Acetamido Group Research Articles

Revealing the Structure of Sheer N-Acetylglucosamine, an Essential Chemical Scaffold in Glycobiology.

We explored the conformational landscape of N-acetyl-α-d-glucosamine (α-GlcNAc), a fundamental chemical scaffold in glycobiology. Solid samples were vaporized by laser ablation, expanded in a supersonic jet, and characterized by broadband chirped pulse Fourier transform microwave spectroscopy. In the isolation conditions of the jet, three different structures of GlcNAc have been discovered. These are conclusively identified by comparing the experimental values of the rotational constants with those predicted by theoretical calculations. The conformational preferences are controlled by intramolecular hydrogen bond networks formed between the polar groups in the acetamido group and the hydroxyl groups and dominated in all cases by a strong OH···O═C interaction. We reported an exception to the gauche effect due to the enhanced stability observed for the Tg+ conformer. All the structures present the same disposition of the acetamido group, which explains the highly selective binding of N-acetylglucosamine with different amino acid residues. Thus, the comprehensive structural data provided here shall help to shed some light on the biological role of this relevant amino sugar.

Sequential Copper-Catalyzed Amidation and Hydroxylation for Acetaminophen Synthesis

AbstractA sequential Cu-catalyzed amidation and hydroxylation of p-dihalobenzenes is applied to synthesize acetaminophen. This method allows the direct introduction of acetamido and hydroxy groups under acid-free conditions without forming other regioisomers. By using a one-pot process, acetaminophen can be prepared with an overall yield of up to 74%.

Comparative study of experimental and DFT calculations for 3-cinnamoyl 4-hydroxycoumarin derivatives.

Computational research plays an important role in predicting the chemical and physical properties of biologically active compounds important in future structural modifications to improve or modify biological activity. This research focuses on quantum chemical and spectroscopic investigations properties of synthesized 4-hydroxycoumarin derivatives. Quantum chemical calculations were obtained using B3LYP, HF, and M06-2x level methods with the 6-31++G (d,p) basis set. Afterward, IR, 1H, 13C, UV-Visible experimentally parameters were compared with the results obtained using the B3LYP/6-31+G*(d) basis set of the molecules to be able to characterize the structures. Based on the quantum chemical calculations compound with acetamido group on the phenyl ring is the most reactive, and compound with nitro substituent is the least reactive and the the strongest electrophile among tested compounds. With the exception of compounds with dimethylamino group, all other compounds have a pronounced tautomer between OH and C = O group. The calculated and experimental values are in agreement with each other. The molecular structure in the ground state of six 3-cinnamoyl 4-hydroxycoumarin derivatives was optimized using density functional theory. The observed and computed values were compared and it can be concluded that the theoretical results were in good linear agreement with the experimental data.

Characteristic reactivity of 3-acetamido-5-acetylfuran under oxidation conditions

Abstract Chitin is an abundant nitrogen-containing biomass and a major derivative is 3-acetamido-5-acetylfuran (3A5AF). The oxidation of 3A5AF could produce 3-acetamido-5-carboxyfuran (3A5CF), which is a promising monomer for producing nitrogen-containing polymers. However, the conversion of 3A5AF into 3A5CF is actually difficult. The present study clarifies the characteristic reactivity of 3A5AF under typical oxidation reaction conditions. Specifically, corresponding benzene derivatives or acetylfuran are transformed into carboxylic acids, but 3A5AF cannot. Then, density functional theory calculations indicate that 3A5AF facilitates the radical addition reaction on the furan ring instead of the oxidation of the C-acetyl group. In addition to the low aromaticity of furan, the acetamido group stabilizes the radical adduct by orbital interactions. Finally, we provide a potential methodology to decrease the reactivity of the furan ring in 3A5AF.

From Potential Prebiotic Synthons to Useful Chiral Scaffolds: A Synthetic and Structural Reinvestigation of 2-Amino-Aldononitriles.

This paper explores and revisits in detail the formation and characterization of sugar-based aminonitriles, whose ultimate origin can be traced to the interaction of biomolecules with cyanide. Although the synthesis and spectroscopic data of 2-amino-aldononitriles were reported long ago, there are both contradictory and confusing results among the published data. We have now addressed this concern through an exhaustive structural elucidation of acylated 2-amino- and 2-alkyl(aryl)amino-2-deoxyaldonitriles using mass spectrometry and FT-IR, FT-Raman, and NMR spectroscopies. Several structures could be unambiguously determined through single-crystal X-ray diffraction, which allowed us to correct other misassignments. Moreover, this study unveils how steric and electronic effects influence the acylation outcome of the amino, (alkyl, aryl)amino, or acetamido group at C-2. The chirality at the latter, which was assigned tentatively through optical rotation correlation, and hence the preferential threo stereochemistry generated during the cyanohydrin synthesis of 2-amino-2-deoxy aldononitriles have now been established with confidence.

Design and Synthesis of Novel Amino and Acetamidoaurones with Antimicrobial Activities.

The development of new and effective antimicrobial compounds is urgent due to the emergence of resistant bacteria. Natural plant flavonoids are known to be effective molecules, but their activity and selectivity have to be increased. Based on previous aurone potency, we designed new aurone derivatives bearing acetamido and amino groups at the position 5 of the A ring and managing various monosubstitutions at the B ring. A series of 31 new aurone derivatives were first evaluated for their antimicrobial activity with five derivatives being the most active (compounds 10, 12, 15, 16, and 20). The evaluation of their cytotoxicity on human cells and of their therapeutic index (TI) showed that compounds 10 and 20 had the highest TI. Finally, screening against a large panel of pathogens confirmed that compounds 10 and 20 possess large spectrum antimicrobial activity, including on bioweapon BSL3 strains, with MIC values as low as 0.78 µM. These results demonstrate that 5-acetamidoaurones are far more active and safer compared with 5-aminoaurones, and that benzyloxy and isopropyl substitutions at the B ring are the most promising strategy in the exploration of new antimicrobial aurones.

Seafood waste derived Pt/Chitin nanocatalyst for efficient hydrogenation of nitroaromatic compounds

The fabrication of reliable, reusable and efficient catalyst is crucial for the conversion of nitroaromatic compounds into more chemically valuable amine-based molecules. In this study, a series of chitin supported platinum (Pt) catalysts with high catalytic activity, stability, and reusability were developed by using chitin derived from seafood waste as raw materials. The catalytic performance differences among these catalysts activated by different methods were investigated by hydrogenation of nitroaromatic compounds. The results showed that the multilayer hierarchical pore structure and abundance of hydroxyl and acetamido groups in chitin provided ample anchoring sites for Pt nanoparticles (NPs), ensuring the high dispersion of Pt NPs. Moreover, the interconnected channels between chitin nanofibrous microspheres facilitated rapid transport of reaction substrates. The best Pt/Chitin catalyst exhibited excellent catalytic activity and broad substrate applicability in hydrogenation of nitroaromatic compounds. Significantly, even after 20 runs, no discernible deactivation of activity was observed, demonstrating exceptional catalytic reusability. The application of seafood waste-based catalysts is conducive to the development of a green/sustainable society.

Substituent and Solvent Effects on the Spectral Properties of 3-Substituted Derivatives of 4-Hydroxycoumarin

Solvent and substitution effects on the UV/Vis spectroscopic and fluorescence behaviour of seven synthesized 3-substituted 4-hydroxycoumarin derivatives were tested. The tested compounds were dissolved in ethyl acetate, acetonitrile, and dimethyl sulfoxide. Absorption and emission spectra were recorded in the range of 200–800 nm. All tested 4-hydroxycoumarin derivatives showed good absorption in a wide range of 200–550 nm, depending on the properties of the substituents on the benzene ring of the cinnamoyl moiety and the type of solvent. In comparison to the unsubstituted analogue, compounds with an electron-donating group exhibited bathochromically shifted UV/Vis absorption and emission spectra. The highest fluorescence quantum yield was observed for compounds with dimethylamino and acetamido groups as substituents at the benzene ring. Considering that both substitution and solvent affect the absorption and emission spectra of the tested compounds, it can be concluded that judiciously selecting these parameters can improve their absorption and fluorescence properties, making them suitable for various analytical uses.

Boosting 3-acetamido-5-acetylfuran production from N-acetyl-D-glucosamine in γ-valerolactone by a dissolution-dehydration effect

Chitin biorefinery offers a unique opportunity to sustainably produce highly-valued organonitrogen compounds such as the versatile pharmaceutical precursor 3-acetamido-5-acetylfuran (3A5AF), bypassing the Haber process and mitigating the consumption of fossil feedstocks. However, the reported protocols engaged large quantities of toxic organic solvents and required harsh conditions. In this work, a highly efficient catalytic system has been developed in the nontoxic, biobased γ-valerolactone (GVL) solvent under relatively mild conditions. 3A5AF was selectively obtained with an unprecedent yield of 75.3% at 140 °C for 2 h by adding NH4SCN and HCl. The high yielding was exclusively promoted by a dissolution-dehydration effect. Based on the UPLC-TOF-MS and NMR analyses, the presence of NH4SCN has induced a very rapid NAG conversion possibly by coordinating with the acetamido group and the hydroxyl groups, and the 3A5AF product was obtained in a subsequent dehydration pathway from NAG with the Chromogen I and Chromogen III as the intermediates.

Porous chitosan membranes by solvent evaporation technique: evaluation of the biopolymer/acetone ratio and potentiality for the membrane distillation process

ABSTRACT Chitosan is a biopolymer and with proper preparation conditions could be promising for membrane distillation. Based on the current environment-based initiatives, in this work, a chitosan porous membrane was synthesized. The effect of chitosan on the presence of acetone at different concentrations was evaluated and FTIR showed acetamido groups and changes in the degree of deacetylation. The membrane was characterized by water uptake, porosity, and microstructure. It presented moderate hydrophobic behavior and porosities (62%−92%) with slit-like pores. The membrane distillation demonstrated the use of membrane produced with permeate flux (16.07–51.62 kg.m−2.h−1).

Development of chitin nanofiber coatings for prolonging shelf life and inhibiting bacterial growth on fresh cucumbers

The widespread usage of petroleum-based polymers as single-use packaging has had harmful effects on the environment. Herein, we developed sustainable chitin nanofiber (ChNF) coatings that prolong the shelf life of fresh cucumbers and delay the growth of pathogenic bacteria on their surfaces. ChNFs with varying degrees of acetylation were successfully prepared via deacetylation using NaOH with treatment times of 0–480 min and defibrillated using mechanical blending. With longer deacetylation reaction times, more acetamido groups (–NHCOCH3) in chitin molecules were converted to amino groups (–NH2), which imparted antibacterial properties to the ChNFs. The ChNF morphologies were affected by deacetylation reaction time. ChNFs deacetylated for 240 min had an average width of 9.0 nm and lengths of up to several μm, whereas rod-like structured ChNFs with a mean width of 7.3 nm and an average length of 222.3 nm were obtained with the reaction time of 480 min. Furthermore, we demonstrated a standalone ChNF coating to extend the shelf life of cucumbers. In comparison to the rod-like structured ChNFs, the 120 and 240-min deacetylated ChNFs exhibited a fibril-like structure, which considerably retarded the moisture loss of cucumbers and the growth rate of bacteria on their outer surfaces during storage. Cucumbers coated with these 120 and 240-min deacetylated ChNFs demonstrated a lower weight loss rate of ⁓ 3.9% day−1 compared to the uncoated cucumbers, which exhibited a weight loss rate of 4.6% day−1. This protective effect provided by these renewable ChNFs holds promising potential to reduce food waste and the use of petroleum-based packaging materials.

Mapping the Acetylamino and Carboxyl Groups on Glycans by Engineered α-Hemolysin Nanopores.

Glycan is a crucial class of biological macromolecules with important biological functions. Functional groups determine the chemical properties of glycans, which further affect their biological activities. However, the structural complexity of glycans has set a technical hurdle for their direct identification. Nanopores have emerged as highly sensitive biosensors that are capable of detecting and characterizing various analytes. Here, we identified the functional groups on glycans with a designed α-hemolysin nanopore containing arginine mutations (M113R), which is specifically sensitive to glycans with acetamido and carboxyl groups. Molecular dynamics simulations indicated that the acetamido and carboxyl groups of the glycans produce unique electrical signatures by forming polar and electrostatic interactions with the M113R nanopores. Using these electrical features as the fingerprints, we mapped the length of the glycans containing acetamido and carboxyl groups at the monosaccharide, disaccharide, and trisaccharide levels. This proof-of-concept study provides a promising foundation for developing single-molecule glycan fingerprinting libraries and demonstrates the capability of biological nanopores in glycan sequencing.

A Short Review on Biological Activities of Paracetamol Derivatives

Paracetamol reduces body temperature with multiple mechanisms. Paracetamol is chemically 4-hydroxy acetanilide and has a good safety profile. Following its successful use as an over-the-counter antipyretic and analgesic medication, several attempts were made to increase the potency, mask the bitter taste, and decrease the toxicity of this drug by modifications at the phenyl ring, acetamido group, and hydroxyl group. The free hydroxyl group of paracetamols was masked to obtain prodrugs (carbonate prodrugs, ester prodrugs like alanine-prodrug, proline-prodrug, galactosylated prodrug, and mutual prodrugs with other drugs and NSAIDs). Propacetamol is a commercially available prodrug derived from paracetamol that is effective in parenteral form. Paracetamol ester prodrugs with sulfur-containing amino acids such as N-acetyl cysteine, cysteine, and methionine showed low hepatotoxicity compared to the parent drug. In addition, paracetamol derivatives including metal complexes, chalcones, Mannich bases, nucleoside analogs, hybrids with the aryl-imidazolidinyl ring, thymol, and triazole ring displayed diverse activities like antioxidant, anticancer, and antimicrobial activities.

Expanding Chitosan Reticular Chemistry Using Multifunctional and Thermally Stable Phosphorus-Containing Dendrimers

Chitosan is an astonishing building block that is extracted from marine crustacean waste, features randomly distributed amino and acetamido groups in its backbone, and can be handled in different forms, giving rise to an impressive diversity of functional nanomaterials. Hitherto, its reticular chemistry, although mandatory to circumvent its main drawback of instability, has been dominated by the use of glutaraldehyde. Unfortunately, the toxicity and inherent chemistry of the latter narrow further development of such cross-linked materials and constitute an impediment for their massive spreading and real implementation, especially in nanomedicine and related healthcare applications. Prompted by the well-established advantages of dendrimers, more distinctively those containing phosphorus in their skeleton, we herein explore the use of second- and third-generation phosphorus-containing dendrimers as cross-linkers to provide an extended covalent dendritic framework grown inside of the carbohydrate network. The presence of residual amine and aldehyde defects was explored to conjugate other chemicals (viologen-based ionic liquid and aminopropyltriethoxysilane) thereby adding more functional diversity to the assembled framework. We also leveraged on the film-forming ability of chitosan to shape the reticular network as flexible films. Despite the bulkiness of the used phosphorus dendrimers, the film-forming memory of chitosan was preserved, allowing successful preparation of highly functional, transparent, and flexible micrometer-thick bioplastics. The cross-linking seems to delay the half-weight degradation temperature of the plastics, with a significant increase in the char residue and a reduced heat release rate. Ternary objects (Congo red dye and gold nanoparticles) could also be entrapped within the transparent films without leaching or degradation, thereby expanding the usefulness of these transparent coatings as multifunctional sensors, flame retardants, biofoulants, etc.

Multilayer perceptron neural network applied to TG dynamic data of biopolymer chitosan – A robust tool to study the kinetics of solid thermal decomposition

• New artificial neural network to study kinetics of solid thermal decomposition. • MLP neural network applied in TG non-isothermal data to determine kinetic triplet. • Validation of new MLP is made using simulated data with kinetic model combination. • Accurate kinetic study of chitosan thermal decomposition process. • Multi-step reactions are described by combination of kinetic models. Thermogravimetric analysis (TG) was used to investigate the thermal degradation process of chitosan under dynamic condition. A methodology based on multilayer perceptron neural network (MLP) was proposed and allows quantifying the contribution of each kinetic models to better describe experimental data. Artificial neural networks (ANN) have been applied to chemical problems to reproduce experimental data with higher accuracy, acting in this way as a universal approximation method. In this work, the MLP architecture uses the approximation on the integral temperature by Coats and Redefern, isoconversional KAS methodology and integral kinetic models. The neurons in the hidden layer are activated by kinetic models, not only to reproduce the experimental data, but to bring physical information about the thermal process. The MLP validation was carried out using simulated data, the neural network retrieves the mechanism based on the residual error and consider the curve shape. For the chitosan experimental data, the MLP shows the lowest residual error to fit experimental data, which were performed at N 2 atmosphere under four heating rates: 2.5, 5.0, 7.5, and 10 ° C min - 1 . The activation energy was calculated as 98.1 to 183.3 kJ mol - 1 along the conversion degree. This increasing behavior of activation energy is due to initial polymer dehydration, which foments the enhancement of intramolecular interactions between the monomers and also the stronger intermolecular interactions between the interconnected layers of polymeric chains. Due to decomposition of hydroxyl and acetamido groups, the MLP determined contribution of two-dimensional diffusion model (D2) and for the breakdown of the glycosidic bond, MLP determined high contribution of the volume contraction model (R3) followed by surface area contraction model (R2). These results corroborate the expected behavior as solid interconnected material along the energy supply experiment.

Mitigating Ring‐Opening to Develop Stable TEMPO Catholytes for pH‐Neutral All‐Organic Redox Flow Batteries

AbstractRedox‐active organics are highly attractive in aqueous organic redox flow batteries (AORFBs). However, the lack of capacity dense, stable organic catholytes remains a challenge to develop energy‐dense, long cycle‐life AORFBs. Herein, a stable organic catholyte, 4‐[3‐(trimethylammonium)acetylamino]‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl chloride (TMAAcNHTEMPO) is developed through rational molecular engineering using connective acetamido and trimethylammonium groups. Paired with bis‐(trimethylammonium) propyl viologen tetrachloride anolyte, stable AORFBs (up to 1500 cycles) with a low capacity fade rate of ca. 0.0144% h−1 are achieved. Experimental characterizations and theoretical simulations revealed that TMAAcNH‐TEMPO is largely stabilized by the reduced reactivity of the nitroxyl radical moiety that mitigates a ring‐opening side reaction.

Crystal structure and Hirshfeld surface analysis of 2-chloro-N-(4-meth-oxy-phen-yl)acetamide.

In the title mol-ecule, C9H10ClNO2, the meth-oxy group lies very close to the plane of the phenyl ring while the acetamido group is twisted out of this plane by 28.87 (5)°. In the crystal, a three-dimensional structure is generated by N-H⋯O, C-H⋯O and C-H⋯Cl hydrogen bonds plus C-H⋯π(ring) inter-actions. A Hirshfeld surface analysis of the inter-molecular inter-actions was performed and indicated that C⋯H/H⋯C inter-actions make the largest contribution to the surface area (33.4%).

N-(4-Meth-oxy-2-nitro-phen-yl)acetamide.

In the title compound, C9H10N2O4, the three substituents vary in the degree of lack of planarity with the central phenyl ring. The meth-oxy group is nearest to being coplanar, with a C-C-O-C torsion angle of 6.1 (5)°. The nitro group is less coplanar, with a 12.8 (5)° twist about the C-N bond and the acetamido group is considerably less coplanar with the central ring, having a 25.4 (5)° twist about the C-N bond to the ring. The NH group forms an intra-molecular N-H⋯O hydrogen bond to a nitro-group O atom.

Acetamido-functionalized hyper-crosslinked polymers for efficient removal of phenol in aqueous solution

In recent years, functionalized hyper-crosslinked polymers (HCPs) have received increasing attention due to their high Brunauer − Emmett − Teller (BET) surface area (SBET), adjustable porosity and diversified functionality. Herein, the acetamido-functionalized HCPs namely PS-PDAT-FDA(SnCl4) were synthesized by two successive Friedel − Crafts reactions and the resultant polymers offered high SBET (756 m2/g), abundant N (4.6%) and O content (9.5%), and unique hierarchical porosity. The adsorption experiments indicated that the fabricated HCPs had a good adsorption of phenol with the predicted maximum capacity (qmax) of 214.5 mg/g. Increasing the Na2SO4 concentration slightly enhanced the adsorption, about 90 min was needed for the adsorption reaching the equilibrium, and the adsorption in tap water was also excellent. The adsorption mechanism revealed the uploaded C = O functionalities of the acetamido groups made a great positive contribution to the enhanced adsorption and strong hydrogen bonding between the C = O functionalities of the polymers and the phenolic hydroxyl groups of phenol was the main driving force.

Chitin Deacetylase, a Novel Target for the Design of Agricultural Fungicides.

Fungicide resistance is a serious problem for agriculture. This is particularly apparent in the case of powdery mildew fungi. Therefore, there is an urgent need to develop new agrochemicals. Chitin is a well-known elicitor of plant immunity, and fungal pathogens have evolved strategies to overcome its detection. Among these strategies, chitin deacetylase (CDA) is responsible for modifying immunogenic chitooligomers and hydrolysing the acetamido group in the N-acetylglucosamine units to avoid recognition. In this work, we tested the hypothesis that CDA can be an appropriate target for antifungals using the cucurbit powdery mildew pathogen Podosphaera xanthii. According to our hypothesis, RNAi silencing of PxCDA resulted in a dramatic reduction in fungal growth that was linked to a rapid elicitation of chitin-triggered immunity. Similar results were obtained with treatments with carboxylic acids such as EDTA, a well-known CDA inhibitor. The disease-suppression activity of EDTA was not associated with its chelating activity since other chelating agents did not suppress disease. The binding of EDTA to CDA was confirmed by molecular docking studies. Furthermore, EDTA also suppressed green and grey mould-causing pathogens applied to oranges and strawberries, respectively. Our results conclusively show that CDA is a promising target for control of phytopathogenic fungi and that EDTA could be a starting point for fungicide design.