Solvent free, N,N′-carbonyldiimidazole (CDI) mediated amidation

Hexylsilane-mediated direct amidation of amino acids with a catalytic amount of 1,2,4-triazole

In this study, we report amino acid amidation using hexylsilane and a catalytic amount of 1,2,4-triazole. The conventional protection/deprotection method for the α-amino group of amino acids is not required. The corresponding α-amino amides were obtained in moderate to good yields with low to no racemization.

Water-soluble fluorine-functionalized chitooligosaccharide derivatives: Synthesis, characterization and antimicrobial activity

In this work, a series of water-soluble fluorine-functionalized chitooligosaccharide derivatives were synthesized by conjugating nicotinic acid to chitooligosaccharide via nicotinylation reaction, followed by nucleophilic reaction with ethyl bromide, benzyl bromide and fluorobenzyl bromides. Synthesized derivatives were identified structurally by Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance. In addition, the antibacterial activities of chitooligosaccharide derivatives against several disease-causing bacteria were assessed by the broth dilution method and Kirby-Bauer method, the mycelium growth rate method was used to assessing the antifungal properties of samples against three plant-threatening fungi. Among the chitooligosaccharide derivatives, those containing benzyl or fluorobenzyl exhibited noteworthy antimicrobial activity. Specifically, the chitooligosaccharide derivative containing 2,3,4-trifluorobenzyl displayed remarkable antimicrobial activity, with an inhibition index of 84.35% against Botryis cinerea at a concentration of 1.0 mg/mL. Additionally, its MIC value against Staphylococcus aureus was found to be 0.03125 mg/mL, while the MBC value was determined to be 0.0625 mg/mL. The findings of the study revealed that the incorporation of pyridinium cations and fluorine into the chitooligosaccharide backbone may play a critical role in strengthening its ability to combat harmful microorganisms. Furthermore, the cytotoxicities of chitooligosaccharide derivatives against Huvec cells were evaluated through MTT assay, and all samples were not toxic. As a consequence, the water-soluble fluorine-functionalized chitooligosaccharide derivatives possessed rapid microbicidal properties and good biocompatibility, which provided promising prospects for the development of a more effective and environmentally friendly antimicrobial agent.

Synthesis of Dolutegravir Exploiting Continuous Flow Chemistry

An efficient continuous flow process for the synthesis of dolutegravir, an active pharmaceutical ingredient (API) for HIV treatment, was investigated. The synthetic procedure starts from a readily available benzyl-protected pyran via six chemical transformations using continuous flow reactors. The significant advantage of this flow process includes the reduction of the overall reaction time from 34.5 h in batch to 14.5 min. The overall yield of each reaction step improved dramatically upon flow optimization. Another key feature of this synthesis is telescoping multiple steps.

Cationic Chitooligosaccharide Derivatives Bearing Pyridinium and Trialkyl Ammonium: Preparation, Characterization and Antimicrobial Activities

In this study, chitooligosaccharide-niacin acid conjugate was designed and synthesized through the reaction of chitooligosaccharide and nicotinic acid with the aid of N,N'-carbonyldiimidazole. Its cationic derivatives were prepared by the further nucleophilic substitution reaction between the chitooligosaccharide-niacin acid conjugate and bromopropyl trialkyl ammonium bromide with different alkyl chain lengths. The specific structural characterization of all derivatives was identified using Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR), and the degree of substitution was obtained using the integral area ratio of the hydrogen signals. Specifically, the antibacterial activities against Escherichia coli, Staphylococcus aureus, Pseudoalteromonas citrea and Vibrio harveyi were evaluated using broth dilution methods. In addition, their antifungal activities, including Botrytis cinerea, Glomerella cingulate and Fusarium oxysporum f. sp. cubense were assayed in vitro using the mycelium growth rate method. Experimental data proved that the samples showed antibacterial activity against four pathogenic bacteria (MIC = 1-0.125 mg/mL, MBC = 8-0.5 mg/mL) and enhanced antifungal activity (50.30-68.48% at 1.0 mg/mL) against Botrytis cinerea. In particular, of all chitooligosaccharide derivatives, the chitooligosaccharide derivative containing pyridinium and tri-n-butylamine showed the strongest antibacterial capacity against all of the test pathogenic bacteria; the MIC against Vibrio harveyi was 0.125 mg/mL and the MBC was 1 mg/mL. The experimental results above showed that the introduction of pyridinium salt and quaternary ammonium salt bearing trialkyl enhanced the antimicrobial activity. In addition, the cytotoxicity against L929 cells of the chitooligosaccharide derivatives was evaluated, and the compounds exhibited slight cytotoxicity. Specifically, the cell viability was greater than 91.80% at all test concentrations. The results suggested that the cationic chitooligosaccharide derivatives bearing pyridinium and trialkyl ammonium possessed better antimicrobial activity than pure chitooligosaccharide, indicating their potential as antimicrobial agents in food, medicine, cosmetics and other fields.

Coupling of 3-Aminopropyl Sulfonic Acid to Cellulose Nanofibers for Efficient Removal of Cationic Dyes

A novel anionic nanostructured cellulose derivate was prepared through the coupling of TEMPO-oxidized cellulose nanofibers with 3-aminopropyl sulfonic acid (3-APSA). 3-APSA grafting was variously investigated by FT-IR spectroscopy and transmission electron microscopy (TEM) analysis, confirming a high reaction degree. The surface morphology investigated via scanning electron microscopy (SEM) revealed a more uniform organization of the nanofibers after the 3-APSA coupling, with improvements in terms of fiber packing and pore interconnectivity. This peculiar morphology contributes to improving methylene blue (MB) adsorption and removal efficiency at different operating conditions (pH, initial time, and initial concentration). The results indicated a maximum adsorption capacity of 526 mg/g in the case of 3-APSA grafted nanofibers, over 30% more than that of non-grafted ones (370 mg/g), which confirm a relevant effect of chemical modification on the adsorbent properties of cellulose nanofibers. The adsorption kinetics and isotherms of the current adsorbents match with the pseudo-second-order kinetic and Langmuir isotherm models. This study suggests the use of chemical grafting via 3-APSA is a reliable and facile post-treatment to design bio-sustainable and reusable nanofibers to be used as high-performance adsorbent materials in water pollutant remediation.

Green solvents for the formation of amide linkages

The formation of the amide bond is among the most commonly performed transformations in the pharmaceutical industry and the wider chemical industry. The current methods for its installation in organic compounds frequently rely on the use of large amounts of organic solvents, mainly N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dichloromethane (DCM), which have been associated with adverse environmental and health concerns over the last decades. This fact led academia and industry to make significant efforts toward the development of synthetic routes with the aim to avoid, reduce or replace the use of hazardous solvents. The present review fits into this framework and discusses the literature existing over the past ten years on strategies for reducing and replacing hazardous solvents, focusing on the use of biobased and neoteric solvents, such as ionic liquids and deep eutectic solvents (ILs and DESs, respectively), and on the reaction media that proved to be greener alternatives for amide bond formation.

Non-isocyanate Polyurethanes from 1,1'-Carbonyldiimidazole: A Polycondensation Approach

1,1'-Carbonyldiimidazole (CDI) provides a platform to generate high molecular weight polyurethanes from industrially relevant diols and diamines. CDI, which is described in the literature for its use in amidation and functionalization reactions, enables the production of well-defined and stable polyurethane precursors, thus eliminating the need for isocyanates. Herein, the functionalization of 1,4-butanediol with CDI yields an electrophilic biscarbamate, bis-carbonylimidazolide (BCI), which is suitable for further step-growth polymerization in the presence of amines. Elevated reaction temperatures enable the solvent-, catalyst-, and isocyanate-free polycondensation reaction between the BCI monomer and various diamines. The thermoplastic polyurethanes produced from this reaction demonstrate high thermal stability, tunable glass transition temperatures based on incorporation of flexible polyether segments, and mechanically ductile thin films. CDI functionalized diols will allow the preparation of diverse polyurethanes without the use of isocyanate-containing monomers.

Synthesis of amides and esters containing furan rings under microwave-assisted conditions

In this work, we present a novel method for the synthesis of ester and amide derivatives containing furan rings (furfural derivatives) under mild synthetic conditions supported by microwave radiation. N-(Furan-2-ylmethyl)furan-2-carboxamide and furan-2-ylmethyl furan-2-carboxylate were produced using 2-furoic acid, furfurylamine, and furfuryl alcohol. The reactions were carried out in a microwave reactor in the presence of effective coupling reagents: DMT/NMM/TsO− or EDC. The reaction time, the solvent, and the amounts of the substrates were optimized. After crystallization or flash chromatography, the final compounds were isolated with good or very good yields. Our method allows for the synthesis of N-blocked amides using N-blocked amino acids (Boc, Cbz, Fmoc) and amine. As well as compounds with a monoamide and ester moiety, products with diamides and diester bonds (N,N-bis(furan-2-ylmethyl)furan-2,5-dicarboxamide, bis(furan-2-ylmethyl) furan-2,5-dicarboxylate, and furan-3,4-diylbis(methylene) bis(furan-2-carboxylate)) were synthesized with moderate yields in the presence of DMT/NMM/TsO– or EDC, using 2,5-furandicarboxylic acid and 3,4-bis(hydroxymethyl)furan as substrates.

Catalytic Room-Temperature C-N Coupling of Amides and Isocyanates by Using Mechanochemistry

A mechanochemical route is developed for room-temperature and solvent-free derivatization of different types of amides into carbamoyl isatins (up to 96 % conversion or yield), benzamides (up to 81 % yield), and imides (up to 92 % yield). In solution, this copper-catalyzed coupling either does not take place or requires high temperatures at which it may also be competing with alternative thermal reactivity, highlighting the beneficial role of mechanochemistry for this reaction. Such behavior resembles the previously investigated coupling with sulfonamide substrates, suggesting that this type of C-N coupling is an example of a mechanochemically favored reaction, for which mechanochemistry appears to be a favored environment over solution.

Stereospecific Cross-Coupling Reactions Provide Conformationally-Biased Arylalkanes with Anti-Leukemia Activity

A focused small library of carbamates and alcohols was prepared employing stereospecific Kumada-ring opening reactions of tetrahydropyrans. The core framework of the library members is acyclic and incorporates 1,3-substituents, to provide a conformational bias in avoiding syn-pentane interactions. A new compound with micromolar activity against MOLT-4, CCRF-CEM, and HL-60(TB) leukemia cell lines was identified from this series.

Microwave-assisted synthesis, biological evaluation and molecular docking studies of new coumarin-based 1,2,3-triazoles

Coumarin-based 1,4-disubstituted 1,2,3-triazole derivatives were synthesized using a highly efficient, eco-friendly protocol via a copper(i)-catalyzed click reaction between various substituted arylazides and terminal alkynes.

Synthetic Strategies for Dinucleotides Synthesis

Dinucleoside 5′,5′-polyphosphates (DNPs) are endogenous substances that play important intra- and extracellular roles in various biological processes, such as cell proliferation, regulation of enzymes, neurotransmission, platelet disaggregation and modulation of vascular tone. Various methodologies have been developed over the past fifty years to access these compounds, involving enzymatic processes or chemical procedures based either on P(III) or P(V) chemistry. Both solution-phase and solid-support strategies have been developed and are reported here. Recently, green chemistry approaches have emerged, offering attracting alternatives. This review outlines the main synthetic pathways for the preparation of dinucleoside 5′,5′-polyphosphates, focusing on pharmacologically relevant compounds, and highlighting recent advances.

Green Synthesis of Spiropyranone 3-Aryl-4-Methylcoumarin Derivatives using Carbonyldiimidazole

A series of spiropyranone 3-aryl-4-methylcoumarin derivatives have been synthesized from monospiro-2-hydroxy acetophenone in a novel and efficient green method using imidazolyl intermediates and inorganic base. Imidazolyl intermediates were in turn generated by grinding the respective phenylacetic acid along with carbonyldiimidazole (CDI). Similarly, monospiro-2-hydroxy acetophenone derivatives were prepared selectively by avoiding formation of bis derivatives following literature procedure. The titled compounds were purified by preparative TLC technique and were characterized by IR, 1H NMR, 13C NMR as well as mass spectral methods

N-alkylimidazolium Salts Functionalized with p-Coumaric and Cinnamic Acid: A Study of Their Antimicrobial and Antibiofilm Effects

The bacterial resistance to antibiotics has compromised the therapies used for bacterial infections. Nowadays, many strategies are being carried out to address this problem. Among them, the use of natural compounds like cinnamic and p-coumaric acids stands out. Nevertheless, their utilization is limited because of their unfavorable physicochemical properties. Due to the lack of new therapeutic alternatives for bacterial infections, novel strategies have emerged, such as the use of ionic liquids; given that they can show a broad spectrum of antibacterial activity, this is why we herein report the antibacterial and antibiofilm activity of a series of N-alkylimidazolium salts functionalized with p-coumaric and cinnamic acids. The results from this study showed better antibacterial activity against Gram-positive bacteria, with a predominance of the salts derived from coumaric acid and a correlation with the chain length. Additionally, a lower efficacy was observed in the inhibition of biofilm formation, highlighting the antibiofilm activity against Staphylococcus aureus, which decreased the production of the biofilm by 52% over the control. In conclusion, we suggest that the salts derived from p-coumaric acid are good alternatives as antibacterial compounds. Meanwhile, the salt derived from cinnamic acid could be a good alternative as an antibiofilm compound.

(Ar-tpy)RuII(ACN)3: A Water-Soluble Catalyst for Aldehyde Amidation, Olefin Oxo-Scissoring, and Alkyne Oxygenation

The synthetic chemists always look for developing new catalysts, sustainable catalysis, and their applications in various organic transformations. Herein, we report a new class of water-soluble complexes, (Ar-tpy)Ru^II(ACN)₃, utilizing designed terpyridines possessing electron-donating and -withdrawing aromatic residues for tuning the catalytic activity of the Ru(II) complex. These complexes displayed excellent catalytic activity for several oxidative organic transformations including late-stage C-H functionalization of aldehydes with NH₂OR to valuable primary amides in nonconventional aqueous media with excellent yield. Its diverse catalytic power was established for direct oxo-scissoring of a wide range of alkenes to furnish aldehydes and/or ketones in high yield using a low catalyst loading in the water. Its smart catalytic activity under mild conditions was validated for dioxygenation of alkynes to highly demanding labile synthons, 1,2-diketones, and/or acids. This general and sustainable catalysis was successfully employed on sugar-based substrates to obtain the chiral amides, aldehydes, and labile 1,2-diketones. The catalyst is recovered and reused with a moderate turnover. The proposed mechanistic pathway is supported by isolation of the intermediates and their characterization. This multifaceted sustainable catalysis is a unique tool, especially for late-stage functionalization, to furnish the targeted compounds through frequently used amidation and oxygenation processes in the academia and industry.

Straightforward Ball-Milling Access to Dinucleoside 5',5'-Polyphosphates via Phosphorimidazolide Intermediates

A solvent-assisted mechanochemical approach to access symmetrical and mixed dinucleoside 5,5'-polyphosphates is reported. Under ball-milling conditions, nucleoside 5'-monophosphates were quantitatively activated using 1,1'-carbonyldiimidazole, forming their phosphorimidazolide derivatives. The addition of a nucleoside 5'-mono-, di- or triphosphate directly led to the formation of the corresponding dinucleotides. Benefits of the reported one-pot method include the use of unprotected nucleotides in their sodium or acid form, activation by the eco-friendly 1,1'-carbonyldiimidazole, non-dry conditions, short reaction time, high conversion rates, and easy setup and purification. This work offers new perspectives for the synthesis of nucleotide conjugates and analogues, combining the phosphorimidazolide approach and milling conditions.

Synthesis of Electroneutralized Amphiphilic Copolymers with Peptide Dendrons for Intramuscular Gene Delivery

Intramuscular gene delivery materials are of great importance in plasmid-based gene therapy system, but there is limited information so far on how to design and synthesize them. A previous study showed that the peptide dendron-based triblock copolymer with its components arranged in a reversed biomembrane architecture could significantly increase intramuscular gene delivery and expression. Herein, we wonder whether copolymers with biomembrane-mimicking arrangement may have similar function on intramuscular gene delivery. Meanwhile, it is of great significance to uncover the influence of electric charge and molecular structure on the function of the copolymers. To address the issues, amphiphilic triblock copolymers arranged in hydrophilic-hydrophobic-hydrophilic structure were constructed despite the paradoxical characteristics and difficulties in synthesizing such hydrophilic but electroneutral molecules. The as-prepared two copolymers, dendronG2(l-lysine-OH)-poly propylene glycol2k(PPG2k)-dendronG2(l-lysine-OH) (rL2PL2) and dendronG3(l-lysine-OH)-PPG2k-dendronG3(l-lysine-OH) (rL3PL3), were in similar structure but had different hydrophilic components and surface charges, thus leading to different capabilities in gene delivery and expression in skeletal muscle. rL2PL2 was more efficient than Pluronic L64 and rL3PL3 when mediating luciferase, β-galactosidase, and fluorescent protein expressions. Furthermore, rL2PL2-mediated growth-hormone-releasing hormone expression could significantly induce mouse body weight increase in the first 21 days after injection. In addition, both rL2PL2 and rL3PL3 showed good in vivo biosafety in local and systemic administration. Altogether, rL2PL2-mediated gene expression in skeletal muscle exhibited applicable potential for gene therapy. The study revealed that the molecular structure and electric charge were critical factors governing the function of the copolymers for intramuscular gene delivery. It can be concluded that, combined with the previous study, both structural arrangements either reverse or similar to the biomembrane are effective in designing such copolymers. It also provides an innovative way in designing and synthesizing new electroneutralized triblock copolymers, which could be used safely and efficiently for intramuscular gene delivery.

Heterobimetallic dinuclear lanthanide alkoxide complexes as acid–base bifunctional catalysts for synthesis of carbamates under solvent-free conditions

Heterobimetallic dinuclear lanthanide alkoxide complexes Ln₂Na₈(OCH₂CH₂NMe₂)₁₂(OH)₂ [Ln: I (Nd), II (Sm), III (Yb) and IV (Y)] were used as efficient acid–base bifunctional catalysts for the synthesis of carbamates and the N-Boc protection of amines.

[Development of targeted drug delivery system: synthesis of conjugates of address fragment (RA-COOH) with ligand (R-NH2)]

One of the main ways to increase the effectiveness of well-known medical formulations well-established in clinical medicine - development of delivery systems using new technological approaches and nanomaterials. Currently, much attention is given to targeted delivery systems. At the same time drug carrier has in addition to medication the so-called vector/address with a high affinity for binding to specific receptors on cells/tissue target. In this paper it is described the method for producing of address conjugates to over-expressed receptors on the tumor cells. As address fragment it was folic acid and as a linker was dodecylamine, causing inclusion the conjugate into lipid nanoparticles.

Pharmacological agents and transport nanosystems based on plant phospholipids

A new generation of plant phosphatidylcholine (PC)-based pharmacological agents has been developed under academician A.I. Archakov leadership at the Institute of Biomedical Chemistry (IBMC). For their production a unique technology allowing to obtain dry lyophilized phospholipid nanoparticles of 30 nm was elaborated. The successful practical application of PC nanoparticles as a drug agent may be illustrated by Phosphogliv (oral and injection formulations). Being developed at IBMC for the treatment of liver diseases, including viral hepatitis, Phosphogliv (currently marketed by the “Pharmstandard” company) is approved for clinical application in 2000, and is widely used in medical practice. Based on the developed and scaled in IBMC technology of prerparation of ultra small size phospholipid nanoparticles without the use of detergents/surfactants and stabilizers another drug preparation, Phospholipovit, exhibiting pronounced hypolipidemic properties has been obtained. Recently completed preclinical studies have shown that PC nanoparticles of 20-30 nm activate reverse cholesterol transport (RCT) and in this context it is more active than well known foreign preparation Essentiale. Phospholipovit is now at the stage of clinical trials (phase 1 completed). PC was also used as a basis for the development of a transport nanosystem with a particles size of 20-25 nm in diameter and incorporation of various drug substances from various therapeutic groups. Using several drugs substances as an example, increased bioavailability and specific activity were demonstrated for the formulations equipped with such transport nanosystem. Formulations equipped with the transport nanosystems have been developed for such pharmacological agents as doxorubicin, rifampin, budesonide, chlorin E6, prednisone, and others.

Solventless mechanosynthesis of N-protected amino esters

Mechanochemical derivatizations of N- or C-protected amino acids were performed in a ball mill under solvent-free conditions. A vibrational ball mill was used for the preparation of N-protected α- and β-amino esters starting from the corresponding N-unmasked precursors via a carbamoylation reaction in the presence of di-tert-butyl dicarbonate (Boc2O), benzyl chloroformate (Z-Cl) or 9-fluorenylmethoxycarbonyl chloroformate (Fmoc-Cl). A planetary ball mill proved to be more suitable for the synthesis of amino esters from N-protected amino acids via a one-pot activation/esterification reaction in the presence of various dialkyl dicarbonates or chloroformates. The spot-to-spot reactions were straightforward, leading to the final products in reduced reaction times with improved yields and simplified work-up procedures.

Mechanosynthesis of amides in the total absence of organic solvent from reaction to product recovery

The synthesis of various amides has been realised avoiding the use of any organic solvent from activation of carboxylic acids with CDI to isolation of the amides. Mechanochemistry was the key point of the process allowing rapid formation of the amide bond and efficient water-based purification of the final products.

Unprecedented "In Water" imidazole carbonylation: paradigm shift for preparation of urea and carbamate

The first "In Water" imidazolecarbonylation of amine is described. A one pot reaction of carbonylimidazolide in water with a nucleophile provides an efficient and general method for the preparation of urea, carbamates and thiocarbamates. Use of an anhydrous solvent and an inert atmosphere could be avoided. Product precipitate out from the reaction mixture and can be obtained in high purity by filtration, resulting in a simple and scalable method.