Ring Fragmentation Research Articles

A fragmentation study of disaccharide flavonoid C‐glycosides using triple quadrupole mass spectrometry and its application for identification of flavonoid C‐glycosides in Odontosoria chinensis

RationaleFlavonoid C‐glycosides have a wide range of pharmacological activities. However, there are few mass spectrometric research on C,O‐disaccharide flavonoid C‐glycosides and di‐C,O‐saccharide flavonoid C‐glycosides. Their low‐energy collision‐induced dissociation (ESI‐CID‐MS/MS) fragmentation pattern and differences have not been reported, and the fragment ion library is incomplete. Therefore, it was essential to elucidate the fragmentation patterns of disaccharide flavonoid C‐glycosides, which is described in this study.MethodsFour disaccharide flavonoid C‐glycosides such as vitexin‐4″‐O‐glucoside were analyzed by ultra‐performance liquid chromatography‐triple quadrupole tandem mass spectrometer (UPLC‐MS/MS) using electrospray ionization (ESI) in both positive and negative ion modes. Each ion and its proposed fragmentation pathways of the four disaccharide flavonoid C‐glycosides were analyzed comprehensively. Finally, ultra‐high performance liquid chromatography‐quadrupole time‐of‐flight mass spectrometry (UPLC‐Q‐TOF‐MS/MS) and the established fragmentation patterns have been used to identify disaccharide flavonoid C‐glycosides in Odontosoria Chinensis.ResultsThe fragmentation pathways of C,O‐disaccharide flavonoid C‐glycosides and di‐C,O‐saccharide flavonoid C‐glycosides are similar. They both have the mass spectrometric characteristics of O‐glycoside and C‐glycoside. Product ions after mixed pathways of neutral fragments such as saccharide ring fragment, O‐glycosides, H2O, and CH2O elimination appeared in both types of flavonoid C‐glycosides, but their relative abundances are significantly different. According to the established fragmentation patterns, di‐C,O‐saccharide flavonoid glycosides were also found in Odontosoria chinensis.ConclusionThe fragment ions at m/z 431, 413, 341, 311, 293, and 282 in negative ion mode and m/z 293, 282, 577, 559, 541, 523, 529, and 499 in positive ion mode can serves as the main characteristics for identifying C,O‐disaccharide flavonoid C‐glycosides and di‐C,O‐saccharide flavonoid C‐glycosides.

Dissociation Without Detonation: A DFT Analysis of the Thermally Induced Fragmentation of Binary Sulfur-Nitrogen Rings and Cages.

Potential thermal dissociation pathways available to binary sulfur nitrides have been explored by density functional theory methods, and the results interpreted in terms of their known thermochemical behavior. The cyclic cation/anion pair S3N3± both undergo concerted (4 + 2) cycloreversions to afford the 3-membered thiadiazirine ring c-NSN and, respectively, the SNS± cation/anions. A similar pathway has been identified for S4N2, leading to S3 and c-NSN. More complex multistep routes for the elimination of c-NSN have been identified for the bicyclic cation/anion pair S4N5±, as well as for the neutral cage structures S4N4 and S5N6. For the S4N5+ cation a transition state for competing skeletal scrambling via a 1,3-nitrogen σ-bond shift has been located. For the multiply charged cations S3N22+ and S4N42+, dissociation mechanisms are driven by charge repulsion effects, affording SNS+/SN+ and S3N3+/SN+ respectively. Channels leading to loss of NS+ from the cyclic cation species S4N3+ and S5N5+ have also been examined, and the possible role of open-chain and cyclic S3N2-based intermediates in the formation of S2N2 during the thermal cracking of S4N4 over silver wool is explored.

Composite failure analysis of an aero-engine inter-shaft bearing inner ring

The inter-shaft bearing is a critical component in dual rotors aero-engine. Due to the complex and severe loads caused by the interactive excitation of HP and LP rotors during operation, the inter-shaft bearing is prone to damage accumulation and failure. Focusing on a typical failure of inter-shaft bearing inner ring fragmentation and cannot be spliced together completely in high thrust-weight ratio turbofan engine, this paper conducted morphological investigation, fractographic analysis, vibration signal processing, finite element numerical simulation, and fully studied the failure mechanism of this failure.The results indicated that: there exists an uncoordinated resonance speed of the HP rotor in close proximity to the operating speed. This puts the rotor in non-synchronous procession state, accompanied by the uncoordinated angular displacement of the inner and outer rings, which resulting in a lager rolling dynamic load in bearing inner ring. This further leads to high tangential impact load at the root fillet of the anti-rotation pin, causing significant stress concentration, and eventually leads to the generation of initial cracks. These cracks persist and propagate into fatigue oblique fracture over time. After oblique fracture, the modal frequencies of the inner ring become more dispersed. Under the rolling dynamic load (traveling wave load), nodal diameter vibration occurs, causing high stress vibration fatigue damage, and ultimately leading to multiple-point simultaneous fragmentation.The investigation suggests that reducing the stress levels at the root fillet of the anti-rotation pin of the inner ring is an effective approach to prevent bearing failure. This can be achieved through two methods: one is optimizing the rotor structure to decrease the rolling dynamic load on the inner ring, the other is eliminating the anti-rotation pin and appropriately reducing the tightening torque of the compression nut and the interference between the bearing inner ring and the HP turbine rear journal.

A high-rate, impact-driven biaxial fragmentation experiment for ductile materials

The experimental investigation of high strain rate fragmentation has generally been limited to one of two cases: analytically powerful but simple one-dimensional loading configurations, or complicated multiaxial experiments more closely approximating use applications. The former, exemplified by Mott-style ring fragmentation, promotes simple and confident analysis—forming the backbone of the field and revealing the basic nature of dynamic fragmentation in solids—but ignores some critical mechanisms in order to achieve that simplicity. The latter, while informing applications of interest such as ballistic impact, may provide limited insight and is often difficult to access diagnostically. This work presents an attempt to help bridge the gap between 1D ring expansion and 3D fragmentation experiments in the form of impact driven, high-strain-rate biaxial tensile fragmentation experiments. The impact target system consists of a thin specimen plate and a thick polymer impact buffer. The latter serves as a fluid-like medium allowing momentum transfer between an impacting projectile and a rapidly growing near-hemispherical bulge in the specimen plate. The deformation of the specimen and fragmentation pattern are observed using ultra-high-speed optical imaging as well as flash x-ray imaging, and individual fragments are recovered and characterized post-mortem. Using this method, the fragmentation behavior of 6061-T6 Aluminum is investigated at tensile strain rates exceeding 105s−1 and at higher stress triaxiality than that commonly achieved.

Ice template-induced assembly coupled with carbonization strategy for preparation of sulfur-doped porous carbon nanosheets from lignite as high-capacity anode for lithium-ion batteries

Two-dimensional (2D) porous carbon nanosheets with heteroatom doping are promising anode materials for lithium-ion batteries (LIBs) due to their distinctive sheet-like structure and excellent electrical conductivity. Limited by high preparation costs and cumbersome preparation processes, the large-scale production of carbon nanosheets remains a major challenge. Herein, a series of sulfur-doped porous carbon nanosheets (SCNSs) are successfully synthesized through ice template-induced assembly coupled with a carbonization approach using aromatic ring fragments exfoliating from lignite as the precursor and K2SO4 as the sulfur source. The prepared SCNSs exhibit well-defined sheet-like structures, abundant hierarchical nanopores, large specific surface areas (∼1761 m2·g−1), and high sulfur doping contents (∼7.72 at%). Such unique microstructure characteristics of SCNSs not only provide favorable and efficient channels for the lithium-ions/electrons transportation but also offer sufficient available space or active sites for lithium-ions storage. When used as anode materials for LIBs, the SCNS-3 shows high reversible capacity (1620 mAh·g−1 at 0.05 A·g−1), excellent rate performance (315 mAh·g−1 at 2 A·g−1), and superior cycling stability (901 mAh·g−1 at 1 A·g−1 after 500 cycles). Lithium storage behavior analysis indicated that the capacitance enhancement in SCNSs anodes is primarily due to improved capacitive behavior. This study provides a novel and effective route for the large-scale production of sulfur-doped carbon nanosheets using aromatic ring fragments exfoliated from lignite, which demonstrates promising industrial application potential in LIBs anode materials.

Nové nálezy z již prozkoumané lokality. Bioarcheologická analýza koster z nově objevených hrobů ze Starého Města – „Na Valách”

In the winter of 2020, a rescue archaeological excavation took place at the construction site of the Cyril and Methodius Centre of the Slovak Museum in the southern part of the well-known Middle Hillfort period burial ground ‘Na Valách’ in Staré Město. The site had been already excavated in the 1940s and 1950s. Nevertheless, several new graves were found. The purpose of this article is to present these new findings to the scientific community. Graves H 1/2020 to H 4/2020 were discovered in relatively close proximity to each other, while four other graves (H 5/2020 – H 8/2020) were located separately. These graves were all situated on the periphery of the late 1940s and Unfortunately, most of the graves were damaged during the machine excavation, which was subsequently reflected in the degree of preservation of the skeletons. In total, nine human skeletons were discovered in seven grave pits. The anthropological analysis identified three adults (one male and two females aged 40–60, 20–30, and 45–55 years) and six non-adults. Three of the immature individuals died between the ages of 15 and 17, one child was about 3 years old, and the two other children were 8–9 years old. Despite the young age (and presumably higher social status) of most of the individuals, many pathologies were found in their skeletons. The graves are dated from the second half of the 9th century to the beginning of the 10th century. Except for grave H 5/2020, all the other graves yielded rich finds (earrings, a ring, spherical buttons, knives, and ceramic fragments). The nature of the finds indicates that the graves belonged to representatives of the upper social class of early medieval Moravia in the second half of the 9th century.

Sarcocinerenolides A, an open-loop decarbonizing cembranolide, and sarcocinerenolides B–I, eight polyoxygenated cembranolides with anti-thrombotic activity from the South China Sea soft coral Sarcophyton cinereum

A previously undescribed open-loop decarbonizing cembranolide, sarcocinerenolide A, and eight undescribed cembranolides, sarcocinerenolides B–I, characterized by poly-membered oxygen ring fragments were isolated from the soft coral Sarcophyton cinereum collected from the South China Sea. The structures and absolute configurations of these previously undescribed compounds were precisely determined by analysis of NMR data, DP4+ and ECD spectra. The bioactivities of the compounds were evaluated using zebrafish models and sarcocinerenolides C and H exhibited anti-thrombotic activity.

4-hydroxyquinolin-2(1H)-one isolated in cryogenic argon and xenon matrices: Tautomers and photochemistry

4-Hydroxyquinolin-2(1H)-one (4HQ2O) was synthesized, isolated in cryogenic matrices (argon and xenon), and studied by infrared spectroscopy. Quantum chemical calculations carried out at the DFT(B3LYP)/6–311++G(3df,3pd) level of theory were used to determine the conformational and tautomeric properties of the molecule. Two tautomeric forms were identified in the as-deposited matrices with the help of the theoretical data. To investigate the photochemistry of the compound, in situ broadband ultraviolet (λ > 283 nm) irradiation of the as-deposited argon matrix was performed. This irradiation led to the generation of an additional tautomer, together with the products of fragmentation of the heterocyclic ring of the molecule, specifically isocyanic acid and carbon monoxide. Photoproducts such as 1,3-dihydro-2H-indol-2-one and cyclohepta-1,2,4,6-tetraene were also observed in the photolyzed argon matrix. A comprehensive assignment of the infrared spectra of all the species observed experimentally is presented.

Carbazole-containing covalent triazine frameworks for efficient hydrogen peroxide photosynthesis from natural sunlight

Hydrogen peroxide (H2O2) photosynthesis via polymer photocatalysts is an environmentally friendly and sustainable method for H2O2 production. However, their efficiency is currently unsatisfactory due to limited dissociation and insufficient migration of photogenerated charge carriers. Constructing donor–acceptor (D-A) type polymer photocatalysts has been demonstrated to be a promising approach to improve their optical and electronic properties related to charge carrier separation and migration. Herein, we design two donor–acceptor (D-A) type carbazole-containing covalent triazine frameworks (CTF-PCZs), namely CTF-BPCZ and CTF-TPCZ. These CTF-PCZs are found to reduce the exciton binding energy (Eb) and enhance charge carriers transfer ability compared to non-D-A type CTF-HUST-1. Remarkably, CTF-TPCZ exhibit excellent H2O2 photosynthesis performance, achieving a rate of up to 10331 μmol g−1 h−1 from pure water under solar simulator (AM 1.5G), and 6039 μmol g−1 h−1 from pure water under natural sunlight irradiation in scaled-up photocatalytic experiments, significantly surpass those of all previously reported polymer-based photocatalysts. In-situ experiments provide direct evidence for intermediates involved in the photocatalytic process. Both experiments and DFT calculations reveal that the triazine ring fragment plays a crucial role in H2O2 photosynthesis through a two-step single-electron oxygen reduction reaction (ORR) and the carbazolyl group plays a crucial role in one-step two-electron water oxidation reaction (WOR).

Making and Breaking Helical Open-Chain Oligopyrroles.

Closed-chain oligopyrroles such as porphyrins or corroles have been well-established in literature and experience a steadily strong interest by several fields of science. However, their open-chain derivatives are comparatively underrepresented, despite their intriguing properties and promising applications. Here, we aim to review typical synthetic routes, as well as point towards several emergent properties, marking them as interesting candidates for various fields of study. The review focuses on two traditional methods (each starting from highly symmetric metalloporphyrins) and then expands its scope towards more recent variations before moving on to more exotic and recent highlights that have yet to be included into the canon. Key chemical reactivities (ring closure, substitution and fragmentation) are then followed by notable physicochemical properties, placing special emphasis on potential uses in molecular electronics and sensors.

Rationalization of Ring Fragmentation Data via Simple Kinetic Energy Analysis

The available data on fragmentation of alloy rings at high strain rate has been reviewed and analysed with reference to a classical statistical and energetic model. The data have also been compared to a simple calculation based on the specific kinetic energy of the ring. It is shown that fragmentation data for alloys with over a 20 times difference in strength and 7 times difference in density scatter around a single curve when plotted as a function of specific kinetic energy over a wide range of strain rates. A fit to this curve therefore provides an approximate estimate of the expected fragment number for any ductile metal without requiring any detailed knowledge about the constitutive behaviour or defect population. This fit is better than a prediction based on the classical statistical model, and similar to that for the energetic model, which also requires a knowledge of the fragmentation fracture energy. The observation that specific kinetic energy alone can explain much of the difference observed between alloys suggest that the energy in the system is more important that details of the alloy microstructure or properties in controlling the number of fragments for a material that fails by ductile fracture. The fit does not work for a case where one alloy was heat treated to a condition where brittle failure occurred.

Early Iron Age hoard from Jodłowno, Northern Poland

The hoard from Jodłowno, near Gdańsk, about 27 km from the coast of the Baltic Sea in northern Poland, was found in 2021. The hoard, comprising 68 metal artefacts, was accidentally discovered during an authorised metal detector survey in the area. Its upper part was disturbed upon discovery, but the lower one has remained intact, enabling the reconstruction of the finds’ position within the deposit. The hoard included four cast hollow ankle rings, six bow-shaped neck rings, two pieces of casting waste, three neck ring and bracelet fragments, four forged blades and fragments, and forty-nine cast metal bars. The paper aims to present this unique find assemblage from Poland and the results of the first attempt at reconstructing the production methods of certain artefacts by analysing the traces on their surfaces.

Traction suture fixation technique using a capsular tension ring fragment for severe lens displacement during cataract surgery in dogs.

To describe the traction suture fixation technique for severely displaced lenses (≥180°) using a capsular tension ring (CTR) fragment during cataract surgery in dogs, and to retrospectively investigate its clinical outcomes. Eight dogs (nine eyes). The medical records of dogs with severe lens displacement (≥180°) due to cataracts that underwent traction suture fixation during cataract surgery using a CTR fragment at the Grand Animal Hospital (Hyogo, Japan) between November 2019 and September 2022 were retrospectively reviewed. The retrieved data included the signalment, type of CTR, and postoperative outcomes. A single CTR fragment was used to fix the capsular bag to the sclera in six eyes, and two CTR fragments were used at two sites in three eyes. The lengths of the CTR fragments used were 1 one-fifth fragment, 3 one-fourth fragments, and 8 one-third fragments. Postoperative complications included uveitis (nine eyes), glaucoma (one eye), posterior iris adhesion (one eye), corneal ulcer (one eye), and intracorneal stromal hemorrhage (one eye). Vision was maintained in all dogs during the follow-up period (2 months to 2 years and 8 months) without recurrent capsular bag displacement. This technique can correct and stabilize capsular bag displacement relatively easily through a small incision during cataract surgery in dogs with severe lens displacement. Intraocular lens implantation was also possible.

Influence of inertinite on coal physicochemical thermal transformation properties and liquefaction behaviors

Coal is heterogeneous, but the inertinite in coal is not conducive to liquefaction, resulting in a lower yield of coal-liquefied oil. Herein, to investigate the liquefaction performance of inertinite, two coal samples with different inertinite contents were obtained by the floating and sinking of coal: low-density inertinite (LDI) and high-density inertinite (HDI). Respectively, the pyrolysis characteristics and liquefaction properties of inertinite in raw coal, LDI and HDI were investigated using molecular structural models combined with quantum chemical calculations, thermogravimetric analysis (TGA), X-ray diffraction (XRD) and liquefaction tests. Quantum chemical calculations revealed that raw coal and LDI comprised more bonds with longer bond lengths and smaller bond orders than HDI. Form Bond-breaking analysis, various cyclic fragments of free radicals were obtained from the pyrolysis of raw coal were primarily monocyclic and bicyclic free radicals, the LDI were primarily binary and ternary annular fragments, and the HDI were mainly composed of quaternary ring fragments. The TGA results revealed that the thermal decomposition reactivity of LDI was comparable to raw coal and superior to HDI. XRD results revealed that the size and content of the aromatics in raw coal residue (RCR) and LDI and LDI residue (LDIR) increased in comparison with raw coal and LDI after liquefaction. The comparison of the liquefaction results of raw coal LDI and HDI revealed that coals with LDI instead of HDI exhibit better liquefaction performance.

Expanding Bioactive Fragment Space with the Generated Database GDB-13s.

Identifying innovative fragments for drug design can help medicinal chemistry address new targets and overcome the limitations of the classical molecular series. By deconstructing molecules into ring fragments (RFs, consisting of ring atoms plus ring-adjacent atoms) and acyclic fragments (AFs, consisting of only acyclic atoms), we find that public databases of molecules (i.e., ZINC and PubChem) and natural products (i.e., COCONUT) contain mostly RFs and AFs of up to 13 atoms. We also find that many RFs and AFs are enriched in bioactive vs inactive compounds from ChEMBL. We then analyze the generated database GDB-13s, which enumerates 99 million possible molecules of up to 13 atoms, for RFs and AFs resembling ChEMBL bioactive RFs and AFs. This analysis reveals a large number of novel RFs and AFs that are structurally simple, have favorable synthetic accessibility scores, and represent opportunities for synthetic chemistry to contribute to drug innovation in the context of fragment-based drug discovery.

NEW HYBRID STRUCTURES BASED ON MEMANTHINE AND EDARAVONE MOLECULES

New hybrid structures based on memantine and edaravone molecules, in which the pyrazolone ring and adamantane fragments are linked by an alkyl linker, have been synthesized. It was found that in addition to the ability to block the intrachanal site of NMDA receptors, new hybrid compounds exhibit the property of blockers of the allosteric site of NMDA receptors, which is not inherent in memantine and edaravone preparations. The most active hit compound was determined, which, along with the properties of a two-site blocker of the NMDA receptor, exhibits a pronounced activity as an inhibitor of lipid peroxidation, similar to the drug edaravone.

Polyphenylenepyridines Based on Acetylaromatic Compounds

Nitrogen-containing polyphenylene type polymers containing pyridine rings were synthesized. The polymer-forming reaction is based on the interaction of diacetylarylene and triethylorthoformate with the formation of a pyrylium salt and subsequent treatment of the intermediate product with ammonia. The optimal ratios of the reagents for the formation of the pyridine fragment were determined. The mechanism of the main reaction is discussed. The formation of the pyridine ring and phentriyl (1,3,5-triphenylsubstituted benzene) fragments was confirmed using 1H NMR data of the example of model reactions. After heating at a temperature of 450 °C, when a more complete polycondensation process occurs, the polymers reach high values of thermal characteristics—10% weight loss in an inert atmosphere corresponds to 600 °C. The structure of the synthesized polymers was confirmed using elemental analysis, IR, XPS, and EPR spectroscopy. The conjugation length in cross-linked polyphenylene pyridines can be controlled by varying the arylene bridge groups between the phentriyl fragments, which opens up opportunities for the development of new composite materials for electrical applications.

Linkage Microenvironment of Azoles‐Related Covalent Organic Frameworks Precisely Regulates Photocatalytic Generation of Hydrogen Peroxide

AbstractArtificial H2O2 photosynthesis by covalent organic frameworks (COFs) photocatalysts is promising for wastewater treatment. The effect of linkage chemistry of COFs as functional basis to photoelectrochemical properties and photocatalysis remains a significant challenge. In this study, three kinds of azoles‐linked COFs including thiazole‐linked TZ‐COF, oxazole‐linked OZ‐COF and imidazole‐linked IZ‐COF were successfully synthesized. More accessible channels of charge transfer were constructed in TZ‐COF via the donor‐π‐acceptor structure between thiazole linkage and pyrene linker, leading to efficient suppression of photoexcited charge recombination. Density functional theory calculations support the experimental studies, demonstrating that the thiazole linkage is more favorable for the formation of *O2 intermediate in H2O2 production than that of the oxazole and imidazole linkages. The real active sites in COFs located at the benzene ring fragment between pyrene unit and azole linkage.

Linkage Microenvironment of Azoles-Related Covalent Organic Frameworks Precisely Regulates Photocatalytic Generation of Hydrogen Peroxide.

Artificial H2 O2 photosynthesis by covalent organic frameworks (COFs) photocatalysts is promising for wastewater treatment. The effect of linkage chemistry of COFs as functional basis to photoelectrochemical properties and photocatalysis remains a significant challenge. In this study, three kinds of azoles-linked COFs including thiazole-linked TZ-COF, oxazole-linked OZ-COF and imidazole-linked IZ-COF were successfully synthesized. More accessible channels of charge transfer were constructed in TZ-COF via the donor-π-acceptor structure between thiazole linkage and pyrene linker, leading to efficient suppression of photoexcited charge recombination. Density functional theory calculations support the experimental studies, demonstrating that the thiazole linkage is more favorable for the formation of *O2 intermediate in H2 O2 production than that of the oxazole and imidazole linkages. The real active sites in COFs located at the benzene ring fragment between pyrene unit and azole linkage.

Concise Total Syntheses of (+)‐Brefeldin A, Diastereomers and Analogs and Their Biological Activity

AbstractBrefeldin A is an important natural product and biochemical tool with cell‐modulating and other diverse biological activities. To explore its chemical space, a generally applicable strategy for total syntheses of naturally occurring (+)‐brefeldin A (BFA), 2‐epi‐BFA, their diastereomers and analogs with varying macrocyclic ring size is reported. The five‐membered ring fragment was constructed by a short three‐step sequence consisting of tandem nucleophilic epoxide opening/Brook rearrangement/radical oxygenation and subsequent thermal radical cyclization based on the persistent radical effect. Further key steps are asymmetric aldehyde vinylation, which enables control of the absolute configuration at the allylic hydroxy group of BFA, cross‐metatheses reactions for attachment of the northern and southern side chains to the cyclopentane unit and final Shiina macrolactonization. The cytotoxic activity of all compounds was determined, and several analogs proved to be similarly active as BFA, providing insight about regions of the skeleton that can be varied or have to be conserved with respect to their biological activities. Fluorescence microscopy revealed that BFA and some non‐natural analogs disassemble the Golgi apparatus in cells with large variation of the disassembly and subsequent reassembly times.