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Nicotinamide is an important functional compound and, in the form of nicotinamide adenine dinucleotide (NAD), is used as a co-factor by protein-based enzymes to catalyze redox reactions. In the context of the RNA world hypothesis, it is therefore reasonable to assume that ancestral ribozymes could have used co-factors such as NAD or its simpler analog nicotinamide riboside (NAR) to catalyze redox reactions. The only described example of such an engineered ribozyme uses a nicotinamide moiety bound to the ribozyme through non-covalent interactions. Covalent attachment of NAR to RNA could be advantageous, but the demonstration of such scenarios to date has suffered from the chemical instability of both NAR and its reduced form, NARH, making their use in oligonucleotide synthesis less straightforward. Here, we review the literature describing the chemical properties of the oxidized and reduced species of NAR, their synthesis, and previous attempts to incorporate either species into RNA. We discuss how to overcome the stability problem and succeed in generating RNA structures incorporating NAR. [ABSTRACT FROM AUTHOR]

The main feature of neurodegenerative diseases, including Alzheimer's disease, is the network of complex and not fully recognized neuronal pathways and targets involved in their onset and progression. The therapeutic treatment, at present mainly symptomatic, could benefit from a polypharmacological approach based on the development of a single molecular entity designed to simultaneously modulate different validated biological targets. This strategy is principally based on molecular hybridization, obtained by linking or merging different chemical moieties acting with synergistic and/or complementary mechanisms. The coumarin core, widely found in nature, endowed with a recognized broad spectrum of pharmacological activities, large synthetic accessibility and favourable pharmacokinetic properties, appears as a valuable, privileged scaffold to be properly modified in order to obtain compounds able to engage different selected targets. The scientific literature has long been interested in the multifaceted profiles of coumarin derivatives, and in this review, a survey of the most important results of the last four years, on both natural and synthetic coumarin-based compounds, regarding the development of anti-Alzheimer's compounds is reported. [ABSTRACT FROM AUTHOR]

Nickel-based catalysts are regarded as the most excellent urea oxidation reaction (UOR) catalysts in alkaline media. Whatever kind of nickel-based catalysts is utilized to catalyze UOR, it is widely believed that the in situ-formed Ni3+ moieties are the true active sites and the as-utilized nickel-based catalysts just serve as pre-catalysts. Digging the pre-catalyst effect on the activity of Ni3+ moieties helps to better design nickel-based catalysts. Herein, five different anions of OH−, CO32−, SiO32−, MoO42−, and WO42− were used to bond with Ni2+ to fabricate the pre-catalysts β-Ni(OH)2, Ni-CO3, Ni-SiO3, Ni-MoO4, and Ni-WO4. It is found that the true active sites of the five as-fabricated catalysts are the same in situ-formed Ni3+ moieties and the five as-fabricated catalysts demonstrate different UOR activity. Although the as-synthesized five catalysts just serve as the pre-catalysts, they determine the quantity of active sites and activity per active site, thus determining the catalytic activity of the catalysts. Among the five catalysts, the amorphous nickel tungstate exhibits the most superior activity per active site and can catalyze UOR to reach 158.10 mA·cm–2 at 1.6 V, exceeding the majority of catalysts. This work makes for a deeper understanding of the pre-catalyst effect on UOR activity and helps to better design nickel-based UOR catalysts. [ABSTRACT FROM AUTHOR]

N-aryl-substituted pyrrolidines are important moieties widely found in bioactive substances and drugs. Herein, we present a practical reductive amination of diketones with anilines for the synthesis of N-aryl-substituted pyrrolidines in good to excellent yields. In this process, the N-aryl-substituted pyrrolidines were furnished via successive reductive amination of diketones via iridium-catalyzed transfer hydrogenation. The scale-up performance, water as a solvent, simple operation, as well as derivation of drug molecules showcased the potential application in organic synthesis. [ABSTRACT FROM AUTHOR]

We present a systematic review of the methods developed for the synthesis of the aromathecin family of compounds (benz[6,7]indolizino[1,2-b]quinolin-11(13H)-ones) and their derivatives. These methods can be broadly classified into four categories based on the construction of pentacyclic structures: Category 1: by constructing a pyridone moiety (D-ring) on the pyrroloquinoline ring (A/B/C-ring), Category 2: by constructing a pyridine moiety (B-ring) on the pyrroloisoquinolone ring (C/D/E-ring), Category 3: by constructing an indolizidinone moiety (C/D-ring) in a tandem reaction, and Category 4: by constructing a pyrrolidine moiety (C-ring) on the isoquinolone ring (D/E-ring). [ABSTRACT FROM AUTHOR]

meso-Tetrahexylporphyrin was converted to its corresponding 7,8-dihydroxychlorin using an osmium tetroxide-mediated dihydroxylation strategy. Its diol moiety was shown to be able to undergo a number of subsequent oxidation reactions to form a chlorin dione and porpholactone, the first meso-alkylporphyrin-based porphyrinoid containing a non-pyrrolic building block. Further, the diol chlorin was shown to be susceptible to dehydration, forming the porphyrin enol that is in equilibrium with its keto-chlorin form. The meso-hexylchlorin dione could be reduced and it underwent mono- and bis-methylation reactions using methyl-Grignard reagents, and trifluoromethylation using the Ruppert-Prakash reagent. The optical and spectroscopic properties of the products are discussed and contrasted to their corresponding meso-aryl derivatives (where known). This contribution establishes meso-tetrahexyl-7,8-dihydroxychlorins as a new and versatile class of chlorins that is susceptible to a broad range of conversions to generate functionalized chlorins and a pyrrole-modified chlorin analogue. [ABSTRACT FROM AUTHOR]

The two star-shaped viologens containing 1,3,5-substituted phenyl (1) and triphenylamine (2) central cores and n-hexyl chains were synthesized and characterized. Both compounds exhibited promising optoelectronic properties and underwent multiple oxidation/reduction processes resulting in various colors. Four possible redox states of tripyridium salt containing a phenyl or triphenylamine core can occur depending on the applied potentials. The wide color range, from colorless through blue, azure to green-gray, was observed during the electrochemical reduction of compound 1. In the case of compound 2, the color change observed during spectroelectrochemical measurements was from yellow to colorless during the cathodic process and from yellow to green during the anodic process. The observed color change for both viologens was reversible. The triphenylamine-cored viologen (2) also exhibited emission in visible range and solvatochromism. It also exhibited luminescence in the solid state when excited with a UV lamp. These studies provide insights into the design of advanced materials for applications in displays. [ABSTRACT FROM AUTHOR]

The Rutaceae family is one of the most studied plant families due to the large number of alkaloids isolated from them with outstanding biological properties, among them the quinoline-based alkaloids Graveoline 1 and Dubamine 2. The most common methods for the synthesis of alkaloids 1 and 2 and their derivatives involves cycloaddition reactions or metal-catalyzed coupling processes but with some limitations in scope and functionalization of the quinoline moiety. As a continuation of our current studies on the synthesis and chemical transformation of 2-aminochalcones, we are reporting here an efficient metal-free approach for the total synthesis of alkaloids 1 and 2 along with their analogues with structural diversity, through a two-step sequence involving intramolecular cyclization, oxidation/aromatization, N-methylation and oxidative C-C bond processes, starting from dihydroquinolin-4-ones as common precursors for the construction of the structures of both classes of alkaloids. [ABSTRACT FROM AUTHOR]

Alantolactone is a eudesmane-type sesquiterpene lactone containing an α-methylene-γ-lactone moiety. Previous studies showed that alantolactone inhibits the nuclear factor κB (NF-κB) signaling pathway by targeting the inhibitor of NF-κB (IκB) kinase. However, in the present study, we demonstrated that alantolactone selectively down-regulated the expression of tumor necrosis factor (TNF) receptor 1 (TNF-R1) in human lung adenocarcinoma A549 cells. Alantolactone did not affect the expression of three adaptor proteins recruited to TNF-R1. The down-regulation of TNF-R1 expression by alantolactone was suppressed by an inhibitor of TNF-α-converting enzyme. Alantolactone increased the soluble forms of TNF-R1 that were released into the culture medium as an ectodomain. The structure–activity relationship of eight eudesmane derivatives revealed that an α-methylene-γ-lactone moiety was needed to promote TNF-R1 ectodomain shedding. In addition, parthenolide and costunolide, two sesquiterpene lactones with an α-methylene-γ-lactone moiety, increased the amount of soluble TNF-R1. Therefore, the present results demonstrate that sesquiterpene lactones with an α-methylene-γ-lactone moiety can down-regulate the expression of TNF-R1 by promoting its ectodomain shedding in A549 cells. [ABSTRACT FROM AUTHOR]

We previously revealed that phosphine–boranes can function as molecular frameworks for biofunctional molecules. In the present study, we exploited the diversity of available phosphines to design and synthesize a series of B-(trifluoromethyl)phenyl phosphine–borane derivatives as novel progesterone receptor (PR) antagonists. We revealed that the synthesized phosphine–borane derivatives exhibited LogP values in a predictable manner and that the P–H group in the phosphine–borane was almost nonpolar. Among the synthesized phosphine–boranes, which exhibited PR antagonistic activity, B-(4-trifluoromethyl)phenyl tricyclopropylphosphine–borane was the most potent with an IC50 value of 0.54 μM. A docking simulation indicated that the tricyclopropylphosphine moiety plays an important role in ligand–receptor interactions. These results support the idea that phosphine–boranes are versatile structural options in drug discovery, and the developed compounds are promising lead compounds for further structural development of next-generation PR antagonists. [ABSTRACT FROM AUTHOR]

The synthesis of hybrid molecules is one of the current strategies of drug discovery for the development of new lead compounds. The 1,2,3-triazole moiety represents an important building block in Medicinal Chemistry, extensively present in recent years. In this paper, we presented the design and the synthesis of new 1,2,3-triazole hybrids, containing both an isatine and a phenolic core. Firstly, the non-commercial azide and the alkyne synthons were prepared by different isatines and phenolic acids, respectively. Then, the highly regioselective synthesis of 1,4-disubstituted triazoles was obtained in excellent yields by a click chemistry approach, catalyzed by Cu(I). Finally, a molecular docking study was performed on the hybrid library, finding four different therapeutic targets. Among them, the most promising results were obtained on 5-lipoxygenase, an enzyme involved in the inflammatory processes. [ABSTRACT FROM AUTHOR]

The plant-derived toxin ricin is classified as a type 2 ribosome-inactivating protein (RIP) and currently lacks effective clinical antidotes. The toxicity of ricin is mainly due to its ricin toxin A chain (RTA), which has become an important target for drug development. Previous studies have identified two essential binding pockets in the active site of RTA, but most existing inhibitors only target one of these pockets. In this study, we used computer-aided virtual screening to identify a compound called RSMI-29, which potentially interacts with both active pockets of RTA. We found that RSMI-29 can directly bind to RTA and effectively attenuate protein synthesis inhibition and rRNA depurination induced by RTA or ricin, thereby inhibiting their cytotoxic effects on cells in vitro. Moreover, RSMI-29 significantly reduced ricin-mediated damage to the liver, spleen, intestine, and lungs in mice, demonstrating its detoxification effect against ricin in vivo. RSMI-29 also exhibited excellent drug-like properties, featuring a typical structural moiety of known sulfonamides and barbiturates. These findings suggest that RSMI-29 is a novel small-molecule inhibitor that specifically targets ricin toxin A chain, providing a potential therapeutic option for ricin intoxication. [ABSTRACT FROM AUTHOR]

In the present work, the synthesis of new ethacrynic acid (EA) derivatives containing nitrogen heterocyclic, urea, or thiourea moieties via efficient and practical synthetic procedures was reported. The synthesised compounds were screened for their anti-proliferative activity against two different cancer cell lines, namely, HL60 (promyelocytic leukaemia) and HCT116 (human colon carcinoma). The results of the in vitro tests reveal that compounds 1–3, 10, 16(a–c), and 17 exhibit potent anti-proliferative activity against the HL60 cell line, with values of the percentage of cell viability ranging from 20 to 35% at 1 μM of the drug and IC50 values between 2.37 μM and 0.86 μM. Compounds 2 and 10 showed a very interesting anti-proliferative activity of 28 and 48% at 1 μM, respectively, against HCT116. Two PyTAP-based fluorescent EA analogues were also synthesised and tested, showing good anti-proliferative activity. A test on the drug-likeness properties in silico of all the synthetised compounds was performed in order to understand the mechanism of action of the most active compounds. A molecular docking study was conducted on two human proteins, namely, glutathione S-transferase P1-1 (pdb:2GSS) and caspase-3 (pdb:4AU8) as target enzymes. The docking results show that compounds 2 and 3 exhibit significant binding modes with these enzymes. This finding provides a potential strategy towards developing anticancer agents, and most of the synthesised and newly designed compounds show good drug-like properties. [ABSTRACT FROM AUTHOR]

Amphiphilic fluorocarbon substances are a trending topic of research due to their wide range of applications accompanied by an alarming environmental and health impact. In order to predict their fate in the environment, use them more economically, develop new water treatment methods, etc., a better understanding of their physicochemical behavior is required. Their hydrophobicity in water/oil systems is particularly sensitive to one key thermodynamic parameter: the free energy of transfer of a perfluoromethylene group from oil to water. However, for the –CF2– moiety, the transfer energy values reported in the literature vary by more than ±25%. Due to the exponential relationship between this energy and the adsorption constants or the partition coefficients, such an uncertainty can lead to orders of magnitude error in the predicted distribution of fluorinated species. We address this problem by presenting an experimental determination of the hydrophobic effect of a –CF2– moiety with a greater certainty than currently available. The transfer energy is determined by measuring the interfacial tension of water|hexane for aqueous solutions of short-chained fluorotelomer alcohols. The obtained results for the free energy of transfer of a –CF2– moiety from oil to water are 1.68 ± 0.02 × R T 0 , 1.75 ± 0.02 × R T 0 , and 1.88 ± 0.02 × R T 0 at 288.15 K, 293.15 K, and 303.15 K, respectively. [ABSTRACT FROM AUTHOR]

A convenient protocol for the synthesis of 25,26,27-tribenzoyl-28-[((S)-1-diphenylphos- phanyl-propan-2-yl)oxy]-calix[4]arene via stereospecific methylation on Evans' oxazolidinone moiety was reported. According to the 13C NMR analysis of this phosphine, the calix[4]arene skeleton adopted a 1,3-alternate conformation. The latter conformation of the macrocycle and the (S)-chirality of the carbon atom bearing the methyl substituent were confirmed by a single-crystal X-ray diffraction study. After coordination of the phosphinated ligand to the dimeric [RuCl2(p-cymene)]2 organometallic precursor, the resulting arene–ruthenium complex was tested in the asymmetric reduction of acetophenone and alcohol was obtained with modest enantiomeric excess. [ABSTRACT FROM AUTHOR]

Molecular hybridization represents a new approach in drug discovery in which specific chromophores are strategically combined to create novel drugs with enhanced therapeutic effects. This innovative strategy leverages the strengths of individual chromophores to address complex biological challenges, synergize beneficial properties, optimize pharmacokinetics, and overcome limitations associated with single-agent therapies. Coumarins are documented to possess several bioactivities and have therefore been targeted for combination with other active moieties to create molecular hybrids. This review summarizes recent (2013–2023) trends in the synthesis of coumarins, as well as coumarin–chalcone and coumarin–triazole molecular hybrids. To cover the wide aspects of this area, we have included differently substituted coumarins, chalcones, 1,2,3– and 1,2,4–triazoles in this review and considered the point of fusion/attachment with coumarin to show the diversity of these hybrids. The reported syntheses mainly relied on well-established chemistry without the need for strict reaction conditions and usually produced high yields. Additionally, we discussed the bioactivities of the reported compounds, including antioxidative, antimicrobial, anticancer, antidiabetic, and anti-cholinesterase activities and commented on their IC50 where possible. Promising bioactivity results have been obtained so far. It is noted that mechanistic studies are infrequently found in the published work, which was also mentioned in this review to give the reader a better understanding. This review aims to provide valuable information to enable further developments in this field. [ABSTRACT FROM AUTHOR]

In this study, two previously undescribed nitrogen-containing compounds, penisimplicins A (1) and B (2), were isolated from Penicillium simplicissimum JXCC5. The structures of 1 and 2 were elucidated on the basis of comprehensive spectroscopic data analysis, including 1D and 2D NMR and HRESIMS data. The absolute configuration of 2 was determined by Marfey's method, ECD calculation, and DP4+ analysis. Both structures of 1 and 2 feature an unprecedented manner of amino acid-derivatives attaching to a polyketide moiety by C-C bond. The postulated biosynthetic pathways for 1 and 2 were discussed. Additionally, compound 1 exhibited significant acetylcholinesterase inhibitory activity, with IC50 values of 6.35 μM. [ABSTRACT FROM AUTHOR]

Quercetin is a flavonoid with significant biological and pharmacological activity. In this paper, quercetin was modified at the 3-OH position. Rutin was used as a raw material. We used methyl protection, Williamson etherification reactions, and then substitution reactions to prepare 15 novel quercetin derivatives containing a quinoline moiety. All these complexes were characterized by 1H NMR, 13C NMR, IR and HRMS. Of these, compound 3e (IC50 = 6.722 μmol·L−1) had a better inhibitory effect on human liver cancer (HepG-2) than DDP (Cisplatin) (IC50 = 26.981 μmol·L−1). The mechanism of the action experiment showed that compound 3e could induce cell apoptosis. [ABSTRACT FROM AUTHOR]

Quinoid single molecules are regarded as promising materials for electronic applications due to their tunable chemical structure-driven properties. A series of three single bio-inspired quinoid materials containing para-azaquinodimethane (p-AQM) moiety were designed, synthesized and characterized. AQM1, AQM2 and AQM3, prepared using aldehydes derived from almonds, corncobs and cinnamon, respectively, were studied as promising quinoid materials for optoelectronic applications. The significance of facile synthetic procedures is highlighted through a straightforward two-step synthesis, using Knoevenagel condensation. The synthesized molecules showed molar extinction coefficients of 22,000, 32,000 and 61,000 L mol−1 cm−1, respectively, for AQM1, AQM2 and AQM3. The HOMO-LUMO energy gaps were calculated experimentally, theoretically showing the same trends: AQM3 < AQM2 < AQM1. The role of the aryl substituent was studied and showed an impact on the electronic properties. DFT calculations show planar structures with quinoidal bond length alternation, in agreement with the experimental results. Finally, these bio-based materials showed high thermal stabilities between 290 °C and 340 °C and a glassy behavior after the first heating–cooling scan. These results highlight these bio-based single molecules as potential candidates for electronic or biomedical applications. [ABSTRACT FROM AUTHOR]

The piperazine moiety is often found in drugs or in bioactive molecules. This widespread presence is due to different possible roles depending on the position in the molecule and on the therapeutic class, but it also depends on the chemical reactivity of piperazine-based synthons, which facilitate its insertion into the molecule. In this paper, we take into consideration the piperazine-containing drugs approved by the Food and Drug Administration between January 2011 and June 2023, and the synthetic methodologies used to prepare the compounds in the discovery and process chemistry are reviewed. [ABSTRACT FROM AUTHOR]

An asymmetric aza-BODIPY analogue bearing quinoxaline moiety was synthesized via a titanium tetrachloride-mediated Schiff-base-forming reaction of 6,7-dimethyl-1,4-dihydroquinoxaline-2,3-dione and benzo[d]thiazol-2-amine. This novel aza-BODIPY analogue forms a complementary hydrogen-bonded dimer due to the quinoxaline moiety in the crystal structure. It also shows intense absorption and fluorescence, with fluorescence quantum yields close to unity. The electrochemical measurements and the DFT calculations revealed the presence of the low-lying HOMO, which benefits their potential applications as an electron-transporting material. [ABSTRACT FROM AUTHOR]

Block copolymers, known for their capacity to undergo microphase separation, spontaneously yield various periodic nanostructures. These precisely controlled nanostructures have attracted considerable interest due to their potential applications in microfabrication templates, conducting films, filter membranes, and other areas. However, it is crucial to acknowledge that microphase-separated structures typically exhibit random alignment, making alignment control a pivotal factor in functional material development. To address this challenge, researchers have explored the use of block copolymers containing liquid-crystalline (LC) polymers, which offer a promising technique for alignment control. The molecular structure and LC behavior of these polymers significantly impact the morphology and alignment of microphase-separated structures. In this study, we synthesized LC diblock copolymers with cyano-terminated phenyl benzoate moieties and evaluated the microphase-separated structures and molecular alignment behaviors. The LC diblock copolymers with a narrow molecular weight distribution were synthesized by atom transfer radical polymerization. Small angle X-ray scattering measurements revealed that the block copolymers exhibit smectic LC phases and form cylinder structures with a lattice period of about 18 nm by microphase separation. The examination of block copolymer films using polarized optical microscopy and polarized UV-visible absorption spectroscopy corroborated that the LC moieties were uniaxially aligned along the alignment treatment direction. [ABSTRACT FROM AUTHOR]

An efficient method of accessing new CF3-containing spiro-[indene-proline] derivatives has been developed based on a Cp*Rh(III)-catalyzed tandem C-H activation/[3+2]–annulation reaction of 5-aryl-2-(trifluoromethyl)-3,4-dihydro-2H-pyrrole-2-carboxylates with alkynes. An important feature of this spiro annulation process is the feasibility of dehydroproline moiety to act as a directing group in the selective activation of the aromatic C-H bond. [ABSTRACT FROM AUTHOR]

Many biological functions of curcumin have been reported. As certain bioactivities of curcumin are eliminated by antioxidants, reactive oxygen species generated by curcumin have been suggested as a relevant mechanism. In the present study, the effects of different types of antioxidants on the stability and bioactivities of curcumin were analyzed. High concentrations (>4 mM) of thiol antioxidants, including N-acetylcysteine (NAC), glutathione (GSH), and β-mercaptoethanol, accelerated the decomposition of curcumin and other curcuminoids; the submillimolar levels (<0.5 mM) of GSH and NAC rather improved their stability. Ascorbic acid or superoxide dismutase also stabilized curcumin, regardless of their concentration. The cellular levels and bioactivities of curcumin, including its cytotoxicity and the induction of heme oxygenase-1, were significantly reduced in the presence of 8 mM of GSH and NAC. The effects were enhanced in the presence of submillilmolar GSH and NAC, or non-thiol antioxidants. The present results indicate that antioxidants with a reduced thiol group could directly interact with the α,β-unsaturated carbonyl moiety of curcuminoids and modulate their stability and bioactivity. [ABSTRACT FROM AUTHOR]

An undescribed diterpene, stellerterpenoid A (1), and two undescribed sesquiterpenoids, stellerterpenoids B and C (2–3), together with six known compounds, prostratin (4) stelleraguaianone B (5), chamaejasnoid A (6), auranticanol L (7), wikstronone C (8), and oleodaphnone (9), were isolated from the roots of Stellera chamaejasme L. Their structures were elucidated by extensive spectroscopic data (1D, 2D NMR, IR, UV, and HR-ESI-MS). The absolute configuration of 1–3 was elucidated based on ECD calculation. Among them, stellerterpenoid A was a rare 13, 14-seco nortigliane diterpenoid and stellerterpenoid B was a guaiacane-type sesquiterpenoid with an unusual 1, 2-diketone moiety. The known stelleraguaianone B (5) exhibited moderate activity for suppressing NO production in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages cells with an IC50 value of 24.76 ± 0.4 μM. None of the compounds showed anti-influenza virus or anti-tumor activity in vitro. [ABSTRACT FROM AUTHOR]

(−)-5,9-Dimethyl-6,7-benzomorphan (normetazocine) derivatives with a para-OH or ortho-F substituent in the aromatic ring of the N-phenethyl moiety were synthesized and found to have subnanomolar potency at MOR, and both were fully efficacious in vitro. These new compounds, (1R,5R,9R)-6,11-dimethyl-3-(2-fluorophenethyl)-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocin-8-ol and (1R,5R,9R)-6,11-dimethyl-3-(4-hydroxyphenethyl)-1,2,3,4,5,6-hexahydro-2,6-methanobenzo[d]azocin-8-ol, were more potent than the unsubstituted compound N-phenethylnormetazocine and about 30 or 40 times more potent than morphine, respectively. A variety of substituents in the ortho, meta, or para position in the aromatic ring of the N-phenethyl moiety were synthesized, 25 of these compounds, and found to have varying effects on potency and efficacy as determined by the forskolin-induced cAMP accumulation assay. The N-phenethyl moiety was also modified by increasing chain length to form a N-phenylpropyl side chain with and without a para-nitro moiety, and by an N-cinnamyl side chain. Also, an indole ethylamine normetazocine was synthesized to replace the N-phenethylamine side chain in normetazocine. The phenylpropylamine, propenylamine (cinnamyl) and the para-nitropropylamine had little or no MOR potency. The indole-ethylamine on the normetazocine nucleus, however, had moderate potency (MOR EC50 = 12 nM), and was fully efficacious (%Emax = 102%) in the cAMP assay. Retention of the N-phenethyl moiety and the addition of alkyl and alkenyl moieties on C8 in (−)-N-phenethylnormetazocine gave a C8-methylene derivative that had subnanomolar potency at MOR and a C8-methyl analog that had nanomolar potency. Five C8-substituted compounds were synthesized. [ABSTRACT FROM AUTHOR]

Crop fungal diseases pose a serious threat to global crop production and quality. Developing new and efficient fungicides is an important measure to control crop diseases. Phenylthiazole was found to be an excellent antifungal skeleton based on our previous study on the structural optimization and biological activity of the natural product thiasporine A. To find new fungicides, 45 phenylthiazole derivatives containing an acylhydrazone moiety were designed and synthesized by the principle of active substructure splicing. Forty-two of the forty-five compounds are novel, except for compounds E1, E14, and E33. Their structures were structurally characterized by 1H NMR, 13C NMR, and HRMS. The antifungal activities of the target compounds against Magnaporthe oryzae Colletotrichum camelliaet, Bipolaris maydis, and Sclerotinia sclerotiorum were evaluated at 25 μg/mL. The bioassay results revealed that most of these compounds exhibited excellent antifungal activities against M. oryzae and C. camelliaet at 25 μg/mL. In particular, compounds E4, E10, E14, E17, E23, E26, and E27 showed the inhibition rate of more than 80% against M. oryzae, with EC50 values of 1.66, 2.01, 2.26, 1.45, 1.50, 1.29, and 2.65 μg/mL, respectively, which were superior to that of the commercial fungicides Isoprothiolane (EC50 = 3.22 μg/mL) and Phenazine-1-carboxylic acid (EC50 = 27.87 μg/mL). The preliminary structure–activity relationship (SAR) results suggested that introducing methyl, halogen, or methoxy at the ortho-position of R1 and the para-position of R2 can endow the final structure with excellent antifungal activity against M. oryzae. The current results provide useful data for developing phenylthiazole derivatives as new fungicides for controlling rice blast caused by M. oryzae. [ABSTRACT FROM AUTHOR]

The enzymatic transformation of the sugar moiety of the gypenosides provides a new way to obtain more pharmacologically active components. A gene encoding a family 1 glycosyl hydrolase from Bifidobacterium dentium was cloned and expressed in Escherichia coli. The recombinant enzyme was purified, and its molecular weight was approximately 44 kDa. The recombinant BdbglB exhibited an optimal activity at 35 °C and pH 5.4. The purified recombinant enzyme, exhibiting β-glucosidase activity, was used to produce gypenoside XVII (Gyp XVII) via highly selective and efficient hydrolysis of the outer glucose moiety linked to the C-3 position in ginsenoside Rb1 (G-Rb1). Under the optimal reaction conditions for large scale production of gypenoside XVII, 40 g ginsenoside Rb1 was transformed by using 45 g crude enzyme at pH 5.4 and 35 °C for 10 h with a molar yield of 100%. Furthermore, the anti-inflammatory effects of the product gypenoside XVII and its conversion precursor ginsenoside Rb1 were evaluated by using lipopolysaccharide (LPS)-induced murine RAW 264.7 macrophages and the xylene-induced acute inflammation model of mouse ear edema, respectively. Gypenoside XVII showed improved anti-inflammatory activity, which significantly inhibited the generation of TNF-α and IL-6 more effectively than its precursor ginsenoside Rb1. In addition, the swelling inhibition rate of gypenoside XVII was 80.55%, while the rate of its precursor was 40.47%, the results also indicated that gypenoside XVII had better anti-inflammatory activity than ginsenoside Rb1. Hence, this enzymatic method would be useful in the large-scale production of gypenoside XVII, which may become a new potent anti-inflammatory candidate drug. [ABSTRACT FROM AUTHOR]

2-Propargyl-1,3-dicarbonyl compounds have been carbonylated under oxidative conditions and with the catalysis of the PdI2/KI catalytic system to selectively afford previously unreported 2-(4-acylfuran-2-yl)acetamides in fair to good yields (54–81%) over 19 examples. The process takes place under relatively mild conditions and occurs via a mechanistic pathway involving Csp-H activation by oxidative monoamincarbonylation of the terminal triple bond of the substrates with formation of 2-ynamide intermediates, followed by 5-exo-dig O-cyclization (via intramolecular conjugate addition of the in situ formed enolate to the 2-ynamide moiety) and aromative isomerization. [ABSTRACT FROM AUTHOR]

Asiatic acid, a pentacyclic triterpene, was converted into a series of piperazinyl, homopiperazinyl, and 1,5-diazocinyl spacered rhodamine conjugates, differing in the type of spacer and the substitution pattern on the rhodamine moiety of the hybrids. The compounds were tested for cytotoxic activity in SRB assays and compound 12, holding an EC50 of 0.8 nM, was the most cytotoxic compound of this series, but compound 18 (containing a ring expanded 1,5-diazocinyl moiety and n-propyl substituents on the rhodamine) was the most selective compound exhibiting a selectivity factor of almost 190 while retaining high cytotoxicity (EC50 = 1.9 nM, for A2780 ovarian carcinoma). [ABSTRACT FROM AUTHOR]

The review covers more than a century of decaborane chemistry from the first synthesis by Alfred Stock to the present day. The main attention is paid to the reactions of the substitution of hydrogen atoms by various atoms and groups with the formation of exo-polyhedral boron–halogen, boron–oxygen, boron–sulfur, boron–nitrogen, boron–phosphorus, and boron–carbon bonds. Particular attention is paid to the chemistry of conjucto-borane anti-[B18H22], whose structure is formed by two decaborane moieties with a common edge, the chemistry of which has been intensively developed in the last decade. [ABSTRACT FROM AUTHOR]

Free radicals and oxidants may cause various damages both to the lifeworld and different products. A typical solution for the prophylaxis of oxidation-caused conditions is the usage of various antioxidants. Among them, various classes are found—polyphenols, conjugated polyalkenes, and some sulfur and nitrogen derivatives. Regarding the active site in the molecules, a widely discussed group of compounds are 1,3-dicarbonyl compounds. Among them are natural (e.g., curcumin and pulvinic acids) and synthetic (e.g., 4-hydroxy coumarins, substituted Meldrum's acids) compounds. Herein, information about various compounds containing the 1,3-dicarbonyl moiety is covered, and their antiradical and antioxidant activity, depending on the structure, is discussed. [ABSTRACT FROM AUTHOR]

Tolyporphins were discovered some 30 years ago as part of a global search for antineoplastic compounds from cyanobacteria. To date, the culture HT-58-2, comprised of a cyanobacterium–microbial consortium, is the sole known producer of tolyporphins. Eighteen tolyporphins are now known—each is a free base tetrapyrrole macrocycle with a dioxobacteriochlorin (14), oxochlorin (3), or porphyrin (1) chromophore. Each compound displays two, three, or four open β-pyrrole positions and two, one, or zero appended C-glycoside (or –OH or –OAc) groups, respectively; the appended groups form part of a geminal disubstitution motif flanking the oxo moiety in the pyrroline ring. The distinct structures and repertoire of tolyporphins stand alone in the large pigments-of-life family. Efforts to understand the cyanobacterial origin, biosynthetic pathways, structural diversity, physiological roles, and potential pharmacological properties of tolyporphins have attracted a broad spectrum of researchers from diverse scientific areas. The identification of putative biosynthetic gene clusters in the HT-58-2 cyanobacterial genome and accompanying studies suggest a new biosynthetic paradigm in the tetrapyrrole arena. The present review provides a comprehensive treatment of the rich science concerning tolyporphins. [ABSTRACT FROM AUTHOR]

The current work was conducted to synthesize several novel anti-inflammatory quinazolines having sulfamerazine moieties as new 3CLpro, cPLA2, and sPLA2 inhibitors. The thioureido derivative 3 was formed when compound 2 was treated with sulfamerazine. Also, compound 3 was reacted with NH2-NH2 in ethanol to produce the N-aminoquinazoline derivative. Additionally, derivative 4 was reacted with 4-hydroxy-3-methoxybenzaldehyde, ethyl chloroacetate, and/or diethyl oxalate to produce quinazoline derivatives 5, 6, and 12, respectively. The results of the pharmacological study indicated that the synthesized 4–6 and 12 derivatives showed good 3CLpro, cPLA2, and sPLA2 inhibitory activity. The IC50 values of the target compounds 4–6, and 12 against the SARS-CoV-2 main protease were 2.012, 3.68, 1.18, and 5.47 µM, respectively, whereas those of baicalein and ivermectin were 1.72 and 42.39 µM, respectively. The IC50 values of the target compounds 4–6, and 12 against sPLA2 were 2.84, 2.73, 1.016, and 4.45 µM, respectively, whereas those of baicalein and ivermectin were 0.89 and 109.6 µM, respectively. The IC50 values of the target compounds 4–6, and 12 against cPLA2 were 1.44, 2.08, 0.5, and 2.39 µM, respectively, whereas those of baicalein and ivermectin were 3.88 and 138.0 µM, respectively. Also, incubation of lung cells with LPS plus derivatives 4–6, and 12 caused a significant decrease in levels of sPLA2, cPLA2, IL-8, TNF-α, and NO. The inhibitory activity of the synthesized compounds was more pronounced compared to baicalein and ivermectin. In contrast to ivermectin and baicalein, bioinformatics investigations were carried out to establish the possible binding interactions between the newly synthesized compounds 2–6 and 12 and the active site of 3CLpro. Docking simulations were utilized to identify the binding affinity and binding mode of compounds 2–6 and 12 with the active sites of 3CLpro, sPLA2, and cPLA2 enzymes. Our findings demonstrated that all compounds had outstanding binding affinities, especially with the key amino acids of the target enzymes. These findings imply that compound 6 is a potential lead for the development of more effective SARS-CoV-2 Mpro inhibitors and anti-COVID-19 quinazoline derivative-based drugs. Compound 6 was shown to have more antiviral activity than baicalein and against 3CLpro. Furthermore, the IC50 value of ivermectin against the SARS-CoV-2 main protease was revealed to be 42.39 µM, indicating that it has low effectiveness. [ABSTRACT FROM AUTHOR]

In the past half-century, macrocycles with different structures and functions, have played a critical role in supramolecular chemistry. Two macrocyclic moieties can be linked to form bismacrocycle molecules. Compared with monomacrocycle, the unique structures of bismacrocycles led to their specific recognition and assembly properties, also a wide range of applications, including molecular recognition, supramolecular self-assembly, advanced optical material construction, etc. In this review, we focus on the structure of bismacrocycle and their applications. Our goal is to summarize and outline the possible future development directions of bismacrocycle research. [ABSTRACT FROM AUTHOR]

Organotin (IV) dithiocarbamate has recently received attention as a therapeutic agent among organotin (IV) compounds. The individual properties of the organotin (IV) and dithiocarbamate moieties in the hybrid complex form a synergy of action that stimulates increased biological activity. Organotin (IV) components have been shown to play a crucial role in cytotoxicity. The biological effects of organotin compounds are believed to be influenced by the number of Sn-C bonds and the number and nature of alkyl or aryl substituents within the organotin structure. Ligands target and react with molecules while preventing unwanted changes in the biomolecules. Organotin (IV) dithiocarbamate compounds have also been shown to have a broad range of cellular, biochemical, and molecular effects, with their toxicity largely determined by their structure. Continuing the investigation of the cytotoxicity of organotin (IV) dithiocarbamates, this mini-review delves into the appropriate method for synthesis and discusses the elemental and spectroscopic analyses and potential cytotoxic effects of these compounds from articles published since 2010. [ABSTRACT FROM AUTHOR]

The first access to polyfunctionnalized pyrrolo[3,4-c]pyrazole-4,6-(2H,5H)-dione derivatives is reported. The series were generated from diethyl acetylenedicarboxylate and arylhydrazines, which afforded the key intermediates bearing two functional positions. The annellation to generate the maleimide moiety of the bicycle was studied. Moreover, an efficient palladium-catalyzed C-C and C-N bond formation via Suzuki–Miyaura or Buchwald–Hartwig coupling reactions in C-6 position was investigated from 6-chloropyrrolo[3,4-c]pyrazole-4,6-(2H,5H)–diones. This method provides novel access to various 1,6 di-substituted pyrrolo[3,4-c] pyrazole-4,6-(2H,5H)–diones. [ABSTRACT FROM AUTHOR]

The roots of Astilbe grandis, known as "Ma sang gou bang", are used as a Miao traditional medicine with anti-inflammatory and analgesic properties. However, the active components and mechanism of action of this plant remain mostly uncharacterized. The aim of this study was to identify its active components and verify their pharmacological activity. The extract of A. grandis root was separated using various chromatographic methods. As a result, we obtained one novel triterpenoid, named astigranlactone (1), which has an unusual lactone moiety formed between C-7 and C-27. Additionally, a known coumarin compound, 11-O-galloyl bergenin (2) was isolated from this plant. The structures of these two compounds were elucidated by extensive NMR experiments in conjunction with HR-ESI-MS data. To the best of our knowledge, both compounds were isolated from this species for the first time. Moreover, we tested the anti-inflammation effect of the two compounds by establishing a cellular inflammation model induced by LPS in RAW264.7 cells. The effect of different concentrations of these compounds on the activity of RAW264.7 cells was assessed using a CCK8 assay. The levels of nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in the supernatant of each group were evaluated using the Griess method and an enzyme-linked immunosorbent assay (ELISA). Western blot and quantitative real-time PCR (qRT-RCR) were used to measure the levels of cyclooxygenase 2 (COX-2) and nitric oxide synthase (iNOS) gene expression. Our findings revealed that these two compounds inhibited the high levels of NO, TNF-α, IL-6, IL-1β, COX-2, and iNOS (induced by LPS). Mechanistic studies demonstrated that these two compounds reduced the activation of the nuclear transcription factor-B (NF-κB) signaling pathway by inhibiting the phosphorylation of p65. Therefore, our study indicates that compounds 1 and 2 can exert a definite anti-inflammatory effect by inhibiting the NF-κB signaling pathway. [ABSTRACT FROM AUTHOR]

Four new meroterpenoids, Clavilactone M-P, possessing novel aminoglycoside moiety (1–4) and a 10-membered carbocycle fused with an α,β-epoxy-γ-lactone, were isolated from Clitocybe clavipes, a basidiomycete. Their structures with absolute configurations were determined by extensive analysis of their spectroscopic data, and the ECD method. All the isolated compounds (1–4) were evaluated for their antitumor activity against three human cancer cell lines using the MTT assay. Compound 1 and 2 exhibited a significant suppression of cell viability in the Hela (IC50 = 22.8 and 19.7 μM) cell line. [ABSTRACT FROM AUTHOR]

Highlights: What are the main findings? The ME molecule has 21 stable configurations. For all the tops (except =CH2), the barrier heights are of the same order, while the =CH2 top has a barrier height one order of magnitude higher. Like estragole and eugenol, ME also has the same Fermi doublets for the following modes: νs(–CH2) and 2 × βs(–CH2); νs(CH3) and 2 × δs(CH3). The ME molecule has three active sites. Vibrational analysis suggests that the solvents affect the internal modes of both OCH3 moieties strongly. What is the implication of the main finding? The methyl-eugenol molecule could be a good choice for the pharmacological applications The OCH3 moieties of methyl-eugenol play significant role in interaction with other molecules. Structural, conformational, and spectroscopic investigations of methyl-eugenol were made theoretically at the B3LYP-6-311++G**level. Experimental IR, Raman, and UV-vis spectra were investigated and analyzed in light of the computed quantities. Conformational analysis was carried out with the help of total energy vs. dihedral angle curves for different tops, yielding 21 stable conformers, out of which only two have energies below the room temperature relative to the lowest energy conformer. The effect of the solvent on different molecular characteristics was investigated theoretically. MEP and HOMO-LUMO analysis were carried out and barrier heights and bioactivity scores were determined. The present investigation suggests that the molecule has three active sites with moderate bioactivity. The solvent–solute interaction is found to be dominant in the vicinity of the methoxy moieties. [ABSTRACT FROM AUTHOR]

Mo/W-containing formate dehydrogenases (FDH) catalyzes the reversible oxidation of formate to carbon dioxide at their molybdenum or tungsten active sites. The metal-containing FDHs are members of the dimethylsulfoxide reductase family of mononuclear molybdenum cofactor (Moco)- or tungsten cofactor (Wco)-containing enzymes. In these enzymes, the active site in the oxidized state comprises a Mo or W atom present in the bis-Moco, which is coordinated by the two dithiolene groups from the two MGD moieties, a protein-derived SeCys or Cys, and a sixth ligand that is now accepted as being a sulfido group. SeCys-containing enzymes have a generally higher turnover number than Cys-containing enzymes. The analogous chemical properties of W and Mo, the similar active sites of W- and Mo-containing enzymes, and the fact that W can replace Mo in some enzymes have led to the conclusion that Mo- and W-containing FDHs have the same reaction mechanism. Details of the catalytic mechanism of metal-containing formate dehydrogenases are still not completely understood and have been discussed here. [ABSTRACT FROM AUTHOR]

This study presents the synthesis and characterization of two spirobifluorenyl derivatives substituted with either triphenylmethyl (SB-C) or triphenylsilyl (SB-Si) moieties for use as host materials in phosphorescent organic light-emitting diodes (PHOLED). Both molecules have similar high triplet energies and large energy gaps. Blue Ir(tpz)3 and green Ir(ppy)3 phosphorescent devices were fabricated using these materials as hosts. Surprisingly, SB-Si demonstrated superior charge-transporting ability compared to SB-C, despite having similar energies for their valence orbitals. In particular, SB-Si proved to be a highly effective host for both blue and green devices, resulting in maximum efficiencies of 12.6% for the Ir(tpz)3 device and 9.6% for the Ir(ppy)3 device. These results highlight the benefits of appending the triphenylsilyl moiety onto host materials and underscore the importance of considering the morphology of hosts in the design of efficient PHOLEDs. [ABSTRACT FROM AUTHOR]

The design of highly efficient sensitizers is one of the most significant areas in dye-sensitized solar cell (DSSC) research. We studied a series of benzothiadiazole-based D-π-π-A organic dyes, putting emphasis on the influence of the donor moiety on the DSSC's efficiency. Using (linear-response time-dependent) density functional theory ((TD)DFT)) with the CAM-B3LYP functional, different donor groups were characterized in terms of electronic absorption spectra and key photovoltaic parameters. As a reference, a dye was considered that had a benzothiadiazole fragment linked via thiophene rings to a diphenylamine donor and a cyanoacrylic-acid acceptor. The different systems were first studied in terms of individual performance parameters, which eventually aggregated into power conversion efficiency. Only the amino-substituted species showed a modest increase, whereas the dimethylamino case showed a decrease. [ABSTRACT FROM AUTHOR]

We previously reported dipeptidomimetic compounds as inhibitors of neuronal and/or inducible NO synthases (n/iNOS) with significant selectivity against endothelial NOS (eNOS). They were composed of an S-ethylisothiocitrullin-like moiety linked to an extension through a peptide bond or a 1,2,4-oxadiazole link. Here, we developed two further series where the extension size was increased to establish more favorable interactions in the NOS substrate access channel. The extension was introduced on the solid phase by the reductive alkylation of an amino-piperidine moiety or an aminoethyl segment in the case of dipeptide-like and 1,2,4-oxadiazole compounds, respectively, with various benzaldehydes. Compared to the previous series, more potent inhibitors were identified with IC50 in the micromolar to the submicromolar range, with significant selectivity toward nNOS. As expected, most compounds did not inhibit eNOS, and molecular modeling was carried out to characterize the reasons for the selectivity toward nNOS over eNOS. Spectral studies showed that compounds were interacting at the heme active site. Finally, selected inhibitors were found to inhibit intra-cellular iNOS and nNOS expressed in RAW264.7 and INS-1 cells, respectively. [ABSTRACT FROM AUTHOR]

[1,3,5]Triazino[1,2-a]benzimidazole-2-amines bearing heterocyclic moiety in 4-position were synthesized. The compounds were characterized by elemental analysis, IR, 1H-NMR, 13C-NMR, and HRMS spectroscopy. The molecular geometry and electron structure of these molecules were theoretically studied using density functional theory (DFT) methods. The molecular structure of the synthesized fused triazinobenzimidazole was confirmed to correspond to the 3,4-dihydrotriazinobenzimidazole structure through the analysis of spectroscopic NMR data and DFT calculations. The antinematodic activity was evaluated in vitro on isolated encapsulated muscle larvae (ML) of Trichinella spiralis. The results showed that the tested triazinobenzimidazoles exhibit significantly higher efficiency than the conventional drug used to treat trichinosis, albendazole, at a concentration of 50 μg/mL. The compound 3c substituted with a thiophen-2-yl moiety exhibited the highest anthelmintic activity, with a larvicidal effect of 58.41% at a concentration of 50 μg/mL after 24 h of incubation. Following closely behind, the pyrrole analog 3f demonstrated 49.90% effectiveness at the same concentration. The preliminary structure-anti-T. spiralis activity relationship (SAR) of the analogues in the series was discussed. The cytotoxicity of the benzimidazole derivatives against two normal fibroblast cells (3T3 and CCL-1) and two cancer human cell lines (MCF-7 breast cancer cells and chronic myeloid leukemia cells AR-230) was evaluated using the MTT-dye reduction assay. The screening results indicated that the compounds showed no cytotoxicity against the tested cell lines. An in silico study of the physicochemical and pharmacokinetic characteristics of the novel synthesized fused triazinobenzimidazoles showed that they were characterized by a significant degree of drug-likeness and optimal properties for anthelmintic agents. [ABSTRACT FROM AUTHOR]

Oxime ethers are a class of compounds containing the >C=N-O-R moiety. The presence of this moiety affects the biological activity of the compounds. In this review, the structures of oxime ethers with specific biological activity have been collected and presented, and bactericidal, fungicidal, antidepressant, anticancer and herbicidal activities, among others, are described. The review includes both those substances that are currently used as drugs (e.g., fluvoxamine, mayzent, ridogrel, oxiconazole), as well as non-drug structures for which various biological activity studies have been conducted. To the best of our knowledge, this is the first review of the biological activity of compounds containing such a moiety. The authors hope that this review will inspire scientists to take a greater interest in this group of compounds, as it constitutes an interesting research area. [ABSTRACT FROM AUTHOR]

Twenty-four new phenylpropanoid esters of sucrose, phanerosides A–X (1–24), were isolated from an EtOH extract of the rattans of Phanera championii Benth. (Fabaceae). Their structures were elucidated on the basis of comprehensive spectroscopic data analysis. A wide range of structural analogues were presented due to the different numbers and positions of acetyl substituents and the structures of phenylpropanoid moieties. Phenylpropanoid esters of sucrose were isolated from the Fabaceae family for the first time. Biologically, the inhibitory effects of compounds 6 and 21 on NO production in LPS-induced BV-2 microglial cells were better than that of the positive control, with IC50 values of 6.7 and 5.2 μM, respectively. The antioxidant activity assay showed that compounds 5, 15, 17, and 24 displayed moderate DPPH radical scavenging activity, with IC50 values ranging from 34.9 to 43.9 μM. [ABSTRACT FROM AUTHOR]

A series of tetracationic bis-triarylborane dyes, differing in the aromatic linker connecting two dicationic triarylborane moieties, showed very high submicromolar affinities toward ds-DNA and ds-RNA. The linker strongly influenced the emissive properties of triarylborane cations and controlled the fluorimetric response of dyes. The fluorene-analog shows the most selective fluorescence response between AT-DNA, GC-DNA, and AU-RNA, the pyrene-analog's emission is non-selectively enhanced by all DNA/RNA, and the dithienyl-diketopyrrolopyrrole analog's emission is strongly quenched upon DNA/RNA binding. The emission properties of the biphenyl-analog were not applicable, but the compound showed specific induced circular dichroism (ICD) signals only for AT-sequence-containing ds-DNAs, whereas the pyrene-analog ICD signals were specific for AT-DNA with respect to GC-DNA, and also recognized AU-RNA by giving a different ICD pattern from that observed upon interaction with AT-DNA. The fluorene- and dithienyl-diketopyrrolopyrrole analogs were ICD-signal silent. Thus, fine-tuning of the aromatic linker properties connecting two triarylborane dications can be used for the dual sensing (fluorimetric and CD) of various ds-DNA/RNA secondary structures, depending on the steric properties of the DNA/RNA grooves. [ABSTRACT FROM AUTHOR]

A few α-glucan debranching enzymes (DBEs) of the large glycoside hydrolase family 13 (GH13), also known as the α-amylase family, have been shown to catalyze transglycosylation as well as hydrolysis. However, little is known about their acceptor and donor preferences. Here, a DBE from barley, limit dextrinase (HvLD), is used as a case study. Its transglycosylation activity is studied using two approaches; (i) natural substrates as donors and different p-nitrophenyl (pNP) sugars as well as different small glycosides as acceptors, and (ii) α-maltosyl and α-maltotriosyl fluorides as donors with linear maltooligosaccharides, cyclodextrins, and GH inhibitors as acceptors. HvLD showed a clear preference for pNP maltoside both as acceptor/donor and acceptor with the natural substrate pullulan or a pullulan fragment as donor. Maltose was the best acceptor with α-maltosyl fluoride as donor. The findings highlight the importance of the subsite +2 of HvLD for activity and selectivity when maltooligosaccharides function as acceptors. However, remarkably, HvLD is not very selective when it comes to aglycone moiety; different aromatic ring-containing molecules besides pNP could function as acceptors. The transglycosylation activity of HvLD can provide glycoconjugate compounds with novel glycosylation patterns from natural donors such as pullulan, although the reaction would benefit from optimization. [ABSTRACT FROM AUTHOR]

The tropylium ion is a non-benzenoid aromatic species that works as a catalyst. This chemical entity brings about a large number of organic transformations, such as hydroboration reactions, ring contraction, the trapping of enolates, oxidative functionalization, metathesis, insertion, acetalization, and trans-acetalization reactions. The tropylium ion also functions as a coupling reagent in synthetic reactions. This cation's versatility can be seen in its role in the synthesis of macrocyclic compounds and cage structures. Bearing a charge, the tropylium ion is more prone to nucleophilic/electrophilic reactions than neutral benzenoid equivalents. This ability enables it to assist in a variety of chemical reactions. The primary purpose of using tropylium ions in organic reactions is to replace transition metals in catalysis chemistry. It outperforms transition-metal catalysts in terms of its yield, moderate conditions, non-toxic byproducts, functional group tolerance, selectivity, and ease of handling. Furthermore, the tropylium ion is simple to synthesize in the laboratory. The current review incorporates the literature reported from 1950 to 2021; however, the last two decades have witnessed a phenomenal upsurge in the utilization of the tropylium ion in the facilitation of organic conversions. The importance of the tropylium ion as an environmentally safe catalyst in synthesis and a comprehensive summary of some important reactions catalyzed via tropylium cations are described. [ABSTRACT FROM AUTHOR]