Search Results (19)

We report the first syntheses—from commercially available 3-chloro-2-fluoroprop-1-ene (9)—of key garlic-derived compounds containing sp²-fluorine. We also report synthesis of fluoro-5,6-dihydrothiopyrans by trapping 2-fluorothioacrolein (15). Thus, difluoroallicin (12, S-(2-fluoro-2-propenyl) 2-fluoroprop-2-ene-1-sulfinothioate) is prepared by peracid oxidation of 1,2-bis(2-fluoro-2-propenyl)disulfane (11). S-2-Fluoro-2-propenyl-l-cysteine (2-fluorodeoxyalliin, 13), synthesized from cysteine and characterized by X-ray crystallography, is oxidized to its S-oxide, 2-fluoroalliin (22). The latter, with alliinase-containing powdered fresh garlic, gives a mixture of 12, allicin (1), and isomers of monofluoroallicin (23), indicating that 22 serves as a substrate for garlic alliinase. Upon heating, 12 generates transient 15, which dimerizes giving difluoro vinyl dithiins 6 and 7. Ethyl acrylate trapping of 15 affords 5- and 6-substituted 3-fluoro-5,6-dihydro-4H-thiopyrans (19 and 20). In 1,1,1,3,3,3-hexafluoro-2-propanol (HEFP) as solvent, 12 is converted into trifluoroajoene ((E,Z)-1-(2-fluoro-3-((2-fluoro-2-propenyl)sulfinyl)prop-1-en-1-yl)-2-(2-fluoro-2-propenyl)disulfane; 18). Liquid sulfur converts 11 to a (CH₂=CFCH₂)₂S_n mixture (n = 4–15), characterized by UPLC-(Ag⁺)-coordination ion spray-mass spectrometry. Full article

An organolithium reagent containing a 5,6-dihydro-1,4-dithiin moiety has been herein used as homologating agent to build up a fully protected divinylcarbinol by two different synthetic procedures, respectively, based on a step-by-step approach or a tandem process. The resulting molecule contains two double bonds masked by two dithiodimethylene bridges that can be stereoselectively removed to give a E,E- or Z,Z-configured divinylcarbinol. These products could then be conveniently functionalized, for example, with hydroxyl or amino functions, for the construction of the skeleton of more complex systems. Full article

We examine the impact of temperature (T) on the Seebeck coefficient S, i.e., the T dependence of S for a single-component molecular conductor [Pd(dddt)₂] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) with a half-filled band, where the coefficient is obtained from a ratio of the thermal conductivity to the electrical conductivity. The present paper demonstrates theoretically the novel result of large anisotropy in the Seebeck coefficient components of three-dimensional Dirac electrons in a molecular conductor. The conductor exhibits a nodal line with the energy variation around the chemical potential and provides the density of states (DOS) with a minimum. Using a threedimensional tight-binding (TB) model in the presence of both impurity and electron–phonon (e–p) scatterings, we study the Seebeck coefficient S_y for the molecular stacking and the most conducting direction. The impact of T on S_y exhibits a sign change, where S_y > 0 with a maximum at high temperatures and S_y < 0 with a minimum at low temperatures. The T dependence of S_y suggests that the contribution from the conduction (valence) band is dominant at low (high) temperatures. Further, it is shown that the the Seebeck coefficient components for perpendicular directions S_x and S_z are much smaller than S_y and present no sign change, in contrast to S_y. These results are analyzed in terms of the spectral conductivity as a function of the energy ϵ close to the chemical potential μ. Full article

The absolute configuration and stability of two thianthrene chiral sulfoxides has been determined by means of X-ray single-crystal structure determinations. The analyses and configurations allow verification that the diastereomeric sulfoxides are stable in solution and are not interconverting, which has been suggested in some studies of sulfoxides. The two thianthrene sulfoxides have slightly different R_f values, which allowed their separation using flash chromatography on silica. The spots run back-to-back, which posed a challenge for their separation. The pure, separated compounds in solution remain as separate, single spots on a Thin Layer Chromatography (TLC) plate. Full article

Little is known about how Indian farming practices affect German chamomile (Matricaria chamomilla L.). This study examines the effects of the sowing date and spacing of plants on flower productivity, essential oil concentration, and the composition of German chamomile grown in the arid zone of Rajasthan, India. In a factorial randomized block design (FRBD), the treatments consisted of four sowing dates (15 and 25 October, 5 and 15 November) and three spacings of plants (20 × 10 cm, 30 × 10 cm, and 40 × 10 cm). The dried flower yield (Kg ha⁻¹), fresh flower yield (Kg ha⁻¹), and number of flowers per plant of chamomile crop were significantly affected by the varying spacing of plants and the date of sowing. The highest values for dry weight, fresh weight, and number of flowers were obtained from the second date of sowing (25 October) with 40 × 10 cm geometry. Likewise, the highest values for total oil (12.44%) and essential oil (0.94%) contents were also obtained from the D2P3 combination (D2—sowing date 25 October, P3—40 × 10 cm spacing of plants). GC/MS analyses of the samples showed that p-menth-1-en-4-ol, acetate, cis-alpha-farnesene, anethole+estragol, 1,4-cyclohexadiene,1-methyl-4-(1-methylethyl)- and 3,6-dihydro-4-(4-methyl-3-pentenyl)-1,2-dithiin were the main identified compounds in the essential oil of chamomile fresh flowers. The treatments altered the quality profile of the essential oils in general. The principal components of chamomile essential oil were significantly affected by the D2P3 treatment. The findings of this study add to our understanding of how to grow high-quality chamomile flowers in arid regions. Full article

1,4-Bis(p-tolylamino)-6,7-dichloroanthraquinone 1 when reacted with di(sodiothio)-maleonitrile 2 afforded heterocyclic thianone compound, 5,12-dioxo-5,12-dihydroanthro[2,3-b][1,4]dithiine-2,3-dicarbonitrile 3. Using lithium/pentanol and acetic acid, the dicarbonitrile product 3 was cyclotetramerized, yielding the matching tetra 5,12-dioxo-5,12-dihydroanthro[2,3-b][1,4]dithiine-porphyrazine dye compound (2H-Pz) 4a. The dicarbonitrile molecule was a ring-shaped metallic product utilizing metallic salt and quinoline, yielding the corresponding tetra 5,12-dioxo-5,12-dihydroanthro[2,3-b][1,4]dithiine-porphyrazinato-metal II dyes (M-Pz), M = Zn, Co, or Ni 4b–d. The produced compounds’ elemental analysis investigation, Infrared, and nuclear magnetic resonance spectrum information accord with the structures attributed to them. The cyclotetramerization and complexation reactions are ensured by the molecular weight and metal load of the produced products. The inclusion of electron-donating groups resulted in a lower optical band gap of the produced dye sensitizers, with “push–pull” promotion of about 1.55 eV. The prepared substituted porphyrazines reveal high absorption in the UV–VIS region, which could be of potential value as a building block for novel electronic and optical materials as well as a sensor for technology. This is considered for improving solar cell absorption. The absorption bands of the synthesized porphyrazine dyes extend beyond 800 nm, so these dyes could be useful in various optoelectronic applications. Full article

Allium sativum L., also known as garlic, is a perennial plant widely used as a spice and also considered a medicinal herb since antiquity. The aim of this study was to determine by gas chromatography–mass spectrometry (GC–MS) the chemical profile fingerprint of the essential oil (EO) of one accession of Peruvian A. sativum (garlic), to evaluate its antioxidant activity and an in- silico study on NADPH oxidase activity of the volatile phytoconstituents. The antioxidant activity was tested using DPPH and β-carotene assays. An in-silico study was carried out on NADPH oxidase (PDB ID: 2CDU), as was ADMET prediction. The results indicated that diallyl trisulfide (44.21%) is the major component of the EO, followed by diallyl disulfide (22.08%), allyl methyl trisulfide (9.72%), 2-vinyl-4H-1,3-dithiine (4.78%), and α-bisabolol (3.32%). Furthermore, the EO showed antioxidant activity against DPPH radical (IC₅₀ = 124.60 ± 2.3 µg/mL) and β-carotene bleaching (IC₅₀ = 328.51 ± 2.0). The best docking score on NADPH oxidase corresponds to α-bisabolol (ΔG = −10.62 kcal/mol), followed by 5-methyl-1,2,3,4-tetrathiane (ΔG = −9.33 kcal/mol). Additionally, the volatile components could be linked to the observed antioxidant activity, leading to potential inhibitors of NADPH oxidase. Full article

The novel SH2-containing protein 3 (NSP3) is an oncogenic molecule that has been concomitantly associated with T cell trafficking. However, its oncological role in lung cancer and whether it plays a role in modulating the tumor immune microenvironment is not properly understood. In the present in silico study, we demonstrated that NSP3 (SH2D3C) is associated with advanced stage and poor prognoses of lung cancer cohorts. Genetic alterations of NSP3 (SH2D3C) co-occurred inversely with Epidermal Growth Factor Receptor (EGFR) alterations and elicited its pathological role via modulation of various components of the immune and inflammatory pathways in lung cancer. Our correlation analysis suggested that NSP3 (SH2D3C) promotes tumor immune evasion via dysfunctional T-cell phenotypes and T-cell exclusion mechanisms in lung cancer patients. NSP3 (SH2D3C) demonstrated a high predictive value and association with therapy resistance in lung cancer, hence serving as an attractive target for therapy exploration. We evaluated the in silico drug-likeness and NSP3 (SH2D3C) target efficacy of six organosulfur small molecules from Allium sativum using a molecular docking study. We found that the six organosulfur compounds demonstrated selective cytotoxic potential against cancer cell lines and good predictions for ADMET properties, drug-likeness, and safety profile. E-ajoene, alliin, diallyl sulfide, 2-vinyl-4H-1,3-dithiin, allicin, and S-allyl-cysteine docked well into the NSP3 (SH2D3C)-binding cavity with binding affinities ranging from −3.5~−6.70 Ă and random forest (RF) scores ranging from 4.31~5.26 pKd. In conclusion, our study revealed that NSP3 is an important onco-immunological biomarker encompassing the tumor microenvironment, disease staging and prognosis in lung cancer and could serve as an attractive target for cancer therapy. The organosulfur compounds from A. sativum have molecular properties to efficiently interact with the binding site of NSP3 and are currently under vigorous preclinical study in our laboratory. Full article

We report the structural and physical properties of a new organic Mott insulator (BEDT-BDT)AsF₆ (BEDT-BDT: benzo[1,2-g:4,5-g′]bis(thieno[2,3-b][1,4dithiin). This AsF₆ salt has the same structure as the PF₆ salt. Although the anions are disordered, the donor molecules form a θ-type arrangement. The temperature dependence of the resistivity exhibits semiconducting behavior. The static magnetic susceptibility follows Curie–Weiss law over a wide temperature range; however, below 25 K, the magnetic susceptibility is in agreement with a one-dimensional chain model with the exchange coupling J = 7.4 K. No structural phase transition was observed down to 93 K. At 270 K, the Fermi surface calculated by the tight-binding approximation is a two-dimensional cylinder; however, it is significantly distorted at 93 K. This is because the dihedral angles between the BEDT-BDT molecules become larger due to lattice shrinkage at low temperatures, which results in a smaller transfer integral (t₁) along the stack direction. This slight change in the dihedral angle gives rise to a significant change in the electronic structure of the AsF₆ salt. Radical-cation salts using BEDT-BDT, in which the highest occupied molecular orbital does not have a dominant sign throughout the molecule, are sensitive to slight differences in the overlap between the molecules, and their electronic structures are more variable than those of conventional θ-type conductors. Full article

A single-component molecular crystal [Pd(dddt)₂] has been shown to exhibit almost temperature-independent resistivity under high pressure, leading theoretical studies to propose it as a three-dimensional (3D) Dirac electron system. To obtain more experimental information about the high-pressure electronic states, detailed resistivity measurements were performed, which show temperature-independent behavior at 13 GPa and then an upturn in the low temperature region at higher pressures. High-pressure single-crystal structure analysis was also performed for the first time, revealing the presence of pressure-induced structural disorder, which is possibly related to the changes in resistivity in the higher-pressure region. Calculations based on the disordered structure reveal that the Dirac cone state and semiconducting state coexist, indicating that the electronic state at high pressure is not a simple Dirac electron system as previously believed. Finally, the first measurements of magnetoresistance on [Pd(dddt)₂] under high pressure are reported, revealing unusual behavior that seems to originate from the Dirac electron state. Full article

The de novo synthesis of piperidine nucleosides from our homologating agent 5,6-dihydro-1,4-dithiin is herein reported. The structure and conformation of nucleosides were conceived to faithfully resemble the well-known nucleoside drugs Immucillins H and A in their bioactive conformation. NMR analysis of the synthesized compounds confirmed that they adopt an iminosugar conformation bearing the nucleobases and the hydroxyl groups in the appropriate orientation. Full article

In order to assess the diversity of Greek garlic (Allium sativum L.) landraces, 34 genotypes including commercial ones were grown in the same field and their content in organosulfur compounds, pyruvate, total sugars, and total phenolics, alongside antioxidant capacity, was determined. The organosulfur compounds were studied by Gas Chromatography–Mass Spectrometry (GC–MS) after ultrasound-assisted extraction in ethyl acetate, identifying 2-vinyl-4H-1,3-dithiin and 3-vinyl-4H-1,2-dithiin as the predominant compounds, albeit in different ratios among genotypes. The bioactivity and the polar metabolites were determined in hydromethanolic extracts. A great variability was revealed, and nearly one-third of landraces had higher concentration of compounds determining bioactivity and organoleptic traits than the imported ones. We recorded strong correlations between pyruvate and total organosulfur compounds, and between antioxidant capacity and phenolics. In conclusion, chemical characterization revealed great genotype-dependent variation in the antioxidant properties and the chemical characters, identifying specific landraces with superior traits and nutritional and pharmaceutical value. Full article

We examine an effect of acoustic phonon scattering on the electric conductivity of a single-component molecular conductor [Pd(dddt)${}_2$] (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) with a half-filled band by applying the previous calculation in a two-dimensional model with Dirac cone [Phys. Rev. B. 98, 161205 (2018)], wherethe electric transport by the impurity scattering exhibits a noticeable interplay of the Dirac cone and the phonon scattering, resulting in maximum of the conductivity with increasing temperature. The conductor shows a nodal line semimetal, where the band crossing of HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) provides a loop of Dirac points located close to the Fermi energy followed by the density of states (DOS) similar to that of a two-dimensional Dirac cone. Using a tight-binding (TB) model [arXiv:2008.09277], which was obtained using the crystal structure observed from a recent X ray diffraction experiment under pressure, it is shown that the obtained conductivity explains reasonably the anomalous behavior in [Pd(dddt)${}_2$] exhibiting temperature-independent resistivity at finite temperatures. This paper demonstrates a crucial role of the acoustic phonon scattering at finite temperatures in the electric conductivity of Dirac electrons. The present theoretical results of conductivity are compared with those of the experiments. Full article

Fried garlic oil has been widely used in traditional Chinese cuisine and, recently, has become increasingly popular in food manufacturing. In this study, the effects of different initial and final frying temperature on the flavor characteristics and sensory profile of fried garlic oil were investigated using solvent-assisted flavor evaporation (SAFE) combined with gas chromatography–mass spectrometry (GC–MS). Results showed that the content of flavor compounds changed significantly as the frying temperature was increased. The sample that was treated at an initial temperature of 115 °C and a final temperature of 155 °C contained the highest amount of thioethers and heterocycles, mainly comprising dimethyl trisulfide, diallyl disulfide, and 2-vinyl-4H-1,2-dithiin. Partial least-squares regression elucidated the sensory attributes of fried and roasted garlic, showing a high correlation with thioethers and pyrazines. Furthermore, changes in the 2,6-dimethylpyrazine, dimethyl trisulfide, and diallyl disulfide concentrations were detected every 5 °C during the frying process (initial temperature, 115 °C; final temperature, 155 °C). Dimethyl trisulfide and diallyl disulfide concentrations showed irregular, downward trends, while 2,6-dimethylpyrazine concentration exhibited an increasing trend. Full article

Single-component molecular conductors form an important class of materials showing exotic quantum phenomena, owing to the range of behavior they exhibit under physical stimuli. We report the effect of high pressure on the electrical properties and crystal structure of the single-component crystal [Ni(dddt)₂] (where dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate). The system is isoelectronic and isostructural with [Pd(dddt)₂], which is the first example of a single-component molecular crystal that exhibits nodal line semimetallic behavior under high pressure. Systematic high pressure four-probe electrical resistivity measurements were performed up to 21.6 GPa, using a Diamond Anvil Cell (DAC), and high pressure single crystal synchrotron X-ray diffraction was performed up to 11.2 GPa. We found that [Ni(dddt)₂] initially exhibits a decrease of resistivity upon increasing pressure but, unlike [Pd(dddt)₂], it shows pressure-independent semiconductivity above 9.5 GPa. This correlates with decreasing changes in the unit cell parameters and intermolecular interactions, most notably the π-π stacking distance within chains of [Ni(dddt)₂] molecules. Using first-principles density functional theory (DFT) calculations, based on the experimentally-determined crystal structures, we confirm that the band gap decreases with increasing pressure. Thus, we have been able to rationalize the electrical behavior of [Ni(dddt)₂] in the pressure-dependent regime, and suggest possible explanations for its pressure-independent behavior at higher pressures. Full article