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DIAMINES, MOLECULAR docking, CYTOCHROME c, SCHIFF bases, PEROXIDASE, ESCHERICHIA coli, and DENSITY functional theory

• Synthesis of symmetrical bis-benzoxazines. • Density Functional Theory (DFT) estimation was disclosed for compound 5e. • A Molecular docking study was carried out against Cytochrome c Peroxidase (2 × 08). • Compounds 3 g, 4 g, 5c, and 5 g showed remarkable antimicrobial activity. • Compounds 3b, 3c, 3 g, 4c, 5b, & 5f displayed good antioxidant activity. We herein report the efficient synthesis of symmetrical bis-benzoxazines by substituted salicylaldehydes and alkyl diamines. The substituted salicylaldehydes (1a-d) and alkyl diamines (2a-b) on reaction synthesize Schiff's bases 3a-h. These compounds on reduction with NaBH4 in dry methanol yielded 2,2′-((alkyl-1,2-diylbis (azanediyl)) bis(methylene))disubstituted phenol, 4a-h in good yield. The preferable 1,2-bis(6-substituted-2 H -benzo[ e ][1,3]oxazin-3(4 H)-yl)ethanes, 5a-h formed when the compounds 4a-h undergo an internal Mannich reaction with formaldehyde. Different spectroscopic methods prove the formation of all the compounds. The compounds 3 g, 4 g, 5c, and 5 g showed excellent antibacterial activity against S. aureus, E. coli, S. Typhi, and B. subtilis , antifungal activity against A. flavus, C. Albicans, A. niger, and C. oxysporum with MIC values of 6.25 µg/ml and anti-TB activity against M. tuberculosis for which is equivalent to the standard drug. Furthermore, studies on the antioxidant activity of the compounds 3b, 3c, 3 g, 4c, 5b, and 5f revealed that they have excellent antioxidant activity. To comprehend the electronic behavior of compound 5e, Density Functional Theory estimations at the DFT/B3LYP level via 6–31G++ (d, p) replicate the structure and geometry. The first-order hyperpolarizability calculation finds the non-linear visual feature of compound 5e. Finally, HOMO and LUMO analysis were used for the charge transfer interface between the structures. Against Cytochrome c Peroxidase (2 × 08), the compounds 3c and 4c exhibited good docking properties in Molecular docking studies. [Display omitted] [ABSTRACT FROM AUTHOR]

AMINO acids, COLLOIDAL gels, CATALYST supports, LIGHT beating spectroscopy, and TRANSMISSION electron microscopy

Polyacrylamide-based waterborne microgels were prepared with copolymerized carboxylic acid and tertiary amine moieties. The colloidal gels were loaded with palladium nanoparticles and utilized for the Suzuki–Miyaura cross-coupling of amino acids and peptides. The thermoresponsive properties of the prepared microgels were characterized by means of photon correlation spectroscopy (PCS) at solvent conditions of the catalytic reaction. The localization and morphology of the incorporated nanoparticles were characterized with transmission electron microscopy (TEM). Palladium-catalyzed Suzuki–Miyaura cross-coupling of N α-Boc-4-iodophenylalanine and N α-Boc-7-bromotryptophan with phenylboronic acid was carried out under ambient atmosphere in water at 20, 37, and 60 °C, respectively. The properties of the thermoresponsive microgel showed a strong influence on the reactivity and selectivity towards the respective substrate. For the amine containing microgels, a recyclability for up to four cycles without loss in activity could be realized. Furthermore, the systems showed good catalytic activity regarding Suzuki–Miyaura cross-coupling of halogenated amino acids in selected tri- and tetrapeptides. [ABSTRACT FROM AUTHOR]

IODINE, CHEMICAL synthesis, HYDRAZONES, POTASSIUM carbonate, HETEROCYCLIC compounds, OXIDATION, and HYDRAZONE derivatives

An oxidative cyclization of 2‐arenoxybenzaldehyde N‐acyl hydrazones 3 a–o was employed to synthesize new 2,5‐disubstituted 1,3,4‐oxadiazole compounds 4 a–d, 4 f–i, 4 k–n. This method involves oxidative cyclization of 2‐arenoxybenzaldehyde N‐acyl hydrazones 3 a–o with molecular iodine mediated catalysis in which potassium carbonate served as a base. Characterization of all the synthesized novel compounds involved, proton and carbon NMR, mass spectrometry, and CHN elemental analysis. The synthesis of novel 2,5‐disubstituted 1,3,4‐oxadiazoles may display potential to provide pharmacologically important heterocyclic compounds. [ABSTRACT FROM AUTHOR]

CHEMICAL processes, ORGANIC acids, AMIDES, ENANTIOMERIC purity, ENZYMES, AMIDATION, ACYL chlorides, and ORGANIC solvents

Efficient amide formation is of high importance for the chemical and pharmaceutical industry. The direct biocatalytic one-pot transformation of acids into amides without substrate activation is a highly desirable but highly challenging reaction; this is why in general the acid is activated using additional reagents before amide formation occurs. In particular, amidation of α-amino acids is challenging and in general requires protection strategies for the amino functionality. A further challenge is the low solubility of the unprotected amino acids in organic solvents. Furthermore, the amidation process is prone to racemisation as observed for the acyl chloride derivative. These three challenges may be addressed using biocatalysis. Here the enzyme catalyzed, racemization-free amidation of unprotected L-proline with ammonia in an organic solvent is described. Comprehensive reaction, solvent and enzyme engineering allowed obtaining high L-prolinamide concentrations. For instance at 145 mM substrate concentration, 80% conversion was achieved employing an immobilized CalB variant and ammonia in 2-methyl-2-butanol at 70 °C. A twofold increase in L-prolinamide formation was achieved employing the immobilized and engineered enzyme variant CalBopt-24 T245S compared to wild type CalB. In contrast to chemical processes, racemization, halogenated solvents and waste are avoided/minimized and atom efficiency is significantly improved from 45.5% to 86.4%. The excellent optical purity of the obtained product (ee >99%) and the stability of immobilized CalB pave the way for an innovative industrial process to produce L-prolinamide, a key intermediate in drug synthesis. [ABSTRACT FROM AUTHOR]

TITANIUM catalysts, ALLYL alcohol, HYDROGEN peroxide, EPOXIDATION, ALCOHOL oxidation, ALCOHOL drinking, and TETRAHYDROFURAN

In the Sharpless asymmetric epoxidation of chiral secondary allylic alcohols, one substrate enantiomer is predominantly converted to the anti‐epoxy alcohol. We herein report the first highly syn‐selective epoxidation of terminal allylic alcohols using a titanium salalen complex as catalyst, at room temperature, and aqueous hydrogen peroxide as oxidant. With enantiopure terminal allylic alcohols as substrates, the epoxy alcohols were obtained with up to 98 % yield and up to >99 : 1 dr (syn). Catalyst loadings as low as 1 mol % can be applied without eroding the syn‐diastereoselectivity. Modification of the allylic alcohol to an ether does not affect the diastereoselectivity either [>99 : 1 dr (syn)]. Inverting the catalyst configuration leads to the anti‐product, albeit at lower dr (ca. 20 : 1). The synthetic potential is demonstrated by a short, gram‐scale preparation of a tetrahydrofuran building block with three stereocenters, involving two titanium salalen catalyzed epoxidation steps. [ABSTRACT FROM AUTHOR]

ORGANIC synthesis, ALKYNES, HYDROXYLATION, ALUMINUM oxide, and SUPERHEAVY elements

The discovery and development of new synthetic methods exploiting earth-abundant-element-based catalysts is an important goal in contemporary synthetic organic chemistry, which faces increasingly stringent requirements of sustainability. In this work, we disclose alumina-mediated propargylic C–H activation inducing a challenging transformation of readily available alkynes into a valuable 1,3-diene moiety under unprecedentedly mild conditions. Combining DFT-investigation and synthetic observations, we demonstrate that partial hydroxylation of alumina's surface might play an essential role in this process. [ABSTRACT FROM AUTHOR]

SOLAR cells, PYRENE, SURFACE interactions, THIOPHENES, and SELENOPHENE

A new class of polymeric hole‐transport materials (HTMs) are explored by inserting a two‐dimensionally conjugated fluoro‐substituted pyrene into thiophene and selenophene polymeric chains. The broad conjugated plane of pyrene and "Lewis soft" selenium atoms not only enhance the π–π stacking of HTM molecules greatly but also render a strong interaction with the perovskite surface, leading to an efficient charge transport/transfer in both the HTM layer and the perovskite/HTM interface. Note that fluorine substitution adjacent to pyrene boosts the stacking of HTMs towards a more favorable face‐on orientation, further facilitating the efficient charge transport. As a result, perovskite solar cells (PSCs) employing PE10 as dopant‐free HTM afford an excellent efficiency of 22.3 % and the dramatically enhanced device longevity, qualifying it among the best PSCs based on dopant‐free HTMs. [ABSTRACT FROM AUTHOR]

METALS, CYCLOPROPANE, DIOLEFINS, MOIETIES (Chemistry), INDUSTRIAL applications, and ALLYLIC amination

Biologically potent and synthetically significant 1,2‐dihydronaphthalene derivatives have gained considerable attention due to their wide applications in industrial as well as in medicinal fields also. A mild and efficient metal‐free protocol via the rearrangement of cyclopropylcarbinols has been reported to construct these 1,2‐dihydronaphthalene skeletons utilizing cyclopropane ring as the scaffold. We obtained conjugated dienes and, in some cases, homoallylic chlorides as major products in good to excellent yields. They have no literature precedence till date. The fate of this rearrangement depends on the substituent patterns of the cyclopropane bearing aryl moiety. Besides the synthetic studies, to get deep insight into the electronic transitions, time dependent DFT studies have also been performed. [ABSTRACT FROM AUTHOR]

AUTOCATALYSIS, KINETIC isotope effects, ALDEHYDES, and ZWITTERIONS

Under aprotic conditions, the stoichiometric reaction of N‐heterocyclic carbenes (NHCs) such as imidazolidin‐2‐ylidenes with aldehydes affords Breslow Intermediates (BIs), involving a formal 1,2‐C‐to‐O proton shift. We herein report kinetic studies (NMR), complemented by DFT calculations, on the mechanism of this kinetically disfavored H‐translocation. Variable time normalization analysis (VTNA) revealed that the kinetic orders of the reactants vary for different NHC‐to‐aldehyde ratios, indicating different and ratio‐dependent mechanistic regimes. We propose that for high NHC‐to‐aldehyde ratios, the H‐shift takes place in the primary, zwitterionic NHC‐aldehyde adduct. With excess aldehyde, the zwitterion is in equilibrium with a hemiacetal, in which the H‐shift occurs. In both regimes, the critical H‐shift is auto‐catalyzed by the BI. Kinetic isotope effects observed for R‐CDO are in line with our proposal. Furthermore, we detected an H‐bonded complex of the BI with excess NHC (NMR). [ABSTRACT FROM AUTHOR]

ALDEHYDES

Keywords: Autocatalysis; Breslow Intermediate; Carbenes; NMR; Reaction Mechanisms EN Autocatalysis Breslow Intermediate Carbenes NMR Reaction Mechanisms 1 1 1 06/01/22 20220607 NES 220607 B Breslow intermediates b (BIs) are pivotal species in Umpolung catalysis effected by N-heterocyclic carbenes (NHCs). Inside Back Cover: Formation of Breslow Intermediates from N-Heterocyclic Carbenes and Aldehydes Involves Autocatalysis by the Breslow Intermediate, and a Hemiacetal (Angew. Autocatalysis, Breslow Intermediate, Carbenes, NMR, Reaction Mechanisms. [Extracted from the article]

LEWIS acidity, CORANNULENE, POLYCYCLIC aromatic hydrocarbons, HELICENES, and ACENAPHTHENE

We have discovered a dual (i. e., soft and hard) Lewis acidity of alumina that enables rapid one‐pot π‐extension through the activation of terminal alkynes followed by C−F activation. The tandem reaction introduces an acenaphthene fragment – an essential moiety of geodesic polyarenes. This reaction provides quick access to elusive non‐alternant polyarenes such as π‐extended buckybowls and helicenes through three‐point annulation of the 1‐(2‐ethynyl‐6‐fluorophenyl)naphthalene moiety. The versatility of the developed method was demonstrated by the synthesis of unprecedented structural fragments of elusive geodesic graphene nanoribbons. [ABSTRACT FROM AUTHOR]

LEWIS acidity, CORANNULENE, and HELICENES

Keywords: alkyne activation; alumina; buckybowls; C-F activation; geodesic nanoribbons EN alkyne activation alumina buckybowls C-F activation geodesic nanoribbons 1 1 1 06/06/22 20220601 NES 220601 B Tandem bond activation b : The dual Lewis acidity of alumina has been discovered and employed to activate C-F and triple C C bonds in a tandem manner to provide rapid access to elusive nonplanar PAHs such as -extended helicenes, buckybowls and fragments of geodesic nanoribbons. Alkyne activation, alumina, buckybowls, C-F activation, geodesic nanoribbons. [Extracted from the article]

BIOSYNTHESIS, POSITRON emission tomography, HIPPOCAMPUS (Brain), SEROTONIN receptors, CENTRAL nervous system, LAMOTRIGINE, and RISPERIDONE

Efforts are underway to improve the diagnosis and treatment for neurological disorders like depression, anxiety, epilepsy, and schizophrenia. The G‐protein‐coupled receptors (GPCRs) 5‐HT7 receptor, the most recently identified member of 5‐HT receptor family dysregulation has an association with various central nervous system (CNS) disorders and its ligands have an edge as potential therapeutics. Here, we report the synthesis, characterization, and biological evaluation of diversely substituted methoxy derivatives of 2‐benzoxazolone arylpiperazine for targeting 5‐HT7 receptors. Out of all derivatives, only C‐2 substituted derivative, 3‐(4‐(4‐(2‐methoxyphenyl)piperazin‐1‐yl)butyl)benzoxazol‐2(3H)‐one/ABO demonstrate a high affinity for human 5‐HT7 receptors. [11C]ABO was obtained by O‐methylation of desmethyl‐precursor using [11C]CH3OTf in the presence of NaOH giving a high radiochemical yield of 25 ± 12% (decay‐corrected, n = 7) with stability up to 1.5 h postradiolabeling. In vitro autoradiography displays binding of [11C]ABO in accordance with 5‐HT7 distribution with a decrease of approximately 80% and 40% activity in the hippocampus and cerebellum brain region when administered with 10 µM cold ligand. Prefatory positron emission tomography scan results in Sprague‐Dawley (SD) rat brain revealed fast and high radioactivity build‐up in 5‐HT7 receptor‐rich regions, namely, the hippocampus (2.75 ± 0.16 SUV) and the cerebral cortex (2.27 ± 0.02 SUV) establishing selective targeting of [11C]ABO. In summary, these pieces of data designate [11C]ABO as a promising 5‐HT7 receptor ligand that can have possible roles in clinics after its further optimization on different animal models. [ABSTRACT FROM AUTHOR]

ORGANOSELENIUM compounds, POLYMERIZATION, and SELENIUM

The one-pot multicomponent synthetic strategy of organoselenium compounds represents an alternative and robust protocol to the conventional multistep methods. During the last decade, a potential advance has been made in this domain. This review discusses the latest advances in the polymerization, metal, and metal-free one-pot multicomponent synthesis of organoselenium compounds. [ABSTRACT FROM AUTHOR]

PARACYCLOPHANES, IONS, FLUOROPHORES, FLUORESCENCE, SKELETON, and MACROCYCLIC compounds

Transformation of [15]paracyclophanes ([15]PCP) into fluorophores has been achieved by embedding tetraphenylethene (TPE) units into their skeletons at the meso-positions. The obtained two hosts demonstrated distinct aggregation-induced emission (AIE) properties and their fluorescence could be selectively quenched by Ni2+ ions. [ABSTRACT FROM AUTHOR]

LIGNINS, MOLECULAR motor proteins, LIGNOCELLULOSE, TARGETED drug delivery, DRUG delivery systems, SOFT robotics, MOLECULAR switches, and LIGNIN structure

Lignin is the largest natural source of functionalized aromatics on the planet, therefore exploiting its inherent structural features for the synthesis of aromatic products is a timely and ambitious goal. While the recently developed lignin depolymerization strategies gave rise to well-defined aromatic platform chemicals, the diversification of these structures, especially toward high-end applications is still poorly addressed. Molecular motors and switches have found widespread application in many important areas such as targeted drug delivery systems, responsive coatings for self-healing surfaces, paints and resins or muscles for soft robotics. They typically comprise a functionalized aromatic backbone, yet their synthesis from lignin has not been considered before. In this contribution, we showcase the synthesis of a novel light-driven unidirectional molecular motor from the specific aromatic platform chemical 4-(3-hydroxypropyl)-2,6-dimethoxyphenol (dihydrosynapyl alcohol) that can be directly obtained from lignocellulose via a reductive catalytic fractionation strategy. The synthetic path takes into account the principles of green chemistry and aims to maintain the intrinsic functionality of the lignin-derived platform molecule. [ABSTRACT FROM AUTHOR]

ETHYL acetate, CERVICAL cancer, GRISEOFULVIN, CELL lines, XANTHONE, and CANCER cells

Chromatographic separation of the ethyl acetate extract of the root bark of Securidaca longipedunculata led to the isolation of one new xanthone derivative (1) along with nine known compounds (2-10). The structure of the isolated compounds were identified by NMR, mass spectrometric analyses, and comparison with the reported literature data. The isolates were evaluated for their cytotoxic activity with compounds 5 (IC50 = 0.38 µM) and 6 (IC50 = 52 µM) showed significant inhibitory activities against the human cervical cancer KB-3-1 cell line. Compound 5 displayed superior activity, which is even better than one of the reference drugs (griseofulvin, IC50 = 17 µM), whereas the rest showed little or none inhibitory activities. [ABSTRACT FROM AUTHOR]

ARGININE, DENSITY functional theory, FLUORESCENCE spectroscopy, ELECTROMAGNETIC spectrum, CARBOXYLATES, and SUPRAMOLECULAR chemistry

In this article, we present fluorescent guanidiniocarbonyl-indoles as versatile oxo-anion binders. Herein, the guanidiniocarbonyl-indole (GCI) and methoxy-guanidiniocarbonyl-indole (MGCI) were investigated as ethylamides and compared with the well-known guanidiniocarbonyl-pyrrole (GCP) concerning their photophysical properties as well as their binding behavior towards oxo-anions. Hence, a variety of anionic species, such as carboxylates, phosphonates and sulfonates, have been studied regarding their binding properties with GCP, GCI and MGCI using UV-Vis titrations, in combination with the determination of the complex stoichiometry using the Job method. The emission properties were studied in relation to the pH value using fluorescence spectroscopy as well as the determination of the photoluminescence quantum yields (PLQY). Density functional theory (DFT) calculations were undertaken to obtain a better understanding of the ground-lying electronic properties of the investigated oxo-anion binders. Additionally, X-ray diffraction of GCP and GCI was conducted. We found that GCI and MGCI efficiently bind carboxylates, phosphonates and sulfonates in buffered aqueous solution and in a similar range as GCP (Kass ≈ 1000–18,000 M−1, in bis-tris buffer, pH = 6); thus, they could be regarded as promising emissive oxo-anion binders. They also exhibit a visible fluorescence with a sufficient PLQY. Additionally, the excitation and emission wavelength of MGCI was successfully shifted closer to the visible region of the electromagnetic spectrum by introducing a methoxy-group into the core structure, which makes them interesting for biological applications. [ABSTRACT FROM AUTHOR]

QUINONE derivatives, MELTING points, INDOLE, THIN layer chromatography, and ORGANIC synthesis

12-Ethyl-6-methyliden-1,2,3,4,5,6-hexahydro-1,5-methanoazocino[4,3-b]indole-3-one (4) Methyllithium (10 mL, 3.0 M MeLi solution in THF) was added to a solution of compound B 3 b (1.5 g, 5.2 mmol) in 30 mL of anhydrous THF under a nitrogen atmosphere at 0 SP ° sp C and the mixture was stirred at 0 SP ° sp C for 1 h. The organic layer was dried over magnesium sulfate, filtered, and the solvent was evaporated to give an oil, which was purified by column chromatography (silica gel, ethyl acetate:acetone:triethylamine, 4:1:1). Finally, compound B 4 b was reduced with tris(triphenylphosphine)rhodium(I) carbonyl hydride in THF to give (±)-noruleine B 5 b in four steps, with an over-all yield of 41% and also obtained as yellow oil.[21],[22],[28] All of the component compounds in the preparative sequence were rigorously characterized (see Experimental section). The uleine alkaloids (Figure 1) have remarkable biological activities and have attracted much interest from synthetic organic chemists. [Extracted from the article]

NANOFIBERS, NERVOUS system regeneration, REGENERATION (Biology), NATURAL fibers, BONE cells, and EXTRACELLULAR matrix

Electrospun techniques are promising and flexible technologies to fabricate ultrafine fiber/nanofiber materials from diverse materials with unique characteristics under optimum conditions. These fabricated fibers/nanofibers via electrospinning can be easily assembled into several shapes of three-dimensional (3D) structures and can be combined with other nanomaterials. Therefore, electrospun nanofibers, with their structural and functional advantages, have gained considerable attention from scientific communities as suitable candidates in biomedical fields, such as the regeneration of tissues and organs, where they can mimic the network structure of collagen fiber in its natural extracellular matrix(es). Due to these special features, electrospinning has been revolutionized as a successful technique to fabricate such nanomaterials from polymer media. Therefore, this review reports on recent progress in electrospun nanofibers and their applications in various biomedical fields, such as bone cell proliferation, nerve regeneration, and vascular tissue, and skin tissue, engineering. The functionalization of the fabricated electrospun nanofibers with different materials furnishes them with promising properties to enhance their employment in various fields of biomedical applications. Finally, we highlight the challenges and outlooks to improve and enhance the application of electrospun nanofibers in these applications. [ABSTRACT FROM AUTHOR]