellular processes such as cell growth, proliferation, survival, and metabolism. Dysregulation of this pathway has been implicated in the development and progression of bone sarcomas (BS) and soft tissue sarcomas (STS). PI3K/Akt/mTOR inhibitors have shown promising preclinical and clinical activity in various cancers. These agents can inhibit the activation of PI3K, Akt, and mTOR, thereby reducing the downstream signaling events that promote tumor growth and survival. In addition, PI3K/Akt/mTOR inhibitors have been shown to enhance the efficacy of other anticancer therapies, such as chemotherapy and radiation therapy. The different types of PI3K/Akt/mTOR inhibitors vary in their specificity, potency, and side effect profiles and may be effective depending on the specific sarcoma type and stage. The molecular targeting of PI3K/Akt/mToR pathway using drugs, phytochemicals, nanomaterials (NMs), and microbe-derived molecules as Pan-PI3K inhibitors, selective PI3K inhibitors, and dual PI3K/mTOR inhibitors have been delineated. While there are still challenges to be addressed, the preclinical and clinical evidence suggests that these inhibitors may significantly improve patient outcomes. Further research is needed to understand the potential of these inhibitors as sarcoma therapeutics and to continue developing more selective and effective agents to meet the clinical needs of sarcoma patients.

Ampyrone appended 1,2,3-triazole as selective fluorescent Cu(II) ion sensor: DFT and docking findings

The present report describes the application of the 'Click Chemistry' pathway to synthesize a fluorescent probe (APT) based on ampyrone (4-aminoantipyrine), entailing two benzyl groups as the fluorophores coupled to the antipyrine structure through 1,2,3-triazole moieties. Infrared spectroscopy (IR), nuclear magnetic resonance (1H and 13C), and mass spectrometry were the standard spectroscopic methods used to characterize APT. The ion recognition potential of the probe was analyzed through absorption and emission spectroscopy employing a 4:1 combination of CH3CN and H2O, which demonstrated APT to be an efficient sensing agent for Cu(II) ions, wherein the absorption spectrum of the probe displayed a hypsochromic shift with a hyperchromic shift on gradually adding the metal ion solution of Cu(II), whereas quenching of the probe's fluorescence emission on Cu(II) addition was attributed to the chelation-enhanced fluorescence quenching (CHEQ), induced by the d9 electronic configuration of Cu(II). The stoichiometry of the complexation of APT with Cu(II) is indicative of a 1:1 ratio, while the detection limit (LOD) and quantification limit (LOQ) as estimated from the fluorescence titration results were 3.11 µM and 10.35 µM respectively. Furthermore, DFT analysis was also undertaken to yield the energy-optimized structures and HOMO-LUMO density plots of APT and its corresponding Cu(II) complex via the B3LYP/631G+(d,p) level of theory for APT, and LANL2DZ basis set for the APT-Cu(II) complex. Docking analysis of the probe with the synaptic vesicle protein (SV2A) gave glimpses about its anticonvulsant properties.

Part-II: an update of Schiff bases synthesis and applications in medicinal chemistry-a patent review (2016-2023)

INTRODUCTION

Schiff bases are compounds with characteristic features of azomethine linkage (-C=N-). Schiff bases are capable of coordinating with metal ions via azomethine nitrogen. Schiff base derivatives and their metal complexes are known for intriguing novel therapeutic properties. In organic synthesis, the Schiff base reaction is prime in creating the C-N bond. Synthetic accessibility and structural diversity are the salient features for facile synthesis of Schiff base hybrids via a condensation reaction between an aldehyde/ketone and primary amines.

AREA COVERED

This review aims to provide a comprehensive overview of the commendable medicinal applications of Schiff base derivatives and their metal complexes patented from 2016 to 2023.

EXPERT OPINION

Schiff base derivatives are exceptional molecules for their assorted applications in medicinal chemistry. Several Schiff base products are marketed as drugs, and plenty of room is available for the purposive synthesis of new compounds in a diverse pool of disciplines. Expansion in the derivatization of Schiff bases in innumerable directions with multitudinous applications makes them 'magical molecules.' These compounds have proved extraordinary, from medicinal chemistry to other fields outside medicine. This review covers the therapeutic importance of Schiff base derivatives and aims to cover the patents published in recent years (2016-2023).

1,2-Silyl Shift-Induced Heterocyclization of Propargyl Silanes: Synthesis of Five-Membered Heterocycles Containing a Functionalized Olefin Side Chain

Propargyl silanes with a terminal alkyne moiety undergo a 1,2-silyl shift when activated with electrophiles such as H+, Br+, I+, and PhSe+. A method was developed to trap 1,3-transposed electrophilic centers with various internal O-, N-, and S-nucleophiles in a 5-exo manner. This synthetic procedure provided five-membered heterocycles containing a trisubstituted olefin side chain. The scope of the method includes access to tetrahydrofuran, γ-butyrolactone, 2-isooxazoline, pyrrolidine, and thiolane derivatives in yields ranging from 25 to 85% (23 examples in total). Reactions with TsNBr2 ensured complete (E)-selectivity of the newly formed olefins. Further functionalization of the obtained 1-trialkylsilyl-2-bromovinyl side chain was demonstrated by double-bond geometry-preserving electrophilic substitution and cross-coupling reactions that provided heterocycles with a trisubstituted vinyl moiety.

Recent insights about pyrrolidine core skeletons in pharmacology

To overcome numerous health disorders, heterocyclic structures of synthetic or natural origin are utilized, and notably, the emergence of various side effects of existing drugs used for treatment or the resistance of disease-causing microorganisms renders drugs ineffective. Therefore, the discovery of potential therapeutic agents that utilize different modes of action is of utmost significance to circumvent these constraints. Pyrrolidines, pyrrolidine-alkaloids, and pyrrolidine-based hybrid molecules are present in many natural products and pharmacologically important agents. Their key roles in pharmacotherapy make them a versatile scaffold for designing and developing novel biologically active compounds and drug candidates. This review aims to provide an overview of recent advancements (especially during 2015-2023) in the exploration of pyrrolidine derivatives, emphasizing their significance as fundamental components of the skeletal structure. In contrast to previous reviews that have predominantly focused on a singular biological activity associated with these molecules, this review consolidates findings from various investigations encompassing a wide range of important activities (antimicrobial, antiviral, anticancer, anti-inflammatory, anticonvulsant, cholinesterase inhibition, and carbonic anhydrase inhibition) exhibited by pyrrolidine derivatives. This study is also anticipated to serve as a valuable resource for drug research and development endeavors, offering significant insights and guidance.

Sulfamidate-Based Stereoselective Total Synthesis of (+)-Preussin Using Gold(I)-Catalyzed Intramolecular Dehydrative Amination: Dead End and Detour

A sulfamidate-based stereoselective total synthesis of (+)-preussin has been developed. The key step involves a gold(I)-catalyzed intramolecular dehydrative amination of sulfamate esters tethered to allylic alcohols, which allows for the construction of the cyclic sulfamidate with high stereoselectivity. Further manipulation to highly constrained bicyclic sulfamidate and the following ring-opening process afford 3-hydroxypyrrolidine motif stereoselectively. The energy of the constrained bicyclic ring system is relieved by the subsequent ring-opening process, which leads to a stereoselective formation of the 3-hydroxypyrrolidine motif under mild reaction conditions. The success of this approach not only provides a new method for the total synthesis of enantiomerically pure (+)-preussin but also highlights the synthetic utility of sulfamidates in constructing valuable natural product architectures.

Juglans regia Linn.: A Natural Repository of Vital Phytochemical and Pharmacological Compounds

Juglans regia Linn. is a valuable medicinal plant that possesses the therapeutic potential to treat a wide range of diseases in humans. It has been known to have significant nutritional and curative properties since ancient times, and almost all parts of this plant have been utilized to cure numerous fungal and bacterial disorders. The separation and identification of the active ingredients in J. regia as well as the testing of those active compounds for pharmacological properties are currently of great interest. Recently, the naphthoquinones extracted from walnut have been observed to inhibit the enzymes essential for viral protein synthesis in the SARS-CoV-2. Anticancer characteristics have been observed in the synthetic triazole analogue derivatives of juglone, and the unique modifications in the parent derivative of juglone have paved the way for further synthetic research in this area. Though there are some research articles available on the pharmacological importance of J. regia, a comprehensive review article to summarize these findings is still required. The current review, therefore, abridges the most recent scientific findings about antimicrobial, antioxidant, anti-fungal, and anticancer properties of various discovered and separated chemical compounds from different solvents and different parts of J. regia.