An Overview of the Chemistry and Pharmacological Potentials of Furanones Skeletons

Amino acid- and peptide-conjugated heterocyclic compounds: A comprehensive review of Synthesis Strategies and biological activities

Amino acids and peptides have long been recognized as promising candidates for therapeutic development due to their unique structural properties and high specificity. However, their clinical application is often limited by rapid enzymatic degradation, poor bioavailability, and suboptimal pharmacokinetics. Conjugating these biomolecules with heterocyclic compounds has emerged as a transformative strategy to enhance their stability, bioavailability, and overall therapeutic efficacy. This review highlights significant advancements since 2000 in the synthesis and biological applications of amino acid- and peptide-conjugated heterocyclic compounds These conjugates are categorized based on their nitrogen-, sulfur-, and oxygen-containing heterocyclic cores. Key synthetic methodologies, including amide bond formation, carbon-heteroatom coupling, and carbon-carbon bond formation, are discussed in detail. These conjugates exhibit enhanced pharmacological properties, with notable applications in antimicrobial, anticancer, and anti-inflammatory treatments. Despite these advancements, challenges such as synthetic complexity and potential toxicity remain. Future research should prioritize refining synthetic methodologies and leveraging underexplored heterocycles to unlock broader therapeutic applications. Peptide-heterocycle conjugates represent a promising approach to overcoming persistent challenges in modern drug development.

PtCl2-Catalyzed Intramolecular Cyclization of α-Benzyl Allenoates to Afford Indenes and Furanones

Indene and furanone are important ring structures widely present in active pharmaceutical molecules. Here, we have developed a straightforward method for the synthesis of indene and furanone via PtCl2-catalyzed intramolecular cyclization of α-benzyl allenoates. By altering the ester substitution pattern in the α-benzyl allenoates, we can regulate the reaction site, enabling two distinct intramolecular cyclization reactions that yield both indene and furanone products, respectively. For α-benzyl-substituted ethyl allenoate, the reaction proceeds via a 5-exo cyclization to form indene derivatives. In contrast, for α-benzyl-substituted tert-butyl allenoate, the reaction involves ester hydrolysis and intramolecular cyclization, yielding furanone products. This method operates efficiently under a 5 mol % PtCl2 catalyst and exhibits good tolerance toward various functional groups. Furthermore, furanone products can be obtained on a gram scale and further smoothly converted into 1,2-disubstituted furan.

3,4-Dihalo-5-hydroxy-2(5H)-furanones: Highly Reactive Small Molecules

3,4-Dichloro-5-hydroxy-2(5H)-furanone and its dibromo analog are highly reactive molecules. Both are members of the 2(5H)-furanone family, which are important as pharmacophores present in drugs and natural products. Compounds possessing the 2(5H)-furanone skeleton isolated from plants and marine organisms exhibit bioactivity against various microorganisms and viruses and can also be used in other medical treatments. The structures of these 3,4-dihalo-2(5H)-furanones cause their high reactivity due to the presence of a carbonyl group on the C2 carbon conjugated with a double bond and a hydroxyl group on the C5 carbon. Two labile halogen atoms on carbons 3 and 4 offer additional possibilities for the introduction of other substituents. These structural features make 3,4-dihalo-5-hydroxy-2(5H)-furanones versatile reactants in chemical synthesis. In this review, we present methods of 3,4-dihalo-5-hydroxy-2(5H)-furanone synthesis, their applications as substrates in various chemical transformations, and examples of their biologically active derivatives.

Multicomponent Synthesis of 3(2H)-Furanones Initiated by Copper(II)-Catalyzed Alkyne-Carbonyl Cross Metathesis

The cooperative Lewis and Brønsted acid catalysis makes convergent synthesis of 3(2H)-furanones through a three-component coupling of 1,3-diynes, alkyl glyoxylates and water. Control experiments support that Lewis acid-catalyzed highly chemo-, regio- and stereoselective alkyne-carbonyl metathesis of 1,3-diynes and alkyl glyoxylates might be the initial step of this multicomponent annulation. Further chemo- and regioselective hydration of the alkyne-carbonyl metathesis product and subsequent oxa-Michael addition promoted by Brønsted acid results in the formation of two C-O bonds of the five-membered oxygen heterocycle.

Pyridine-catalyzed ring-opening reaction of cyclopropenone with bromomethyl carbonyl compounds toward furan-2(5H)-ones

We developed a pyridine-catalyzed annulation of diaryl cyclopropenone with bromomethyl carbonyl compounds leading to 5-carbonyl furan-2(5H)-ones. Pyridinium, derived from the reaction of bromomethyl carbonyl and pyridine, triggered the reaction by the inter-molecular Michael addition to cyclopropenone. This procedure was sensitive neither to air nor moisture and proceeded at room temperature with broad substrate scopes and good functional group tolerance in moderate-to-good yields. As such, it represents a facile and practical pathway leading to 5-carbonyl furan-2(5H)-one derivatives.

Anticancer and Apoptotic Activity in Cervical Adenocarcinoma HeLa Using Crude Extract of Ganoderma applanatum

Cancer is currently one of the foremost health challenges and a leading cause of death worldwide. Cervical cancer is caused by cofactors, including oral contraceptive use, smoking, multiparity, and HIV infection. One of the major and considerable etiologies is the persistent infection of the oncogenic human papilloma virus. G. applanatum is a valuable medicinal mushroom that has been widely used as a folk medicine for the treatment and prevention of various diseases. In this study, we obtained crude extract from G. applanatum mushroom with a subcritical water extraction method; cell viability assay was carried out and the crude extract showed an antiproliferative effect in HeLa cells with IC₅₀ of 1.55 ± 0.01 mg/mL; however, it did not show any sign of toxicity in HaCaT. Protein expression was detected by Western blot, stability of IκBα and downregulation of NFκB, IKKα, IKKβ, p-NFκB-65(Ser 536) and p-IKKα/β(Ser 176/180), suggesting loss of survival in a dose-dependent manner. RT-qPCR revealed RNA/mRNA expression; fold changes of gene expression in Apaf-1, caspase-3, cytochrome-c, caspase-9, Bax and Bak were increased, which implies apoptosis, and NFκB was decreased in a dose-dependent manner. DNA fragmentation was seen in the treatment groups as compared to the control group using gel electrophoresis. Identification and quantification of compounds were carried out by GC–MS and HPLC, respectively; 2(5H)furanone with IC₅₀ of 1.99 ± 0.01 μg/mL could be the responsible anticancer compound. In conclusion, these findings suggest the potential use of the crude extract of G. applanatum as a natural source with anticancer activity against cervical cancer.

Recyclable Catalysts for Alkyne Functionalization

In this review, we present an assessment of recent advances in alkyne functionalization reactions, classified according to different classes of recyclable catalysts. In this work, we have incorporated and reviewed the activity and selectivity of recyclable catalytic systems such as polysiloxane-encapsulated novel metal nanoparticle-based catalysts, silica-copper-supported nanocatalysts, graphitic carbon-supported nanocatalysts, metal organic framework (MOF) catalysts, porous organic framework (POP) catalysts, bio-material-supported catalysts, and metal/solvent free recyclable catalysts. In addition, several alkyne functionalization reactions have been elucidated to demonstrate the success and efficiency of recyclable catalysts. In addition, this review also provides the fundamental knowledge required for utilization of green catalysts, which can combine the advantageous features of both homogeneous (catalyst modulation) and heterogeneous (catalyst recycling) catalysis.

Allobetulone rearrangement to l8αH,19βH-ursane triterpenoids with antiviral activity

Allobetulone E-ring rearrangement under treating with HClO₄ in Ac₂O under reflux afforded new triterpenoids: 3,28-diacetoxy-21-acetyl-2(3),20(21)-18α,19βH-ursandiene 3 and 3,28-diacetoxy-2(3),18(19)-oleandiene 4. 18α,19βH-Ursanes were transformed at A- and E-rings into indolo- and bis-furfurylidene 7 derivatives. Structure elucidation was performed using COSY, NOESY, HSQC and HMBC experiments, and X-Ray analysis for 3. The potential of newly obtained 18α,19βH-ursanes was evaluated against HCMV and HPV-11, the NCI-60 cancer cell panel and inhibition of α-glucosidase. All of the compounds have shown viral inhibition towards HCMV compared to standard drug Acyclovir. 3β-Acetoxy-21β-acetyl-20β,28-epoxy-18α,19βН-ursane 1 showed moderate activity (EC₅₀ 4.87 μM) towards the HCMV-resistant isolate (GDGr K17) compared to standard drug Cidofovir and was four times more potent than Ganciclovir. Compound 7 inhibited the cell growth of the three melanoma and one colon cancer cell. 3-Oxo-21β-acetyl-20β,28-epoxy-18α,19βН-ursane 5 and compound 7 inhibited α-glucosidase with IC₅₀ 28.0 µM and 4.0 µM being from 6 to 44 times more active than acarbose.

Nanoencapsulated dietary polyphenols for cancer prevention and treatment: successes and challenges

Many dietary polyphenols have been investigated for their therapeutic potential either as single agents or in combinations. Despite the significant anticancer potential of these polyphenols in in vitro cell culture and in vivo animal models, their clinical applications have been limited because of challenges such as ineffective systemic delivery, stability and low bioavailability. Nanoencapsulation of these polyphenols could prolong circulation, improve localization, enhance efficacy and reduce the chances of multidrug resistance. This review summarized the use of various polyphenols especially epigallocatechin gallate, quercetin, curcumin and resveratrol as nanoformulations for cancer prevention and treatment. Despite some success, more research is warranted to design a nanoencapsulated combination of polyphenols, effective in in vitro, in vivo and human systems.

Photochemical rearrangement of diarylethenes: synthesis of functionalized phenanthrenes

A novel protocol for the synthesis of functionalized phenanthrenes through photocyclization of diarylethenes (DAE) under UV irradiation is proposed. The reaction proceeds through 6π-electrocyclization with the formation of a cyclic (closed) intermediate that undergoes a rearrangement affording unsymmetrical phenanthrenes in good yields. However, in contrast to benzene derivatives, the photocyclization of naphthalene diarylethenes proceeds more slowly, which is confirmed by DFT calculations. The transformation was performed on a 1 mmol scale. The scalability showed that the diarylethenes bearing oxazole, thiazole, pyrazole and imidazole as aryl moieties are more prone to photorearrangement and can be used in preparative organic synthesis.