δ-Lactones are structurally diverse natural products broadly distributed across plants, fungi, microbes, and marine organisms. Their six-membered cyclic ester scaffold, often embedded in polyketide, terpenoid, fatty acid-derived, or hybrid frameworks, underpins wide-ranging pharmacological activities, including cytotoxic, antimicrobial, antiparasitic, and anti-inflammatory effects as well as modulation of enzymes and signaling pathways. Clinically relevant examples such as lovastatin, the first FDA-approved statin, and artemisinin, a cornerstone antimalarial, highlight the therapeutic value of δ-lactone motifs. In contrast, fostriecin and leptomycin B, though unsuccessful in the clinic, inspired analog development and validated new biological targets. Recent advances in synthesis-including ring-closing metathesis, CH lactonization, asymmetric annulations, and biomimetic approaches-have streamlined access to complex δ-lactones, enabling stereocontrolled synthesis and structure-activity relationship studies. This review provides a comprehensive overview of bioactive natural δ-lactones, organized by biosynthetic origin, and emphasizes their structural diversity, biological functions, and synthetic accessibility.

Several linear and macrocyclic pentapeptide derivatives have been produced by coupling Nα-isophthalic acid 1 or Nα-isophthaloyl dichloride 2 with the appropriate sarcosine methyl esters. The corresponding Nα-isophthaloyl Sarcosyl-Sarcosine methyl ester 3 was developed by mixing 1 or 2 with sarcosine methyl ester. By hydrolyzing this with methanolic sodium hydroxide, the corresponding acid 4 was subsequently obtained. The corresponding tetrapeptide esters, Nα -isophthaloyl-bis-[Sarcosyl-Glycine ethyl ester], 5 and Nα -isophthaloyl-bis-[Sarcosyl -L-Phenylalanine methyl ester], 6, were developed by coupling the latter product 4 with another molecule of glycine ethyl ester or L-phenylalanine methyl ester. These compounds were subsequently hydrolyzed with methanolic sodium hydroxide to develop the corresponding acids, Nα-isophthaloyl-bis-[Sarcosyl–Glycine], 7 and Nα-isophthaloyl-bis-[Sarcosyl - L-Phenylalanine], 8. The corresponding cyclic pentapeptide methyl esters, Cyclo-(Nα-isophthaloyl)-bis-[Sarcosyl - Glycine]-L–Lys-(OMe), 9 and Cyclo-(Nα-isophthaloyl)-bis-[Sarcosyl-L-phenyl alanine]-L–Lys-(OMe), 10, were obtained by cyclizing tetrapeptide acids with L-lysine methyl ester. Finally, the corresponding acids Cyclo-(Nα-isophthaloyl)-bis-[Sarcosyl-Glycine]-L–Lys-(OH), 11 and Cyclo-(Nα-isophthaloyl)-bis-[Sarcosyl-L-phenyl alanine]-L–Lys-(OH), 12, were obtained by hydrolyzing methyl esters 9 and 10 with 1 N methanolic sodium hydroxide or hydrazinolyzing them with hydrazine hydrate to produce the cyclohydrazide compounds, Cyclo-(Nα-isophthaloyl)-bis-[Sarcosyl-Glycine]-L–Lys-(NHNH2), 13 and Cyclo-(Nα-isophthaloyl)-bis-[Sarcosyl-L-phenyl alanine]-L–Lys-(NHNH2), 14. KEY WORDS: Amino acids, Linear peptides, Macrocyclic pentapeptides, Nα-isophthaloyl dichloride, Sarcosine Bull. Chem. Soc. Ethiop. 2026, 40(3), 667-678. DOI: https://dx.doi.org/10.4314/bcse.v40i3.13

Efficiency and synergy of bis-urea anions for the polymerization of cyclic esters

A new series of cyclic pentapeptide candidates (7-9) was prepared via the coupling of Nα-isophthalic acid or dichloride with L-phenylalanine ester, yielding compound 3, Nα-isophthaloyl L-phenylalanine ester, which was hydrolyzed to the corresponding acid 4. Then, the Nα-isophthaloyl L-phenylalanine acid 4 was coupled with a second molecule of L-phenylalanine ester to afford tetrapeptide ester 5, which was hydrolyzed to acid 6. Moreover, cyclization of tetrapeptide acid 6, to give cyclic pentapeptide ester 7, acid 8, and hydrazide 9. The newly synthesized compounds (5-9) were characterized. KEY WORDS: Amino acids, Cyclopeptides, L-Phenylalanine, Nα-isophthaloyl-bis-peptides Bull. Chem. Soc. Ethiop. 2026, 40(2), 307-317 DOI: https://dx.doi.org/10.4314/bcse.v40i2.4

Nα-isophthalic acid 1 or Nα-isophthaloyl dichloride 2 has been coupled with the proper sarcosine methyl esters to create several linear and macrocyclic pentapeptide derivatives. The analogous Nα-isophthaloyl-bis-[sarcosine methyl ester], 3, was obtained by coupling 1 or 2 with sarcosine methyl ester. The equivalent acid 4, Nα-isophthaloyl-bis-[sarcosine], was subsequently obtained by hydrolyzing this with methanolic sodium hydroxide. The corresponding tetrapeptide ester 5, Nα-isophthaloyl-bis [sarcosyl-sarcosine methyl ester], was created by coupling the latter product 4 with another molecule of sarcosine methyl ester. This compound was then hydrolyzed with methanolic sodium hydroxide to obtain the corresponding acid 6, Nα-isophthaloyl-bis [sarcosyl - sarcosine]. The equivalent cyclic pentapeptide methyl ester 7, Nα-isophthaloyl)-bis-[sarcosyl - sarcosine]-L-Lys-OMe, was produced by cyclizing tetrapeptide acids with L-lysine methyl ester. Lastly, the corresponding acids 8 and 9, cyclo-(Nα-isophthaloyl)-bis-[sarcosyl - sarcosine]-L-Ly, and Nα-isophthaloyl)-bis [sarcosyl - sarcosine]-L-Lys-NHNH2, respectively, were obtained by hydrolyzing methyl ester 7 with 1N methanolic sodium hydroxide or hydrazinolyzing it with hydrazine hydrate. KEY WORDS: Nα-isophthaloyl dichloride, Amino acids, Linear peptides, Cyclic pentapeptides Bull. Chem. Soc. Ethiop. 2026, 40(2), 341-351 DOI: https://dx.doi.org/10.4314/bcse.v40i2.6

The Calophyllum species have gained a lot of attention for their structurally diverse secondary metabolites with potential biological activities, including antibacterial scaffolds. A detailed study done on the phytochemical profile of the Calophyllum nodosum stem bark has led to the isolation of three xanthones, trapezifolixanthone (1), caloxanthone C (2), 1-hydroxy-7-methoxyxanthone (3), and a cyclic ester, canumolactone (4). Their structures were characterised using spectroscopic techniques like NMR, MS, and IR, and the spectra were confirmed with the previous literature. The pharmacokinetic properties of the compounds were predicted using SwissADME and cross-validated using pkCSM, while molecular docking simulation against bacterial DNA gyrase was performed using Autodock Vina. All isolated compounds met the drug-likeness requirements under Lipinski’s rule, according to the ADMET predictions, showing favourable oral and gastrointestinal bioavailability and absorption. Canumolactone (4), in particular, showed the best combination of solubility, clearance, and the least amount of CYP liabilities. The molecular docking simulation revealed that trapezifolixanthone (1) gave the strongest binding affinity to DNA gyrase among all isolated compounds, surpassing the binding affinity of the standard inhibitor, BDBM50198240. The current study presents the first combined ADMET predictions and molecular docking analysis for compounds isolated from C. nodosum. The findings provide preliminary evidence of their potential as drug-like scaffolds for future pharmacological development.

Novel routes for bioproduction of delta lactone aroma compounds.

Seven new resin glycosides, ipoalbins XXII-XXVIII, from the seeds of Ipomoea alba.

Four new resin glycosides, calyjaponins I-IV, from the aerial parts of Calystegia japonica.

The shift from fossil-based to biobased feedstocks is paramount for sustainable chemical production. This work presents an efficient, catalyst-free method for synthesizing a diol-rich polyol from epoxidized castor oil. Unlike conventional acid-catalyzed methods, the presented approach minimizes undesirable side reactions, yielding a polyol with a high hydroxyl number of 6.5 per triglyceride (370 mg KOH/g) and a low oligomer content. By performing the reaction at 130°C in an overheated water-dioxane mixture, we achieved full epoxide conversion in 24 h, making the process competitive with acid-catalyzed systems. This resulting polyol, characterized by a high content of adjacent diols, was utilized to prepare novel, recyclable polyboronates with 1,4-phenylenediboronic acid. Based on NMR analysis, the stoichiometry of the reaction between the synthesized polyol and phenylboronic acid was determined. Additionally, a regioselective preference for the formation of six-membered cyclic esters with 9,10,12-trihydroxyoctadecanoates, which constitute the main fraction in the synthesized polyol, was revealed. The polymers exhibit properties of low-cross-linking-density elastomers. The dynamic covalent nature of the boronate linkages was confirmed through DMTA and stress relaxation experiments. This research establishes hydroxylated castor oil as a robust and sustainable building block for polymer materials.

ABSTRACT Inherent brittleness and limited toughness of polylactide (PLA) restrict its use in high‐performance applications. To overcome these limitations, poly(L‐lactide) (PLLA) is often blended with more ductile thermoplastics or chemically modified through copolymerization with other cyclic esters such as ε ‐caprolactone ( ε ‐CL). This article reports the study of the mechanical properties of poly(L‐lactide‐co‐ ε ‐caprolactone)/glass fiber composites produced by thermoplastic resin transfer molding (TP‐RTM) in one‐step synthesis via in situ copolymerization of L‐lactide (L‐LA) and ε ‐CL into the mold with pre‐disposed glass fibers. The influence of ε ‐CL content in the PLLA‐based copolymer matrix on the resulting mechanical properties of these composites, compared to pure PLLA/glass fiber analogues, was evaluated. Mechanical testing, including tensile, three‐point bending, and impact tests, was conducted. Composites achieved Young's modulus above 6.5 GPa and bending modulus over 10.3 GPa. An increase of 90% in the absorbed energy was observed for composites containing 30% of ε ‐CL in the matrix compared to pure PLLA‐based composites. Finally, the morphology and fracture of the composites were observed by optical microscopy, revealing a good impregnation of fibers by the matrix.

Effective polymer recycling is essential to reduce plastic pollution; catalytic polymer recycling to monomer is particularly attractive, as it could operate over multiple closed-loop cycles. Aliphatic polyesters and carbonates show properties that compete with current plastics and can be depolymerized to 6- and 7-membered cyclic ester or carbonate monomers. Nonetheless, the rules governing recycling catalyst selection are unclear. Here, Zn(II), Co(II), Mg(II), Sn(II), Ca(II), Ba(II), Y(III) and Bi(III) 2-ethyl hexanoate catalysts are compared for the chemical recycling of 6 different oxygenated polymers, in bulk, at low catalyst loadings (1:100 to 1:1000) and temperatures (90-170 °C). All metals are selective for recycling to monomer but show clear differences in rates; the Zn(II) catalyst is always the most active. Using linear free energy analysis, the depolymerization rate constant directly correlates with the metal's Lewis acidity, as assessed by its hydrolysis constant. The best catalysts comprise metals with intermediate acidity, i.e., Zn(II), Co(II) and Mg(II). The structure-activity correlation applies to polymers that have primary or secondary chain-end group alcohols, 6- or 7-atom repeat units, and those featuring ester or carbonate linkages. Eyring analysis using Zn(II), Co(II), Mg(II) and Sn(II) catalysts shows that the Zn(II) catalysts balance competing transition-state enthalpy (ΔH‡d) and entropy (ΔS‡d) demands. Density functional theory calculations of key transition states suggest that Zn(II) is particularly effective because it both activates the polymer carbonyl group and labilizes the alkoxide nucleophile. These generally applicable linear free energy relationships are important tools to minimize energy input and maximize performances in future recycling processes.

Abstract An unusual photochemical cyclization of glyoxylate esters has been described resulting in selective formation of an eight-membered lactone. Site-selective hydrogen abstraction leads to a novel C–H remote functionalization.

Abstract The metal‐catalyzed ring‐opening polymerization (ROP) of cyclic (di)esters is a key strategy for producing sustainable polyesters, yet the development of robust, efficient, and tunable catalysts remains a major challenge. Herein, we reported a series of zinc catalysts supported by poly(1H‐pyrazol‐1‐yl)methane ( C ‐scorpionate) ligands for the controlled ROP of 4,4,6,7‐tetramethyloxepane‐2,5‐dione (MeOPD), a bio‐derived γ ‐ketolactone obtained from ketoisophorone. Ligand framework optimization afforded a highly active and stable binaphthalene‐containing zinc complex, enabling the synthesis of degradable polyesters with absolute M w > 900 kDa and M n > 800 kDa. Mechanistic studies revealed that steric and electronic features of the ligand suppress catalyst aggregation and stabilize the Zn─OR species. Furthermore, the catalyst exhibited remarkable tolerance to excess alcohols, allowing for precise molar mass control even at low catalyst loadings while maintaining polymerization efficiency. Tensile testing confirmed improved mechanical properties of the resulting polyesters with increasing molar mass, while photodegradation studies demonstrated efficient UV‐triggered degradation enabled by backbone ketone functionalities. These findings offer important insights into catalyst design for next‐generation sustainable polymers.

The metal-catalyzed ring-opening polymerization (ROP) of cyclic (di)esters is a key strategy for producing sustainable polyesters, yet the development of robust, efficient, and tunable catalysts remains a major challenge. Herein, we reported a series of zinc catalysts supported by poly(1H-pyrazol-1-yl)methane (C-scorpionate) ligands for the controlled ROP of 4,4,6,7-tetramethyloxepane-2,5-dione (MeOPD), a bio-derived γ-ketolactone obtained from ketoisophorone. Ligand framework optimization afforded a highly active and stable binaphthalene-containing zinc complex, enabling the synthesis of degradable polyesters with absolute Mw>900kDa and Mn>800kDa. Mechanistic studies revealed that steric and electronic features of the ligand suppress catalyst aggregation and stabilize the Zn─OR species. Furthermore, the catalyst exhibited remarkable tolerance to excess alcohols, allowing for precise molar mass control even at low catalyst loadings while maintaining polymerization efficiency. Tensile testing confirmed improved mechanical properties of the resulting polyesters with increasing molar mass, while photodegradation studies demonstrated efficient UV-triggered degradation enabled by backbone ketone functionalities. These findings offer important insights into catalyst design for next-generation sustainable polymers.

Abstract Covalent organic frameworks (COFs) hold grand promise in chemical separations owing to their tunable pore architectures and rich functionalities. However, their practical efficacy is often plagued by disordered stacking and restricted accessibility of functional groups. In this study, we present a side‐chain engineering strategy, which synergistically manipulates pore‐wall functionalization, dynamic structural reconstruction, and bond stabilization, to fabricate hollow, stable, and polyol‐functionalized COFs (HSPCOF) adsorbents for high‐efficiency capture of boron from brine. For the first time, we demonstrate that side‐chain‐engineering can be employed to introduce polyol groups, enabling boron chelation while concurrently enhancing the crystallinity of COFs. The resultant HSPCOF exhibits a high specific surface area, interconnected channels, and exceptional boron adsorption capacity of 150.05 mg g −1 at 298 K, within 180 min, 10.29‐fold higher than commercial resin MK51. Density functional theory (DFT) simulations reveal that the HSPCOF preferentially binds borate anions via bidentate cyclic ester formation with polyol groups, affording strong affinity and high selectivity. Remarkably, HSPCOF maintains robust borate anion adsorption performance in harsh Salt Lake brine, achieving 848.79 mg g −1 capacity and 91.51% removal efficiency, validating its practical utility. This work affords generic guidelines for designing crystal and functionally precise COF materials by side‐chain engineering.

Covalent organic frameworks (COFs) hold grand promise in chemical separations owing to their tunable pore architectures and rich functionalities. However, their practical efficacy is often plagued by disordered stacking and restricted accessibility of functional groups. In this study, we present a side-chain engineering strategy, which synergistically manipulates pore-wall functionalization, dynamic structural reconstruction, and bond stabilization, to fabricate hollow, stable, and polyol-functionalized COFs (HSPCOF) adsorbents for high-efficiency capture of boron from brine. For the first time, we demonstrate that side-chain-engineering can be employed to introduce polyol groups, enabling boron chelation while concurrently enhancing the crystallinity of COFs. The resultant HSPCOF exhibits a high specific surface area, interconnected channels, and exceptional boron adsorption capacity of 150.05mg g-1 at 298K, within 180min, 10.29-fold higher than commercial resin MK51. Density functional theory (DFT) simulations reveal that the HSPCOF preferentially binds borate anions via bidentate cyclic ester formation with polyol groups, affording strong affinity and high selectivity. Remarkably, HSPCOF maintains robust borate anion adsorption performance in harsh Salt Lake brine, achieving 848.79mg g-1 capacity and 91.51% removal efficiency, validating its practical utility. This work affords generic guidelines for designing crystal and functionally precise COF materials by side-chain engineering.

The restriction of the use of antibiotics in poultry farming in many countries has fueled interest in alternative products such as herbal preparations (a group of natural products), which have been the subject of numerous studies in recent years. The aim of the study was to evaluate the effect of biologically active plant organic substances on the chemical, fatty and amino acid composition of muscles and liver of broiler chickens. The studies were performed on 125 7-day-old broiler chickens (Arbor Acres cross), divided into 5 groups (n = 25). The duration of the experiment was 42 days. The difference was that the control group received the basal diet; experimental group I – the basal diet + gamma lactone at a dose of 0.1 ml/kg of feed/day; experimental group II – the basal diet + gamma lactone at a dose of 0.1 ml/kg + cinnamaldehyde a dose of 55 mg/kg of feed/day; experimental group III – the main diet + gamma lactone at a dose of 0.1 ml/kg + 7-hydroxycoumarin at at a dose of 2 mg/kg of feed/day; experimental group IV – the main diet + gamma lactone at a dose of 0.1 ml/kg + cinnamic aldehyde at a dose of 55 mg/kg + 7-hydroxycoumarin at a dose of 2 mg/kg of feed/day. The study found that the young birds from the experimental groups exceeded their peers from the control group in fat accumulation in the pectoral muscles: I group by 0.43 %, II – by 0.88 % (P≤0.05), III – by 0.82 % (P≤0.05) and IV group – by 0.4 %. Birds from groups II and IV in terms of protein content in the femoral muscle exceeded their counterparts from the control group by 0.87 and 0.82 %, respectively. In the breast and thigh muscles of broilers of group III, fatty acids accumulated more compared to the control: palmitoleic by 0.5 and 0.3 %, stearic by 0.2 % (only in the thigh muscles), oleic by 1.1 % (P≤0.05) (only in the breast muscles), linoleic by 1.5 (P≤0.05) and 3.1 % (P≤0.01). When feeding pure gamma lactone with the diet, the highest deposition of arginine by 0.77 %, lysine by 2.64 % (P≤0.05), leucine + isoleucine by 2.1 % (P≤0.05), valine by 0.83 %, serine by 1.57 % (P≤0.05), alanine by 1.22 % (P≤0.05) in the femoral muscles was observed in relation to the control group.

Carboxylic ester hydrolases from Antarctic psychrophilic Psychrobacter strains: From genome prospecting to biotreatment of polyester plastics.

Described is a concise route to caesappins A and B, urolithin C, and protosappanin A, which share a common sappanin core. An arylation of a cyclic vinylogous ester and a brominative aromatization were applied to construct a privileged intermediate, which was subsequently converted to the target natural products through strategic coupling reactions.