Advancements in tetronic acid chemistry. Part 1: Synthesis and reactions

AbstractThe preparation and the properties of the elusive tetronic acid are reviewed, including its synthesis, chemical reactivity and reactions

Recent developments in the chemistry of bicyclic 6-6 systems: chemistry of pyrido[4,3-d]pyrimidines

WOS: 000381513300002The present review provides a study on the structure features, reactions and synthetic methodologies of pyrido[4,3-d]pyrimidines. 5,6,7,8-Tetrahydropyrido[4,3-d]pyrimidine and related compounds have been used as starting materials for the multi-step synthesis of tetrahydropteroic acid derivatives. The aim of this review is to give an overview of the diverse methodologies that have been reported on the chemistry of pyrido[4,3-d]pyrimidines. The different synthetic routes have been grouped according to the way the pyrido[4,3-d]pyrimidine moiety has been created. Thus, the investigated compounds were obtained from pyridine and pyrimidine derivatives or from multicomponent synthesis. The mechanistic pathways of the reactions and the important biological applications are discussed

Seven-membered Rings with Three Heteroatoms: Chemistry of 1,2,5-and 1,4,5-Thiadiazepines

WOS: 000430255400006This review describes the chemistry of 1,2,5- and 1,4,5- thiadiazepines. The investigated heterocycles are monocyclic and fused 1,2,5- and 1,4,5- thiadiazepines. The different sections cover: structural elucidation "spectroscopy", reactivity of substituents attached to ring carbon and nitrogen atoms, synthesis of monocyclic and fused heterocycles incorporated 1,2,5- and 1,4,5- thiadiazepine moiety. Nitrogen and sulfur atoms of thiadiazepine ring system have the ability to donate the electrons pairs in order to form coordination bonds forming different complexes. The aim of this review is to discuss the chemistry of title compounds up till now. The reaction mechanisms are described and discussed, as well as, the biological applications of the target compounds

Synthesis of Novel Azo Disperse dyes Derived from 4-Aminoantipyrine and their Applications to Polyester Fabrics

Abstract Nine variously substituted azo dyes derivatives 2-10 of antipyrine were prepared. The effects of the nature and orientation of the substituents on the color and dyeing properties of these dyes on polyester fibres were evaluated. The newly synthesized compounds were characterized by elemental analyses and spectral data (IR, 1 H NMR, 13 C-NMR and MS). The investigated dyes were applied t o polyester f a b r i c s and showed good light, washing, heat and acid perspiration fastness. The remarkable degree of brightness after washings is indicative of good penetration and the excellent affinity of these dyes for the fabric. The results in general revealed the efficiency of the prepared compounds as new azo dyes

Synthesis and Evaluation of Curcuminoid Analogues as Antioxidant and Antibacterial Agents

Diazocoupling reaction of curcumin with different diazonium salts of p-toluidine, 2-aminopyridine, and 4-aminoantipyrine in pyridine yielded the arylhydrazones 2a–c. Arylhydrazone of p-toluidine reacted with urea, thiourea, and guanidine nitrate to produce 5,6-dihydropyrimidines. Further reaction of 2a with 2,3-diaminopyrdine in sodium ethoxide solution yielded 1H-pyrido[2,3-b][1,4]diazepine derivative. Bis(2,5-dihydroisoxazole) is obtained from the reaction of 2a with hydroxylamine hydrochloride, while its reactions with hydrazines afforded the respective 4,5-dihydro-1H-pyrazoles. The target compounds were evaluated as antioxidant and antibacterial agents. The tested compounds showed good to moderate activities compared to ascorbic acid and chloramphenicol, respectively

Phytogenic Synthesis and Characterization of Silver Metallic/Bimetallic Nanoparticles Using <i>Beta vulgaris</i> L. Extract and Assessments of Their Potential Biological Activities

The synthesis of novel nanomedicines through eco-friendly protocols has been applied on a large scale with the prediction of discovering alternate therapies. The current work attained phytogenic synthesis of Ag-mNPs, AgSeO2-bmNPs, and Ag-TiO2-bmNPs through bio-reduction using an aqueous extract of Beta vulgaris (red beetroot). The phytochemical profile of the eco-friendly synthesized metallic/bimetallic nanoparticles was studied. The optical properties of nano-solutions were studied via UV-visible spectroscopy. The Fourier-transform infrared spectroscopy (FT-IR) spectral analyses revealed that stretching vibrations at wavenumbers 3303.81–3327.81 cm−1 attributed to phenolic hydroxyl groups documented shifts in the values in this range owing to proton dissociation through the bio-reduction of the metal ions. The surface morphology and the charge of the nanoparticles were investigated using a Transmission Electron Microscope (TEM) and zeta potential analyses. The prepared nano-solutions showed lower antioxidant activity (1,1-Diphenyl-2-picrylhydrazyl (DPPH•) and phosphomolybdate assays) than the plant extract. These results together with phytochemical analyses support the participation of the reactive species (phenolic contents) in the bio-reduction of the metal ions in the solutions through the formation of metallic/bimetallic nanoparticles. Ag-mNPs, AgSeO2-bmNPs, and Ag-TiO2-bmNPs showed antibacterial potentiality. AgSeO2-bmNPs were superior with inhibitory zone diameters of 34.7, 37.7, 11.7, and 32.7 mm against Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, and Salmonella enterica, respectively. Applying the Methylthiazole Tetrazolium (MTT) assay, the Ag-TiO2 bmNPs revealed potent cytotoxicity against the HePG2 tumor cell line (IC50 = 18.18 ± 1.5 µg/mL), while Ag-SeO2 bmNPs revealed the most potent cytotoxicity against the MCF-7 cell line (IC50 = 17.92 ± 1.4 µg/mL)

A comparative study using response surface methodology and artificial neural network towards optimized production of melanin by Aureobasidium pullulans AKW

Abstract The effect of three independent variables (i.e., tyrosine, sucrose, and incubation time) on melanin production by Aureobasidium pullulans AKW was unraveled by two distinctive approaches: response surface methodology (i.e. Box Behnken design (BBD)) and artificial neural network (ANN) in this study for the first time ever using a simple medium. Regarding BBD, sucrose and incubation intervals did impose a significant influence on the output (melanin levels), however, tyrosine did not. The validation process exhibited a high consistency of BBD and ANN paradigms with the experimental melanin production. Concerning ANN, the predicted values of melanin were highly comparable to the experimental values, with minor errors competing with BBD. Highly comparable experimental values of melanin were achieved upon using BBD (9.295 ± 0.556 g/L) and ANN (10.192 ± 0.782 g/L). ANN accurately predicted melanin production and showed more improvement in melanin production by about 9.7% higher than BBD. The purified melanin structure was verified by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction pattern (XRD), and thermogravimetric analysis (TGA). The results verified the hierarchical architecture of the particles as small compasses by SEM analysis, inter-layer spacing in the XRD analysis, maximal atomic % for carbon, and oxygen atoms in the EDX analysis, and the great thermal stability in the TGA analysis of the purified melanin. Interestingly, the current novel endophytic strain was tyrosine-independent, and the uniquely applied ANN paradigm was more efficient in modeling the melanin production with appreciate amount on a simple medium in a relatively short time (168 h), suggesting additional optimization studies for further maximization of melanin production

A Comparative Study of Cr(VI) Sorption by <i>Aureobasidium pullulans</i> AKW Biomass and Its Extracellular Melanin: Complementary Modeling with Equilibrium Isotherms, Kinetic Studies, and Decision Tree Modeling

Melanin as a natural polymer is found in all living organisms, and plays an important role in protecting the body from harmful UV rays from the sun. The efficiency of fungal biomass (Aureobasidium pullulans) and its extracellular melanin as Cr(VI) biosorbents was comparatively considered. The efficiency of Cr(VI) biosorption by the two sorbents used was augmented up to 240 min. The maximum sorption capacities were 485.747 (fungus biomass) and 595.974 (melanin) mg/g. The practical data were merely fitted to both Langmuir and Freundlich isotherms. The kinetics of the biosorption process obeyed the pseudo-first-order. Melanin was superior in Cr(VI) sorption than fungal biomass. Furthermore, four independent variables (contact time, initial concentration of Cr(VI), biosorbent dosage, and pH,) were modeled by the two decision trees (DTs). Conversely, to equilibrium isotherms and kinetic studies, DT of fungal biomass had lower errors compared to DT of melanin. Lately, the DTs improved the efficacy of the Cr(VI) removal process, thus introducing complementary and alternative solutions to equilibrium isotherms and kinetic studies. The Cr(VI) biosorption onto the biosorbents was confirmed and elucidated through FTIR, SEM, and EDX investigations. Conclusively, this is the first report study attaining the biosorption of Cr(VI) by biomass of A. pullulans and its extracellular melanin among equilibrium isotherms, kinetic study, and algorithmic decision tree modeling