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The total synthesis of 14 membered macrolide Pestalotioprolide C and C7-epi- Pestalotioprolide C were accomplished starting from commercially available D-Mannitol by Stereoselective synthetic approach. The key reactions involved are Mitsunobu reaction, Regioselective ring opening of chiral epoxide and ring-closing metathesis reactions (RCM). [ABSTRACT FROM AUTHOR]

Oil is the "blood" and economic lifeblood of modern industry, but traditional light crude oil has been over-consumed, and it has been difficult to meet human demand for energy, so the exploitation of heavy oil is particularly important. In this paper, an oil-soluble catalyst was synthesized to catalyze the pyrolysis reaction of heavy oil in collaboration with reservoir minerals, so as to achieve efficient viscosity reduction of heavy oil and reduce production costs. The experimental results showed that Zn(II)O + K had the best synergistic viscosity reduction effect after the aquathermolysis of No. 1 oil sample under the reaction conditions of 180 °C, 4 h, 30% of water, and 0.2% of catalyst, respectively, and the viscosity reduction rate was 61.74%. Under the catalysis of the isopropanol system, the viscosity reduction rate was increased to 91.22%. A series of characterizations such as freezing point, thermogravimetric analysis, DSC analysis, component analysis, gas chromatography, wax crystal morphology analysis, and GC-MS analysis of aqueous organic matter were carried out on heavy oil after reaction by different reaction systems, and it could be verified that the viscosity of heavy oil was reduced. Finally, through the study of the reaction mechanism of the model compound, combined with the aqueous phase analysis, it can be clearly found that the depolymerization between macromolecules, the breaking of heteroatom chains, hydrogenation, ring opening, and other effects mainly occur during the reaction, thereby weakening the van der Waals force and hydrogen bond of the recombinant interval, inhibiting the formation of grid structure in heavy oil and effectively reducing the viscosity of heavy oil. [ABSTRACT FROM AUTHOR]

Dehydrohalogenation of 1,4‐dihalobenzenes and 1,2,4‐trichlorobenzene is performed using n‐BuLi to form benzynes. These benzynes are used as dienophiles in a Diels–Alder reaction with the dienes furan and 2,5‐dimethylfuran to prepare new benzonorbornadiene derivatives. The cycloadducts of furan are polymerized by a ring‐opening metathesis reaction using a Hoveyda–Grubbs ruthenium catalyst. The polymers are characterized by 1H NMR (nuclear magnetic resonance), and unambiguous proton chemical shift assignments are based on the multiplicity pattern of proton resonances. This is confirmed by 2D NMR data from HSQC(Heteronuclear Single Quantum Coherence) and COSY (Correlation Spectroscopy) spectra. The polybenzonorbornadienes have both cis and trans conformation in their chemical structure. The trans conformation is qualitatively in greater proportion observed at 1H NMR experiments. These materials may have syndiotactic microstructure by the lack of correlations in COSY. [ABSTRACT FROM AUTHOR]

Numerous oil/water mixtures are produced by industrial processes and residential activities, leading to the need for effective separation technologies for wastewater treatment and environmental remediation. In the present study, we report a cellulose-based nanofiber membrane with exceptional hydrophilicity and oleophobicity that rejects organic solvents and allows the penetration of water, thus avoiding fouling by organic residues, which has been a serious issue for conventional oil/water separation membranes. The cellulose-based nanofiber membrane was fabricated through the electrospinning of cellulose acetate and subsequent deacetylation. The resulting surface hydroxyl groups were utilized to bind with the zwitterionic copolymer poly(sulfobetaine methacrylate-r-glycidyl methacrylate) via a ring-opening reaction with the epoxy groups in the copolymer. The resulting copolymer-grafted cellulose nanofiber membrane allowed the highly selective penetration of the water phase from three different oil/water mixtures. The average filtration efficiency was higher than 98% with outstanding reusability and stability over at least 20 cycles following decontamination by washing the membrane with water. The proposed material platform expands the potential use of cellulose materials to a wide range of applications in which hydrophilic coating is required. [ABSTRACT FROM AUTHOR]

The development of catalytic asymmetric reaction with water as the reactant is challenging due to the reactivity‐ and stereoselectivity‐control issues resulted from the low nucleophilicity and the small size of water. We disclose herein a chiral phosphoric acid (CPA) catalyzed atroposelective ring‐opening reaction of biaryl oxazepines with water. A series of biaryl oxazepines undergo the CPA catalyzed asymmetric hydrolysis in a highly enantioselective manner. The key for the success of this reaction is the use of a new SPINOL‐derived CPA catalyst and the high reactivity of biaryl oxazepine substrates towards water under acidic conditions. Density functional theory calculations suggest that the reaction proceeds via a dynamic kinetic resolution pathway and the CPA catalyzed addition of water to the imine group is both enantio‐ and rate‐determining. [ABSTRACT FROM AUTHOR]

Triphenylsilane (Ph3SiH) works as a Lewis‐acidic catalyst for the ring‐opening reaction of di‐ and tri‐substituted epoxides with alcohols, yielding β‐alkoxy alcohols under nearly neutral reaction conditions. This operationally simple protocol allows the facile synthesis of β‐alkoxy alcohols in good‐to‐excellent yield. [ABSTRACT FROM AUTHOR]

Copyright of Oilfield Chemistry is the property of Sichuan University, Oilfield Chemistry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Base-catalyzed ring-opening reaction of epoxides with the thiol nucleophiles is useful in the preparation and post-polymerization modification of synthetic polymers. Due to its many beneficial characteristics, this process is referred to as the thiol-epoxy 'click' reaction. In this article, our aim is to discuss the fundamental attributes of this process by tracing our own steps in the field. We initially address the aspects of efficiency, regio-selectivity, stoichiometry, and reaction conditions with the help of linear, hyperbranched, graft, dendritic, and cross-linked poly(β-hydroxy thioether)s. A special emphasis is placed on hydrogel synthesis and photopolymerization on surfaces. Subsequently, quenching of the alkoxide anion is considered which is a critical step in the formation of the β-hydroxy thioether linkage upon completion of reaction. The amenability of further reaction on the hydroxy and thioether groups through esterification and sulfur alkylation is then discussed. Initially, post-gelation/fabrication modification of sulfide linkages is considered to obtain cationic sulfonium hydrogels and zwitterionic photopatterned networks with antibacterial and antibiofouling properties, respectively. A post-synthesis functionalization strategy is then described to access same centered and segregated main-chain poly(β-hydroxy sulfonium)s as potent antibacterial materials. In side-chain polysulfides, the sequential post-synthesis modifications involving poly(glycidyl methacrylate) scaffolds can lead to the formation of amphiphilic homopolymers. The application of such materials is discussed in the arena of siRNA delivery. Finally, concerns relating to the formation of disulfide defects and open research goals such as study of the orthogonality of the reaction are addressed. [ABSTRACT FROM AUTHOR]

In situ polymerization of liquid electrolytes is currently the most feasible way for constructing solid‐state batteries, which, however, is affected by various interfering factors of reactions and so the electrochemical performance of cells. To disclose the effects from polymerization conditions, two types of generally used in situ polymerizing reactions of ring‐opening polymerization (ROP) and double bond radical polymerization (DBRP) were investigated on the aspects of monomer conversion and electrochemical properties (Li+‐conductivity and interfacial stability). The ROP generated poly‐ester and poly‐carbonate show a high monomer conversion of ≈90 %, but suffer a poor Li+‐conductivity of lower than 2×10−5 S cm−1 at room temperature (RT). Additionally, the terminal alkoxy anion derived from the ROP is not resistant to high‐voltage cathodes. While, the DBRP produced poly‐VEC(vinyl ethylene carbonate) and poly‐VC(vinylene carbonate) show lower monomer conversions of 50–80 %, delivering relatively higher Li+‐conductivities of 2×10−4 S cm−1 at RT. Compared two polymerizing reactions and four monomers, the VEC‐based F‐containing copolymer possesses advantages in Li+‐conductivity and antioxidant capacity, which also shows simultaneous stability towards Li‐metal with the help of LiF‐based passivating layer, allowing a long‐term stable cycling of high‐voltage quasi solid‐state cells. [ABSTRACT FROM AUTHOR]

[22][23] In the present case, the principle required the preparation of a set of oligomers of an easy-to-use surrogate amino acid, with transformation of all residues present into Aatc(Me) residues in the final step. Keywords: azetidines; late-stage modification; peptides; reductive amination; protected amino acid; oligomers EN azetidines late-stage modification peptides reductive amination protected amino acid oligomers 1787 1790 4 08/29/23 20230915 NES 230915 Graph In the context of a collaborative interdisciplinary program, we were recently given a particular synthetic challenge. Finally, tetramer B 9 b was deprotected as before without incident, but the resulting tetraamine tetrahydrochloride only provided small amounts (<10%) of tetramer B 4 b when subjected to the same reductive amination conditions as above. [29] While the target molecules in our work implicated Aatc(Me) as the constituent amino acid, we took the opportunity to conduct two related experiments on derivative B 6 b (Scheme 3). [Extracted from the article]

Making one out of two: Dimeric boraza‐crown ethers bridge the gap between metallacrowns and aza‐crown ethers with a strikingly simple synthesis. Dioxazaborocanes react with alkoxides to form the corresponding anionic boronates, which combine to form dimers upon ring‐opening reactions. The presence of the dimers was proven in the solid state and in solution by X‐ray crystallography and NMR spectroscopy, respectively. The influence of the sodium and potassium ions on the stability of boraza‐crown ethers was examined using DFT calculations. The dissociation of the dimers to the monomeric species was found to be endothermic, independently of the counterion. Finally, their ability to engage in cross‐coupling reactions was validated for two different compounds. [ABSTRACT FROM AUTHOR]

1,3‐Disubstituted N‐aryl‐2H‐isoindoles have been synthesized by a cascade reaction of divinyl ethers, which are derived from easily available 4‐bromoisocoumarins, with substituted anilines in HFIP. This cascade reaction consists of a ring‐opening step through addition‐elimination mechanism and the following 5‐exo‐tet type ring‐closing step via the intramolecular nucleophilic substitution reaction. Thus obtained 2H‐isoindoles have been derivatized to high‐order nitrogen‐containing polycycles including less accessible benzo[a]ullazines. [ABSTRACT FROM AUTHOR]

An excessive blood level of homocysteine (HcySH) is associated with numerous cardiovascular and neurodegenerative disease conditions. It has been suggested that direct S-homocysteinylation, of proteins by HcySH, or N-homosteinylation by homocysteine thiolactone (HTL) could play a causative role in these maladies. In contrast, ascorbic acid (AA) plays a significant role in oxidative stress prevention. AA is oxidized to dehydroascorbic acid (DHA) and if not rapidly reduced back to AA may degrade to reactive carbonyl products. In the present work, DHA is shown to react with HTL to produce a spiro bicyclic ring containing a six-membered thiazinane-carboxylic acid moiety. This reaction product is likely formed by initial imine condensation and subsequent hemiaminal product followed by HTL ring opening and intramolecular nucleophilic attack of the resulting thiol anion to form the spiro product. The reaction product was determined to have an accurate mass of 291.0414 and a molecular composition C 10 H 13 NO 7 S containing five double bond equivalents. We structurally characterized the reaction product using a combination of accurate mass tandem mass spectrometry, 1D and 2D-nuclear magnetic resonance. We also demonstrated that formation of the reaction product prevented peptide and protein N-homocysteinylation by HTL using a model peptide and α-lactalbumin. Furthermore, the reaction product is formed in Jurkat cells when exposed to HTL and DHA. [Display omitted] • Dehydroascorbate reacts with homocysteine thiolactone. • The reaction prevents protein N-homocysteinylation by homocysteine thiolactone. • The stability of the reaction product decreases at raising pH. • The reaction takes place intracellularly in Jurkat cells. [ABSTRACT FROM AUTHOR]

[8][9][10][11] Organophosphorus compounds containing epoxy groups are generally prepared by the reaction of unstable and toxic phosphorus halides with alcohols containing an epoxide group (Scheme 1a). Solvent-free reaction, alkylation, epichlorohydrocarbons, phosphonic acids, tandem reaction, epoxy phosphinates Keywords: solvent-free reaction; alkylation; epichlorohydrocarbons; phosphonic acids; tandem reaction; epoxy phosphinates EN solvent-free reaction alkylation epichlorohydrocarbons phosphonic acids tandem reaction epoxy phosphinates 1715 1718 4 08/18/23 20230901 NES 230901 Graph Owing to its high reactivity, the epoxy group is important in syntheses of pharmaceuticals and bioactive natural products. [Extracted from the article]

The aim of this study was to design and characterize a candidate molecule of biological significance by synergistically combining the unique chemical properties, biocompatibility, and low toxicity of carbon quantum dots (CNDs) by the precursor molecule o-phenylenediamine (o-PDA), which is used to produce most chemotherapeutic agents, as a CNDs/o-PDA conjugate. Using citric acid (CA), surface-functional CNDs were synthesized by simple and rapid thermal pyrolysis for 2 h at 180 °C without using chemicals. Conjugation was carried out for 16 h at 40 °C in N,N-dimethylformamide (DMF) presence of triethylamine (Et3N). Structural characterizations were performed by spectroscopic techniques such as attenuated total reflectance—Fourier transform infrared (ATR-FTIR), nuclear magnetic resonance (1H-NMR), UV–Vis, and fluorescence spectroscopy. The crystal structure of pure- and o-PDA-conjugated-CNDs was characterized using X-ray diffractometers (XRD-MF). Physical characterizations were performed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Q-TOF LC/MS (liquid chromatography–quadrupole-time-of-flight mass spectrometry) and size exclusion chromatography (SEC) were used to analyze molecular weight change and polydispersity index (PDI) as a result of o-PDA conjugation. The spherical nanoparticle size of the nanodots was confirmed by transmission electron microscopy (TEM). All results suggest that the targeted o-PDA derivatization of CNDs was successfully achieved by the ring-opening reaction. [ABSTRACT FROM AUTHOR]

The photochemical ring-opening reaction of 7-dehydrocholesterol (DHC, provitamin D3) is responsible for the light-initiated formation of vitamin D3 in mammalian skin membranes. Visible transient absorption spectroscopy was used to explore the excited state dynamics of DHC and two analogs: ergosterol (provitamin D2) and DHC acetate free in solution and confined to lipid bilayers chosen to model the biological cell membrane. In solution, the excited state dynamics of the three compounds are nearly identical. However, when confined to lipid bilayers, the heterogeneity of the lipid membrane and packing forces imposed on the molecule by the lipid alter the excited state dynamics of these compounds. When confined to lipid bilayers in liposomes formed using DPPC, two solvation environments are identified. The excited state dynamics for DHC and analogs in fluid-like regions of the liposome membrane undergo internal conversion and ring-opening on 1 ps–2 ps time scales, similar to those observed in isotropic solution. In contrast, the excited state lifetime of a subpopulation in regions of lower fluidity is 7 ps–12 ps. The long decay component is unique to these liposomes and results from the structural properties of the lipid bilayer. Additional measurements in liposomes prepared with lipids having slightly longer or shorter alkane tails support this conclusion. In the lipid environments studied, the longest lifetimes are observed for DHC. The unsaturated sterol tail of ergosterol and the acetate group of DHC acetate disrupt the packing around the molecule and permit faster internal conversion and relaxation back to the ground state. [ABSTRACT FROM AUTHOR]

We present two multistate ring polymer instanton (RPI) formulations, both obtained from an exact path integral representation of the quantum canonical partition function for multistate systems. The two RPIs differ in their treatment of the electronic degrees of freedom; while the Mean-Field (MF)-RPI averages over the electronic state contributions, the Mapping Variable (MV)-RPI employs explicit continuous Cartesian variables to represent the electronic states. We compute both RPIs for a series of model two-state systems coupled to a single nuclear mode with electronic coupling values chosen to describe dynamics in both adiabatic and nonadiabatic regimes. We show that the MF-RPIs for symmetric systems are in good agreement with the previous literature, and we show that our numerical techniques are robust for systems with non-zero driving force. The nuclear MF-RPI and the nuclear MV-RPI are similar, but the MV-RPI uniquely reports on the changes in the electronic state populations along the instanton path. In both cases, we analytically demonstrate the existence of a zero-mode, and we numerically find that these solutions are true instantons with a single unstable mode as expected for a first order saddle point. Finally, we use the MF-RPI to accurately calculate rate constants for adiabatic and nonadiabatic model systems with the coupling strength varying over three orders of magnitude. [ABSTRACT FROM AUTHOR]

The influence of ring-puckering on the light-induced ring-opening dynamics of heterocyclic compounds was studied on the sample 5-membered ring molecules γ-valerolactone and 5H-furan-2-one using time-resolved photoelectron spectroscopy and ab initio molecular dynamics simulations. In γ-valerolactone, ring-puckering is not a viable relaxation channel and the only available reaction pathway is ring-opening, which occurs within one vibrational period along the C—O bond. In 5H-furan-2-one, the C=C double bond in the ring allows for ring-puckering which slows down the ring-opening process by about 150 fs while only marginally reducing its quantum yield. This demonstrates that ring-puckering is an ultrafast process, which is directly accessible upon excitation and which spreads the excited state wave packet quickly enough to influence even the outcome of an otherwise expectedly direct ring-opening reaction. [ABSTRACT FROM AUTHOR]

Dynamics of the cycloreversion reaction of a photochromic diarylethene derivative with a small ring-opening reaction yield (∼1%) was investigated by using femtosecond transient absorption spectroscopy. The reaction rate constant and activation barrier on the reaction coordinate were quantitatively analyzed on the basis of the temperature and excitation wavelength dependencies of the reaction yield and excited state dynamics. From the comparison of the present results with those in a more reactive derivative, we concluded that a key factor regulating the overall reaction yield is the branching ratio at the conical intersection where the excited state population is split into the product and the initial reactant. The excitation wavelength dependence of the dynamics indicated that the geometrical relaxation and vibrational cooling proceed in a few picosecond time scale behind the cycloreversion process, and the vibrational excess energy assists the molecule to climb up the energy barrier. [ABSTRACT FROM AUTHOR]

The electronic properties of diphenylphthalide dicarboxylic acid (DPDA) are studied under gas-phase conditions using dissociative electron attachment spectroscopy and in the condensed environment by means of total current spectroscopy. The experimental features are assigned with the support of density functional theory calculations of the energies of the lowest-lying anion states to describe both resonances responsible for low-energy (0–15 eV) electron attachment to the isolated molecule and the maxima in the density of unoccupied electronic states in the condensed ultrathin (up to 10 nm) films. Resonance electron attachment to DPDA is found to be followed by the opening of the γ-lactone ring in the molecular negative ions, an unusual mechanism leading to their stabilization. A similar mechanism is expected to be responsible for the unique properties of phthalide-based materials in the condensed state. [ABSTRACT FROM AUTHOR]

Cyclopropanols, due to their particular chemistry, can participate in various synthetic reactions with retention or cleavage of the strained three‐membered ring. Direct cross‐coupling ring‐opening reaction of such molecules access to organic compounds, such as ketones has great importance in medicinal chemistry and material sciences. Hence, the coupling reaction/cyclization ring‐opening of cyclopropanols for constructing new valuable molecules in the presence of a transition metal catalyst or under metal‐free conditions is described in this context. The features of the reactions are discussed, and the mechanisms of the challenging reactions are highlighted. [ABSTRACT FROM AUTHOR]

Aziridine, alkyne, dihydropyrrolidine, visible light, click chemistry, photoredox catalysis As part of our continuing research interests in visible-light photoredox catalysis, [43] we have developed a novel visible-light-induced [3+2]-cycloaddition reaction of aziridines B 1 b with alkynes B 2 b (Scheme 1). Expanding aziridine chemistry further, important polysubstituted pyrrolidines can be created via atom-efficient and convergent cycloaddition reaction of aziridines with alkynes via C-C bond and C-N bond cleavage by photoredox catalysis. Keywords: aziridine; alkyne; dihydropyrrolidine; visible light; click chemistry; photoredox catalysis EN aziridine alkyne dihydropyrrolidine visible light click chemistry photoredox catalysis 1621 1625 5 07/31/23 20230815 NES 230815 Graph Using cycloaddition processes, click chemistry creates carbon-hetero atom bonds in an environmentally friendly manner. [Extracted from the article]

In this paper, the effects of HTPBs with different main-chain microstructures on their triblock copolymers and polyurethane properties were investigated. Three polyether-modified HTPB triblock copolymers were successfully synthesized via a cationic ring-opening copolymerization reaction using three HTPBs with different microstructures prepared via three different polymerization methods as the macromolecular chain transfer agents and tetrahydrofuran (THF) and propylene oxide (PO) as the copolymerization monomers. Finally, the corresponding polyurethane elastomers were prepared using the three triblock copolymers as soft segments and toluene diisocyanate (TDI) as hard segments. The results of an analysis of the triblock copolymers showed that the triblock copolymers had lower viscosity and glass transition temperature (Tg) values as the HTPB 1,2 structure content decreased, although the effect on the thermal decomposition temperature was not significant. An analysis of the polyurethane elastomers revealed that as the content of the 1,2 structure in HTPB increased, its corresponding polyurethane elastomers showed a gradual increase in breaking strength and a gradual decrease in elongation at break. In addition, PU-1 had stronger crystallization properties compared to PU-2 and PU-3. However, the differences in the microstructures of the HTPBs did not seem to have much effect on the surface properties of the polyurethane elastomers. [ABSTRACT FROM AUTHOR]

Ligand‐controlled regiodivergent cobalt‐catalyzed ring‐opening dihydroboration of arylidenecyclopropanes is developed to access synthetically versatile skipped diboronates with catalysts generated in situ from Co(acac)2 and dpephos or xantphos. A variety of arylidenecyclopropanes reacted with pinacolborane (HBpin) to form the corresponding 1,3‐ or 1,4‐diboronates in high isolated yields and with high regioselectivity. Skipped diboronate products from these reactions can undergo various transformations to allow selective installation of two different functional groups along alkyl chains. Mechanistic studies suggest that these reactions combine cobalt‐catalyzed ring‐opening hydroboration of arylidenecyclopropanes and hydroboration of homoallylic or allylic boronate intermediates. [ABSTRACT FROM AUTHOR]

In the gas phase, thermal activation of supramolecular assemblies such as host–guest complexes leads commonly to noncovalent dissociation into the individual components. Chemical reactions, for example of encapsulated guest molecules, are only found in exceptional cases. As observed by mass spectrometry, when 1‐amino‐methyl‐2,3‐diazabicyclo[2.2.2]oct‐2‐ene (DBOA) is complexed by the macrocycle β‐cyclodextrin, its protonated complex undergoes collision‐induced dissociation into its components, the conventional reaction pathway. Inside the macrocyclic cavity of cucurbit[7]uril (CB7), a competitive chemical reaction of monoprotonated DBOA takes place upon thermal activation, namely a stepwise homolytic covalent bond cleavage with the elimination of N2, while the doubly protonated CB7⋅DBOA complex undergoes an inner‐phase elimination of ethylene, a concerted, electrocyclic ring‐opening reaction. These chemical reaction pathways stand in contrast to the gas‐phase chemistry of uncomplexed monoprotonated DBOA, for which an elimination of NH3 predominates upon collision‐induced activation, as a heterolytic bond cleavage reaction. The combined results, which can be rationalized in terms of organic‐chemical reaction mechanisms and density‐function theoretical calculations, demonstrate that chemical reactions in the gas phase can be steered chemoselectively through noncovalent interactions. [ABSTRACT FROM AUTHOR]

Novel sulfonated phenylamine ionic liquids were prepared through a simple ring-opening reaction of phenylamine with 1,3-propanesulfonate (PS) and evaluated as catalysts for the esterification of trimethylolpropane and acrylic acid to produce trimethylolpropane acrylate. By adjusting the molar ratio of PS to phenylamine, sulfonated phenylamine (PSn-PA) with different PS group numbers (n = 1, 2, 3) can be obtained. Among them, PS3-PA possessed the strongest acidity and presented the best trimethylolpropane conversion (100%) and TMPTA selectivity (85.4%) under mild reaction conditions. The results showed that the catalytic performances of PSn-PA were closely related to their acidic strength. A possible mechanism for the enhanced catalytic activity in the presence of these novel sulfonated phenylamine ILs had been proposed. Moreover, an obvious phase-separation phenomenon, in which the catalyst completely dissolved in a reaction system, but precipitated at the end of reaction, was observed during the reaction process. This work provided an efficient and simple approach for the design of new ionic liquids with multiple acidic sites. This kind of acidic catalyst with phase separation behavior and high performance has potential to be used in more acid-catalyzed reactions, especially for polycarboxylic acid or polyol systems. [ABSTRACT FROM AUTHOR]

The need for sustainable and environment-friendly materials has led to growing interest in the development of biodegradable polymers based on natural compounds. However, metal-based catalysts used in the polymerization process may cause concerns about the toxicity of the resultant polymers. Therefore, polymers derived from natural compounds and synthesized through the use of green catalysts are highly desirable. Lipase-catalyzed ring-opening polymerization (ROP) of biocompound-based cyclic monomers has emerged as a promising and green strategy for the design and synthesis of such polymers. In this review, we summarize reports on the use of ROP catalyzed by lipase for cyclic monomers derived from natural compounds, including bile acid- and porphyrin-based macrocycles, carbonate-based macrocycles, lactones, and cyclic anhydrides, with an emphasis on ring-closure reactions for the synthesis of cyclic monomers, the types of lipases for the ROP and the choice of reaction conditions (temperature, solvent, reaction time, etc.). Moreover, the current challenges and perspectives for the choice and reusability of lipases, ring-closure versus ring-opening reactions, monomer design, and potential applications are discussed. [ABSTRACT FROM AUTHOR]

Among biobased and biodegradable polymers, polylactic acid (PLA) is most widely used one. However, its poor mechanical properties need to be enhanced. In this study, PLA blend film with improved mechanical properties were developed without compromising any bio-content. For this, natural rubber derivative with acetate pendant group (ANR) and PLA blend films were prepared. First, natural rubber was epoxidized, and then partial acetylation was achieved by the ring-opening reaction of the epoxy groups. The epoxidation and the acetylation were examined by FTIR analysis. 1H-NMR spectrum revealed a 29% epoxidation and 8.25% acetylation degree. The Tg of natural rubber (−66°C) increased to −41°C and −31°C after epoxidation and acetylation, respectively. The compatibility of ENR and ANR with PLA was evident from the DSC results and Molau test. The morphology of PLA blend film containing 25 wt% of ANR (ANR25) was observed as well-dispersed fine droplets by SEM images. The tensile strength, elastic modulus, and yield strength of ANR25 were measured as 11.6 MPa, 397.3 MPa, and 6.9 MPa, respectively. These values are considerably higher than neat PLA film. Compared to reported studies on PLA toughening so far, increments in both the strength and elongation of ANR25 were observed by tensile tests. Moreover, highest toughness among all samples was determined as 18.8 MJm−3 for ANR25, which is 1.8 times higher than neat PLA. Thus, a strong and tough bio-based PLA blend was developed for film application such as packaging and sheeting. [ABSTRACT FROM AUTHOR]

The ring-opening reactions of 1,2-epoxides are important topics in organic chemistry courses. The description of the ring-opening reaction of epoxides in textbooks lacks quantitative and visual information; therefore, students usually learn it by rote and cannot fully understand the mechanisms involved. This experiment presents a prototypical example of investigating the molecular mechanism of a chemical reaction using theoretical chemistry methods. By carrying out quantum chemical calculations on the ring-opening reactions of a typical 1,2-epoxide catalyzed by an acid or base, we reveal the thermodynamic and kinetic properties of the reaction and provide an intuitive physical picture and quantitative information of the reaction for understanding the regioselectivity of the reaction. This experiment will not only help students deepen their understanding of the basic concepts and theories of chemistry but also help them broaden their horizons and expand their thinking, making them realize that theoretical calculation is an important tool in chemical research. [ABSTRACT FROM AUTHOR]

[35] Acetylation of 11 to 12; General Procedure C To a solution of B 11 b (20.0 mmol) in DCM (120 mL) were added Et SB 3 sb N (13.9 mL, 100 mmol) and Ac SB 2 sb O (9.45 mL, 100 mmol). Keywords: pyrone; furfural; furfuryl alcohol; renewable resources; Piancatelli- rearrangement; flash vacuum pyrolysis EN pyrone furfural furfuryl alcohol renewable resources Piancatelli- rearrangement flash vacuum pyrolysis 2304 2310 7 07/14/23 20230801 NES 230801 Graph The production pathways in the chemical industry are mainly based on non-renewable resources like natural gas, oil, and coal. Herein we report the atom economic conversion of furfural via furfuryl alcohol ( B 4 b ) into 2-pyrone ( B 1 b ) on a multigram scale and, in extension, to naturally occurring 6-substituted pyrone derivatives. Extending the synthetic strategy towards substituted pyrones, furfuryl alcohol derivatives B 10 b were readily obtained by adding Grignard reagents to furfural ( B 9 b ). [Extracted from the article]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Although the benefits of mechanochemistry for solid-state reactions of compounds with reactive bonds, such as organic halides, have been well demonstrated, nonactivated bond cleavage through mechanochemical transformation remains unexplored. Keywords: C-C bond cleavage; fluorination; mechanochemistry; ball-milling; solid-state chemistry; silver catalysis EN C-C bond cleavage fluorination mechanochemistry ball-milling solid-state chemistry silver catalysis 1419 1424 6 07/11/23 20230725 NES 230725 Graph In recent years, solvent-free solid-state organic transformations using ball-milling, known as mechanochemical reactions, have been extensively studied as new tools for organic chemistry. C-C bond cleavage, fluorination, mechanochemistry, ball-milling, silver catalysis, solid-state chemistry. [Extracted from the article]

Keywords: Rh(II) catalysis; N -tosylhydrazone; 1,2-shift; metal carbene; cyclobutene; cyclopropane EN Rh(II) catalysis N -tosylhydrazone 1,2-shift metal carbene cyclobutene cyclopropane 1507 1511 5 07/11/23 20230725 NES 230725 Graph The cyclobutenes represents a unique type of structures in organic chemistry and have attracted considerable attentions in the past decades. In addition, considering the large ring tension of cyclobutene, we studied the olefin metathesis reaction of cyclobutene B 2a b with styrene. Chem. 2009, 1: 537 54 All the reactions of rhodium-catalyzed ring expansion of cyclopropanes to cyclobutenes were performed under nitrogen atmosphere in a flame-dried reaction tube. [Extracted from the article]

The efficient one-pot halofluorination of a β-enaminophosphonate/β-iminophosphonate tautomeric mixture resulting in α,α-halofluorinated β-iminophosphonates is reported. Subsequent imine reduction gave the corresponding β-aminophosphonates as a racemic mixture or with high diastereoselectivity. The proposed protocol is the first example of a synthesis of N-inactivated aziridines substituted by a fluorine and phosphonate moiety on the same carbon atom. Based on spectroscopic and theoretical studies, we determined the cis/trans geometry of the resulting fluorinated aziridine-2-phosphonate. Our procedure, involving the reduction of cis/trans-fluoroaziridine mixture 24, allows us to isolate chiral trans-aziridines 24 as well as cis-aziridines 27 that do not contain a fluorine atom. We also investigated the influence of the fluorine atom on the reactivity of aziridine through an acid-catalyzed regioselective ring-opening reaction. The results of DFT calculations, at the PCM/ωB97x-D/def2-TZVPD level of theory, are in good agreement with the experiments. The transition states of the SN2 intramolecular cyclization of vicinal haloamines have been modeled. [ABSTRACT FROM AUTHOR]

Developing a new strategy to improve the self‐assembly efficiency of functional assemblies in a confined space and construct hybrid functional materials is a significant and fascinating endeavor. Herein, we present a highly efficient strategy for achieving the supramolecular self‐assembly of well‐defined metallacages in microdroplets through continuous‐flow microfluidic devices. The high efficiency and versatility of this approach are demonstrated by the generation of five representative metallacages in different solvents containing water, DMF, acetonitrile, and methanol in a few minutes with nearly quantitative yields, in contrast to the yields obtained with the hour‐scale reaction time in a batch reactor. A ring‐opening catalytic reaction of the metallacages was selected as a model reaction for exploring supramolecular catalysis in microdroplets, whereby the catalytic yield was enhanced by 2.22‐fold compared to that of the same reaction in the batch reactor. This work illustrates a new promising approach for the self‐assembly of supramolecular systems. [ABSTRACT FROM AUTHOR]

Fluorescent carbon quantum dots (CQDs), specified by feature sizes of <10 nm, have become a mystic newcomers in the world of nanoscience and attracted much focus of synthetic chemists since the last decade due to their esoteric physico-chemical features. Because of these magical characteristics, carbon dots-based catalytic systems have unlocked the gateway for eco-friendly, benign, and cost-effective next-generation platform for "Nanocatalysis and Photocatalysis" in organic synthesis. The introduction of CQDs in organic synthesis allows the designing new reactions or catalysis in which unique/unprecedented connection/disconnection of chemical bonds has been implemented for the construction of new molecular architectures. This critical review presents a comprehensive study of the catalytic and photocatalytic efficiency of CQDs in organic synthesis which has initiated a more sustainable strategy in to the catalysis field. By systematic summarization and categorization of various organic transformations such as coupling reactions, oxidation reactions, reduction reactions, condensation reactions, ring-opening reactions, epoxidation, C-H activation, etc., a clear picture of all available catalytic and photocatalytic strategies for CQDs are presented and their unique role in various catalytic approaches for specific reactions are discussed in detail. Catalytic aspects of CQDs in heterocyclic synthesis are also been reviewed. Finally, challenges and future aspects associated with the green catalytic efficiency of CQDs in organic synthesis are highlighted. Herein, this review summarizes the current investigations on CQDs for various organic transformations during last 10 years. We experience that the entire potential of CQDs in organic synthesis has yet to be fully explored in organic synthesis. We hope that this review is serving as a humble urge to encourage other organic chemists for further use of CQDs as a sustainable catalyst in organic synthesis. [ABSTRACT FROM AUTHOR]

Purpose: The study aims to investigate the anticorrosion performance of epoxy coatings using modified cerium oxide (CeO2) by terephthalic acid (CeO2-t) and fumaric acid (CeO2-f) as corrosion inhibitors. Design/methodology/approach: The chemical state of CeO2-t, and CeO2-f were analyzed by infrared radiation (IR) and X-ray diffraction (XRD). The effect of different inhibitors on the coating properties was analyzed by neutral salt spray tests (NSST) and electrochemical impedance spectroscopy (EIS). Findings: The results of IR and XRD illustrate that the modification of CeO2 was successful, and fumaric acid underwent a ring-opening reaction with epoxy resin (EP) in the coatings. The results of NSST and EIS showed that the coatings containing CeO2-f exhibited the best anticorrosion performance. Originality/value: CeO2 is an effective inhibitor of the organic coatings. When surface modified, it is chemically bonded to EP, enhancing the anticorrosion performance of EP. [ABSTRACT FROM AUTHOR]

Three kinds of Pt nanocrystals with different morphologies (5 nm cubes, 10 nm cubes and 5 nm truncated octahedrons) were synthesized and employed to fabricate Pt/CNT-USY catalysts for selective ring opening of decalin. The 5 nm truncated octahedral Pt/CNT-USY with exposed (100) and (111) facets exhibited higher yield of ring-opening products (53.9 wt%) than the CNT-USY-supported 5 nm cubic Pt catalyst enclosed by the (100) facets (39.6 wt%). Moreover, the 5 nm cubic Pt showed better catalytic activities compared to the 10 nm cubic Pt/CNT-UST catalyst, which ascribed to the smaller size of Pt NCs enriched more revealable metal active sites. DFT calculations demonstrated that the adsorption of decalin on Pt (111) was stronger than that on Pt (100) facets, which was profitable for the selective ring-opening reaction. [ABSTRACT FROM AUTHOR]

As one of the most toxic metals, Mercury ions cause serious environmental pollution and threaten the health of living organisms. Hence, we designed and synthesised a new near-infrared (NIR) ratiometric fluorescent probe toward monitoring of Hg2+ based on quinoline-fused rhodamine dye. Owing to the specific spirolactam ring-opening reaction, the probe exhibits a ratiometric fluorescent change after treatment of Hg2+ with increased emission in NIR and significantly reduced emission in visible region. The specific response mechanism and dual-channel fluorescence change allow the probe to have remarkable detection selectivity, fast response and high detection sensitivity. Moreover, with the properties of excellent cell permeability and low cytotoxicity, probe can be applied as detection tool for mercury ions with dual-channel ratiometric fluorescence imaging in living cell. [ABSTRACT FROM AUTHOR]

Rigid polyurethane foam (RPUF) is prepared from petroleum‐based polyols and isocyanate, which consumes a large amount of petroleum. To alleviate the consumption of petroleum, it is necessary to synthesize green and sustainable polyols. However, the greatest disadvantage of RPUF is its flammability. To reduce the risk of fire caused by RPUF, phosphorylated soybean oil polyol (Polyol‐P) and phenyl phospho‐soybean oil polyol (Polyol‐PPOA) were synthesized by ring‐opening reactions of epoxy soybean oil with phosphoric acid and phenylphosphonic acid, respectively. A flame‐retardant RPUF was prepared via polymeric 4,4‐diphenylmethane diisocyanate (p‐MDI), which reacted after mixing Polyol‐P and Polyol‐PPOA with polyether polyol‐330N in different proportions. Scanning electron microscopy (SEM) showed that the cell sizes of the RPUF‐P and RPUF‐PPOA increased first and then decreased and the cell number decreased first and then increased with the increase in the contents of Polyol‐P and Polyol‐PPOA. Mechanical property tests showed that the compressive strength of the RPUF‐P4 reached 0.1 MPa, and the compressive strength of the RPUF‐PPOA4 reached 0.07 MPa. The limiting oxygen index values of the RPUF‐P4 and RPUF‐PPOA4 were 20.9% and 24.3%, respectively. The UL 94 of the RPUFs indicated that the rating of the RPUF‐PPOA3 was improved to V‐1. The results showed that the flame‐retardancy mechanism of the Polyol‐P and Polyol‐PPOA in the RPUF was based on the charred surface as a physical barrier, which slowed down the decomposition of RPUF and prevented heat and mass transfer between the gas and the condensed phase. [ABSTRACT FROM AUTHOR]

As a novel energetic material, 5‐Amino‐1H‐tetrazole (5AT) has a history of proposed applications in the fields of airbags, rocket engines, and new propellants. However, the application of 5AT is limited for its poor combustion stability. Identification of the thermal behaviour and pyrolysis mechanism of 5AT could provide guidance on the control of combustion behaviour, which can be effectively improved by adding oxidizers. In this paper, five kinds of oxidizers (Ammonium perchlorate (AP), Sodium perchlorate (NaClO4), Ammonium nitrate (AN), Manganese oxide (MnO2), and Chromic oxide (Cr2O3)) are mixed with 5AT for investigating the catalytic effects of multi‐type oxidizers on 5AT. Thermal behaviour is analysed by the TG‐DSC test and the thermal activation energy is evaluated by Kissinger and Ozawa methods. Moreover, TG‐FTIR and TG‐MS analyses are used to infer the pyrolysis gas products of 5AT/oxidant. The experimental results indicate that the 5AT‐AN has the lowest activation energy, and the degradation process was simplified into one step. The addition of AP, NaClO4, and MnO2 can promote the pyrolysis process of 5AT due to the redox reaction between melamine and the decomposition products of oxidizers, while the catalytic effect of Cr2O3 mainly occurs above 400 °C without the occurrence of oxidation. The catalytic mechanism of Cr2O3 mainly performs on the polyaddition and the ring‐opening reaction of N‐containing heterocycles. The findings of this work may offer valuable direction for understanding, designing, and using 5AT‐based propellants. [ABSTRACT FROM AUTHOR]

Effective pollutant removal with environmentally friendly materials has attracted considerable attention. Herein, macroporous polyHIPE-g-poly(glycidyl methacrylate)-β-cyclodextrin (a) was prepared via a combination of high-internal-phase emulsion (HIPE) polymerization, atom-transfer radical polymerization (ATRP), and ring-opening addition reaction techniques. Based on the PGMA brush, β-CD molecules were successfully grafted onto the surface of PHIPE. Characterization of the obtained material demonstrated a hierarchical porous structure and the successful grafting of β-CD. Attributed to the large surface area of the monolith and the host–guest molecular recognition between β-CD and BPA, the prepared PHIPE-g-PGMA-β-CD as a robust macroporous complex could effectively remove BPA from water. The removal efficiency was systematically investigated with varying the time and concentration. Moreover, the monolith could be reused by simply leaching and washing in methanol to elute BPA, displaying comparative regeneration efficiency after six cycles. The newly fabricated macroporous PHIPE-g-PGMA-β-CD has great potential application in BPA-contaminated water treatment and environmental protection. [ABSTRACT FROM AUTHOR]

Transition metal‐catalyzed hydrofunctionalization of methylenecyclopropanes (MCPs) has presented a considerable challenge due to the difficult manipulation of regioselectivity and complicated reaction patterns. Herein, we report a straightforward Pd‐catalyzed ring‐opening hydrophosphinylation reaction of MCPs via highly selective C−C bond cleavage. This method allows for rapid and efficient access to a wide range of chiral allylic phosphine oxides in good yields and high enantioselectivities. Additionally, density functional theory (DFT) calculations were performed to elucidate the reaction mechanism and the origin of enantioselectivity. [ABSTRACT FROM AUTHOR]

A composite with shape memory‐assisted self‐healing and piezoresistive sensing ability is presented herein, and its high conductivity is attributed to a small amount of well‐dispersed carbon black (CB). Carboxylic acid groups are introduced into the polyvinyl butyral (PVB) side chain via the ring‐opening reaction of succinic anhydride. Thus, CB is well‐dispersed in the solution owing to simultaneous attraction and electrostatic repulsion. The resulting ink with less than 30 wt.% CB is highly conductive (3.7 S cm−1). In addition, hexamethylene diisocyanate (HDI) is used as a crosslinking agent to promote the reaction between OH and COOH in the side chains of the PVB‐COOH. The dual network consisting of urethane and amide bonds exhibits the shape memory effect. Moreover, the composite is shown to be capable of shape memory‐assisted self‐healing owing to the hydrogen bonds between the dual network and COOH, such that the resistance returns to its initial value, and the healed sample can support a 1 kg weight. The resulting multi‐modal sensing system is shown to detect bio‐signals such as body movements, breathing, and pulse. In summary, the present work provides an effective strategy for the development of conductive composite electrodes for various applications that require adaptability and piezoresistive sensing ability. [ABSTRACT FROM AUTHOR]

The synthesis of chiral contiguous cyclopropylaziridine was achieved through cyclopropanation of (E)‐3‐((S)‐1‐[(R)‐1‐phenylethyl)aziridin‐2‐yl]acrylaldehyde with bromomalonate in the presence of (2R)‐ or (2S)‐[diphenyl(trimethylsilyloxy) methyl]pyrrolidine as a chiral organocatalyst and 2,6‐lutidine as a base. This chiral cyclopropylaziridine was then subjected to various functional transformations, leading to the construction of a wide range of structurally important motifs. [ABSTRACT FROM AUTHOR]

Aziridines are highly valued synthetic targets in organic and medicinal chemistry. The organocatalytic synthesis of such structures with broad substrate scope and good diastereoselectivity, however, is rare. Herein, we report a broadly applicable and diastereoselective synthetic method for the synthesis of trans‐aziridines from imines and benzylic or alkyl halides utilizing sulfenate anions (PhSO–) as the catalyst. Substrates bearing heterocyclic aromatic groups, alkyl, and electron‐rich and electron‐poor aryl groups were shown to be compatible with this method (33 examples), giving good yields and high diastereoselectivities (trans : cis >20 : 1). Further functionalization of aziridines containing cyclopropyl or cyclobutyl groups was achieved through ring‐opening reactions, with a cyclobutyl‐substituted norephedrine derivative obtained through a four‐step synthesis. We offer a mechanistic proposal involving reversible addition of the deprotonated benzyl sulfoxide to the imine to explain the high trans‐diastereoselectivity. [ABSTRACT FROM AUTHOR]

Nitrogen-rich porous organic polymers were fabricated through a nonreversible ring-opening reaction from polyamines and polyepoxides (PAEs). The epoxide groups reacted with both primary and secondary amines provided by the polyamines at different epoxide/amine ratios with polyethylene glycol as the solvent to form the porous materials. Fourier-transform infrared spectroscopy confirmed the occurrence of ring opening between the polyamines and polyepoxides. The porous structure of the materials was confirmed through N2 adsorption–desorption data and scanning electron microscopy images. The polymers were found to possess both crystalline and noncrystalline structures, as evidenced by X-ray diffraction and high-resolution transmission electron microscopy (HR-TEM) results. The HR-TEM images revealed a thin, sheet-like layered structure with ordered orientations, and the lattice fringe spacing measured from these images was consistent with the interlayer of the PAEs. Additionally, the selected area electron diffraction pattern indicated that the PAEs contained a hexagonal crystal structure. The Pd catalyst was fabricated in situ onto the PAEs support by the NaBH₄ reduction of the Au precursor, and the size of the nano-Pd was about 6.9 nm. The high nitrogen content of the polymer backbone combined with Pd noble nanometals resulted in excellent catalytic performance in the reduction of 4-nitrophenol to 4-aminophenol. [ABSTRACT FROM AUTHOR]

The figure a shown the schematic diagram of the pre-crosslinking rod-coating technique. First, GO and PPD underwent a crosslinking reaction for 180 min at 60℃ using DMF as the solvent to generate amide bonds, resulting in the formation of a pre-crosslinked GO-PPD solution (2 mg/ml). The main reaction involved the epoxy ring-opening reaction between the amine in PPD and the epoxy group in GO, resulting in a hydroxyl group and secondary amine. [Display omitted] • A large-area GO NF membrane was prepared by Pre-Crosslinking Rod Coating Technique. • The obtained GO-PPD NF membrane showed superior 99% rejection rate for dyes. • The permeability of GO-PPD NF membrane was 10 times that of non-crosslinking GO NF membrane. In existing separation membranes, it is difficult to quickly produce large-area graphene oxide (GO) nanofiltration membranes with high permeability and high rejection, which is the bottleneck of industrialization. In this study, a pre-crosslinking rod-coating technique is reported. A GO-P-Phenylenediamine (PPD) suspension was obtained by chemically crosslinking GO and PPD for 180 min. After scraping and coating with a Mayer rod, the ultra-thin GO-PPD nanofiltration membrane with an area of 400 cm2 and a thickness of 40 nm was prepared in 30 s. The PPD formed an amide bond with GO to improve its stability. It also increased the layer spacing of GO membrane, which could improve the permeability. The prepared GO nanofiltration membrane had a 99 % rejection rate for dyes such as methylene blue, crystal violet, and Congo red. Meanwhile, the permeation flux reached to 42 LMH/bar, which was 10 times that of the GO membrane without PPD crosslinking, and it still maintained excellent stability under strongly acidic and basic conditions. This work successfully solved the problems of GO nanofiltration membranes, including the large-area fabrication, high permeability and high rejection. [ABSTRACT FROM AUTHOR]

Tri‐ and tetra‐substituted alkenes, including fluoroalkenes, were prepared by a selective ring‐opening reaction of functionalized oxetanes. The introduction of adenine nucleic base allows the synthesis of alkenyl and fluoroalkenyl derivatives that were evaluated towards DltA enzyme as potential nucleoside mimics. [ABSTRACT FROM AUTHOR]

Stimuli-responsive controlled drug delivery systems have attracted the attention of researchers in recent decades due to their potential application in developing efficient drug carriers that are responsive to applied stimuli triggers. In this work, we present the synthesis of L-lysine (an amino acid that combines both amine and carboxylic acid groups in a single unit) modified mesoporous silica nanoparticles (MS@Lys NPs) for the delivery of the anticancer bioactive agent (curcumin, Cur) to cancer cells. To begin, mesoporous silica hybrid nanoparticles (MS@GPTS NPs) with 3-glycidoxypropyl trimethoxy silane (GPTS) were synthesized. The L-lysine groups were then functionalized onto the mesopore channel surfaces of the MS@GPTS NPs through a ring-opening reaction between the epoxy groups of the GPTS and the amine groups of the L-lysine units. Several instrumental techniques were used to examine the structural properties of the prepared L-lysine-modified mesoporous silica nanoparticles (MS@Lys NPs). The drug loading and pH-responsive drug delivery behavior of MS@Lys NPs were studied at different pH levels (pH 7.4, 6.5, and 4.0) using curcumin (Cur) as a model anticancer bioactive agent. The MS@Lys NPs' in vitro cytocompatibility and cell uptake behavior were also examined using MDA-MB-231 cells. The experimental results imply that MS@Lys NPs might be used in cancer therapy as pH-responsive drug delivery applications. [ABSTRACT FROM AUTHOR]