Diversity-oriented sustainable synthesis of antimicrobial spiropyrrolidine/thiapyrrolizidine oxindole derivatives: New ligands for a metallo-β-lactamase from Klebsiella pneumonia

Recent advances in microwave-assisted multicomponent synthesis of spiro heterocycles

Spiro heterocycle frameworks are a class of organic compounds that possesses unique structural features making them highly sought-after targets in drug discovery due to their diverse biological and pharmacological activities. Microwave-assisted organic synthesis has emerged as a powerful tool for assembling complex molecular architectures. The use of microwave irradiation in synthetic chemistry is a promising method for accelerating reaction rates and improving yields. This review provides insights into the current state of the art and highlights the potential of microwave-assisted multicomponent reactions in the synthesis of novel spiro heterocyclic compounds that were reported between 2017 and 2023.

Recent developments on microwave-assisted organic synthesis of nitrogen- and oxygen-containing preferred heterocyclic scaffolds

In recent decades, the utilization of microwave energy has experienced an extraordinary surge, leading to the introduction of innovative and revolutionary applications across various fields of chemistry such as medicinal chemistry, materials science, organic synthesis and heterocyclic chemistry. Herein, we provide a comprehensive literature review on the microwave-assisted organic synthesis of selected heterocycles. We highlight the use of microwave irradiation as an effective method for constructing a diverse range of molecules with high yield and selectivity. We also emphasize the impact of microwave irradiation on the efficient synthesis of N- and O-containing heterocycles that possess bioactive properties, such as anti-cancer, anti-proliferative, and anti-tumor activities. Specific attention is given to the efficient synthesis of pyrazolopyrimidines-, coumarin-, quinoline-, and isatin-based scaffolds, which have been extensively studied for their potential in drug discovery. The article provides valuable insights into the recent synthetic protocols and trends for the development of new drugs using heterocyclic molecules.

Substrate-Controlled Regioselectivity Switchable [3 + 2] Annulations To Access Spirooxindole Skeletons

The additive-free [3 + 2] annulation from isatins, amino acids with 2-styrylbenzoxazoles, was described, providing a series of functional and structurally complex 3,3'-pyrrolidinyl-spirooxindole derivatives containing four contiguous and two quaternary stereogenic centers in high yields (up to 95%) and excellent diastereoselectivities (up to >25:1 dr). Interestingly, the reaction exhibits switchable regioselectivity depending on the substrate of amino acids. With proline or thioproline as the substrate, the reaction afforded α-regioselective spirooxindole skeletons. In contrast, when piperidine acid is the substrate, the reaction provided γ-regioselective spirooxindole skeletons.

Arylidenemalononitriles as Versatile Synthons in Heterocyclic Synthesis

BACKGROUND

Arylidenemalononitriles are valuable synthons for the construction of a variety of novel complex heterocyclic motifs, fused heterocycle derivatives and spirocyclic compounds. They are versatile chemical intermediates and have increasing applications in industry, agriculture, medicine, biological science.

OBJECTIVE

The aim of this review is to highlight the preparation methods and reactions of arylidenemalononitriles in the synthesis of various heterocyclic compounds.

CONCLUSION

In this review, we have presented the application of arylidenemalononitriles to construct a variety of heterocycles. Various catalysts for the preparation of arylidnemalononitriles have been described.

Engaging Isatins in Multicomponent Reactions (MCRs) - Easy Access to Structural Diversity

Multicomponent reactions (MCRs) are a valuable tool in diversity-oriented synthesis. Its application to privileged structures is gaining relevance in the fields of organic and medicinal chemistry. Isatin, due to its unique reactivity, can undergo different MCRs, affording multiple interesting scaffolds, namely oxindole-derivatives (including spirooxindoles, bis-oxindoles and 3,3-disubstituted oxindoles) and even, under certain conditions, ring-opening reactions occur that leads to other heterocyclic compounds. Over the past few years, new methodologies have been described for the application of this important and easily available starting material in MCRs. In this review, we explore these novelties, displaying them according to the structure of the final products obtained.

The application of isatin-based multicomponent-reactions in the quest for new bioactive and druglike molecules

Oxindole derivatives are known for their great interest in the field of Medicinal Chemistry, as they display vast biological activities. Recent efforts concerning the preparation of oxindole derivatives using isatin-based multicomponent reactions (MCRs) constitute a great advance in generating druglike libraries fast and with wide scaffold diversity. In this review, we address those recent developments, exploring the synthetic pathways and biological activities described for these compounds, namely antitumor, antibacterial, antifungal, antiparasitic, antiviral, antioxidant, anti-inflammatory and central nervous system (CNS) pathologies. To add new depth to this work, we used a well-established web-based free tool (SwissADME) to evaluate the most promising scaffolds in what concerns their druglike properties, namely by evaluating their compliance with some of the most valuable rules applied by medicinal chemists in both academia and industrial settings (Lipinski, Ghose, Veber, Egan, Muegge). The aim of this review is to endorse isatin-based MCRs as a valuable synthetic approach to attain new hit compounds bearing the oxindole privileged structure, while critically exploring these scaffolds' druglike properties.

Synthetic carboline compounds targeting protein: biophysical and biological perspective

Pictet-Spengler cyclization method has been adopted for the synthesis of three carboline derived compounds: two compounds with tetrahydro gama- and beta-having CF₃ group and amino alkyl chain at delta and alpha position, respectively, and another with guanidine alkyl chain at alpha-position. Structure-activity relationship of the analogues with human serum albumin was studied by fluorescence and Fourier-transform infrared spectroscopy  followed by molecular docking. The data showed maximum affinity of human serum albumin with comp7 (S0-820) followed by comp3 (S0-1040) and least with comp1 (S0-728). The compounds were tested for cytotoxic potencies. Comp3, showed maximum cytotoxicity with GI₅₀ 6.2 µM, against HCT-116, followed by comp7, and poor cytotoxicity with comp1. Comp3 and 7 induced oxidative stress mediated autophagy led programmed cell death in HCT-116. Furthermore, the compounds effectively inhibit DNA topoisomerase I activity and showed anti-inflammatory actions. In vivo studies regarding therapeutic protective action of Comp3, as a representative carboline analogue, against colon toxicant, 1,2-dimethylhydrazine dihydrochloride (DMH), showed the efficacy of the compound against organ toxicity. The existing studies on biological evaluation showed that these synthetic compounds may have a major role as anticancer agents having myriad of proven therapeutic applications. Communicated by Ramaswamy H. Sarma.

Regioselective condensation of hydroxyaromatic compounds with 2,5-dimethoxytetrahydrofuran: facile one-pot synthesis of new substituted diaryl-fused 2,8-dioxabicyclo[3.3.2]nonanes comprising central ketal moieties

Regioselective synthesis of a series of novel diaryl- and naphthyl-fused 2,8-dioxabicyclo[3.3.2]nonanes was accomplished by a one-pot reaction of p-substituted phenols and 2-naphthol with 2,5-dimethoxytetrahydrofuran.

In vitro relationship between serum protein binding to beta-carboline alkaloids: a comparative cytotoxic, spectroscopic and calorimetric assays

The work highlighted interaction of harmalol, harmaline and harmine with human serum albumin by biophysical and biochemical assays. Presence of serum protein in the media negatively affects the cytotoxicity of the alkaloids. MTT assay indicates concentration-dependent growth inhibitory effect of the alkaloids on A375, MDA-MB-231, HeLa, A549, ACHN and HepG₂ cell, having maximum cytotoxicity with GI₅₀ value of 6.5 μM on ACHN by harmine in 1% of fetal bovine serum. Detail cytotoxic studies on ACHN cell by harmine, the most cytotoxic among the three, reveal nucleosomal fragmentation, formation of comet tail, generation of reactive oxygen species, decreased mitochondrial membrane potential, up regulation of p53, caspase 3 and significant increase in G₂/M population that made the cancer cells prone to apoptosis. Furthermore, the findings unequivocally pointed out that harmine binds strongly to the protein with a binding constant of 5.53 × 10⁴ M^-1 followed by harmaline and least with harmalol. Thermodynamic results revealed enthalpy dominated, entropy favored, 1:1 binding. Molecular docking and circular dichroism suggested changed conformation of protein by partial unfolding on complexation. Further supported by infrared analysis where protein secondary structure was altered with a major decrease of α-helix from 53.68% (free protein) to 8-11% and change in β-sheet from 25.31% (free protein) to 1-6% upon binding, inducing partial protein destabilization. Site markers demonstrated site I (subdomain IIA) binding of the alkaloids to the protein. The results serve as data for the future development of serum protein-based targeted drugs. AbbreviationsCD: circular dichroism; FBS: fetal bovine serumFRETForster resonance energy transferFTIRFourier transform infraredHSAhuman serum albumin; ROS: reactive oxygen speciesCommunicated by Ramaswamy H. Sarma.

Addressing Antimicrobial Resistance through New Medicinal and Synthetic Chemistry Strategies

Over the past century, a multitude of derivatives of structural scaffolds with established antimicrobial potential have been prepared and tested, and a variety of new scaffolds have emerged. The effectiveness of antibiotics, however, is in sharp decline because of the emergence of drug-resistant microorganisms. The prevalence of drug resistance, both in clinical and community settings, is a consequence of bacterial ingenuity in altering pathways and/or cell morphology, making it a persistent threat to human health. The fundamental ability of pathogens to survive in a multitude of habitats can be triggered by recognition of chemical signals that warn organisms of exposure to a potentially harmful environment. Host immune defenses, including reactive oxygen intermediates and antibacterial substances, are among the multitude of chemical signals that can subsequently trigger expression of phenotypes better adapted for survival in that hostile environment. Thus, resistance development appears to be unavoidable, which leads to the conclusion that developing an alternative perspective for treatment options is vital. This review will discuss emerging medicinal chemistry approaches for addressing the global multidrug resistance in the 21st century.