Novel carbohydrate-based chiral ammonium ionic liquids derived from isomannide

Investigations on the Synthesis of Chiral Ionic-Liquid-Supported Ligands and Corresponding Transition-Metal Catalysts: Strategy and Experimental Schemes

Ionic liquids have been utilized in numerous significant applications within the field of chemistry, particularly in organic chemistry, due to their unique physical and chemical properties. In the realm of asymmetric transition-metal-catalyzed transformations, chiral ionic-liquid-supported ligands and their corresponding transition-metal complexes have facilitated these processes in unconventional solvents, especially ionic liquids and water. These innovative reaction systems enable the recycling of transition-metal catalysts while producing optically active organic molecules with comparable or even higher levels of chemo-, regio-, and stereoselectivity compared to their parent catalysts. In this short review, we aim to provide an overview of the structures of chiral ionic-liquid-supported ligands and the synthetic pathways for these ligands and catalysts. Various synthetic methodologies are demonstrated based on the conceptual frameworks of diverse chiral ionic-liquid-supported ligands. We systematically present the structures and comprehensive synthetic pathways of the chiral ionic-liquid-supported ligands and the typical corresponding transition-metal complexes that have been readily applied to asymmetric processes, categorized by their parent ligand framework. Notably, the crucial experimental procedures are delineated in exhaustive detail, with the objective of enhancing comprehension of the pivotal aspects involved in constructing chiral ionic-liquid-tagged ligands and compounds for both scholars and readers. Considering the current limitations of such ligands and catalysts, we conclude with remarks on several potential research directions for future breakthroughs in the synthesis and application of these intriguing ligands.

Applications of Ionic Liquids in Carboxylic Acids Separation

Ionic liquids (ILs) are considered a green viable organic solvent substitute for use in the extraction and purification of biosynthetic products (derived from biomass-solid/liquid extraction, or obtained through fermentation-liquid/liquid extraction). In this review, we analyzed the ionic liquids (greener alternative for volatile organic media in chemical separation processes) as solvents for extraction (physical and reactive) and pertraction (extraction and transport through liquid membranes) in the downstream part of organic acids production, focusing on current advances and future trends of ILs in the fields of promoting environmentally friendly products separation.

Antimicrobial, Cytotoxic and Mutagenic Activity of Gemini QAS Derivatives of 1,4:3,6-Dianhydro-l-iditol

A series of quaternary diammonium salts derivatives of 1,4:3,6-dianhydro-l-iditol were synthesized, using isommanide (1,4:3,6-dianhydro-d-mannitol) as a starting material. Both aromatic (pyridine, 4-(N,N-dimethylamino)pyridine (DMAP), (3-carboxamide)pyridine; N-methylimidazole) and aliphatic (trimethylamine, N,N-dimethylhexylamine, N,N-dimethyloctylamine, N,N-dimethyldecylamine) amines were used, giving eight gemini quaternary ammonium salts (QAS). All salts were tested for their antimicrobial activity against yeasts, Candida albicans and Candida glabrata, as well as bacterial Staphylococcus aureus and Escherichia coli reference strains. Moreover, antibacterial activity against 20 isolates of S. aureus collected from patients with skin and soft tissue infections (n = 8) and strains derived from subclinical bovine mastitis milk samples (n = 12) were evaluated. Two QAS with octyl and decyl residues exhibited antimicrobial activity, whereas those with two decyl residues proved to be the most active against the tested pathogens, with MIC of 16-32, 32, and 8 µg/mL for yeast, E. coli, and S. aureus reference and clinical strains, respectively. Only QAS with decyl residues proved to be cytotoxic in MTT assay against human keratinocytes (HaCaT), IC₅₀ 12.8 ± 1.2 μg/mL. Ames test was used to assess the mutagenic potential of QAS, and none of them showed mutagenic activity in the concentration range 4-2000 µg/plate.

Ionic Liquid-Based Materials for Biomedical Applications

Ionic liquids (ILs) have been extensively explored and implemented in different areas, ranging from sensors and actuators to the biomedical field. The increasing attention devoted to ILs centers on their unique properties and possible combination of different cations and anions, allowing the development of materials with specific functionalities and requirements for applications. Particularly for biomedical applications, ILs have been used for biomaterials preparation, improving dissolution and processability, and have been combined with natural and synthetic polymer matrixes to develop IL-polymer hybrid materials to be employed in different fields of the biomedical area. This review focus on recent advances concerning the role of ILs in the development of biomaterials and their combination with natural and synthetic polymers for different biomedical areas, including drug delivery, cancer therapy, tissue engineering, antimicrobial and antifungal agents, and biosensing.

Insights into the Properties and Potential Applications of Renewable Carbohydrate-Based Ionic Liquids: A Review

Carbohydrate-derived ionic liquids have been explored as bio-alternatives to conventional ionic liquids for over a decade. Since their discovery, significant progress has been made regarding synthetic methods, understanding their environmental effect, and developing perspectives on their potential applications. This review discusses the relationships between the structural properties of carbohydrate ionic liquids and their thermal, toxicological, and biodegradability characteristics in terms of guiding future designs of sugar-rich systems for targeted applications. The synthetic strategies related to carbohydrate-based ionic liquids, the most recent relevant advances, and several perspectives for possible applications spanning catalysis, biomedicine, ecology, biomass, and energy conversion are presented herein.

Sustainable Battery Materials from Biomass

Sustainable sources of energy have been identified as a possible way out of today's oil dependency and are being rapidly developed. In contrast, storage of energy to a large extent still relies on heavy metals in batteries. Especially when built from biomass-derived organics, organic batteries are promising alternatives and pave the way towards truly sustainable energy storage. First described in 2008, research on biomass-derived electrodes has been taken up by a multitude of researchers worldwide. Nowadays, in principle, electrodes in batteries could be composed of all kinds of carbonized and noncarbonized biomass: On one hand, all kinds of (waste) biomass may be carbonized and used in anodes of lithium- or sodium-ion batteries, cathodes in metal-sulfur or metal-oxygen batteries, or as conductive additives. On the other hand, a plethora of biomolecules, such as quinones, flavins, or carboxylates, contain redox-active groups that can be used as redox-active components in electrodes with very little chemical modification. Biomass-based binders can replace toxic halogenated commercial binders to enable a truly sustainable future of energy storage devices. Besides the electrodes, electrolytes and separators may also be synthesized from biomass. In this Review, recent research progress in this rapidly emerging field is summarized with a focus on potentially fully biowaste-derived batteries.

Synthesis of novel carbohydrate based pyridinium ionic liquids and cytotoxicity of ionic liquids for mammalian cells

The large pool of naturally occurring carbohydrates with their diversity in chirality and structure led to the idea of a systematic investigation of carbohydrate based ILs. To this end, we investigated the influence of different ether groups, mainly methyl or ethyl ether, on the secondary OH groups as well as different configurations on physical properties such as melting point, thermostability and especially the influence on cell toxicity. For this investigation we chose α- and β-methyl-, β-allyl- and β-phenyl d-glucopyranose as well as four 1-deoxy-pentoses. In order to be able to classify the results, more ionic liquids with different structural motives were examined for cytotoxicity. Here, we present data that confirm the biocompatibility of such ILs consisting of naturally occurring molecules or their derivatives. The synthesized carbohydrate based ILs were tested for their suitability as additives in coatings for medical applications such as drug-eluting balloons.

Biocompatible ionic liquids: fundamental behaviours and applications

The bio- and eco-friendly nature of biocompatible ionic liquids contributes to their widespread use in a wide range of fields.

Supramolecular interaction of non-racemic benzimidazolium based ion pairs with chiral substrates

A series of novel benzimidazolium-based non-racemic ionic liquids (ILs) was synthesized from low-cost chiral terpenoid alcohols and fully characterized by the use of a wide variety of techniques, such as DSC, ESI-MS, ATR FT-IR, polarimetry as well as 1H and 13C NMR spectroscopy. The ILs were investigated as chiral shift agents for the chiral recognition of racemic mixtures of Mosher's acid potassium salt by 19F NMR spectroscopy, leading to high splitting values of the CF3 signal. Supramolecular interactions between salt and H-C2 of chiral benzimidazolium cation are responsible for the chiral recognition, as was demonstrated by experimental evidences. Indeed, the enantiomeric excess value of enantioenriched substrates depends mainly on the strength of the contact ion pairs.

1-(+)-Dehydroabietylimidazolium Salts as Enantiomer Discriminators for NMR Spectroscopy

Nine new (+)-dehydroabietylimidazolium salts were synthesised and studied as chiral solvating agents for several different racemic aromatic and non-aromatic carboxylate salts. These cationic chiral solvating agents resolve racemic ionic analytes better than non-ionic ones. Bis(dehydroabietylimidazolium) bis(trifluoromethanesulfonimide) gave the best discrimination for the enantiomers of carboxylate salts. Its resolution behaviour was studied by an NMR titration experiment, which indicated 1 : 1 complexation with the racemic analyte. The dehydroabietylimidazolium salts were also useful in enantiomeric excess (ee) determinations, and for the recognition of chirality of racemic aromatic and non-aromatic α-substituted carboxylic acids.

Suitability of bio-based ionic liquids for the extraction and purification of IgG antibodies

In the past decade, remarkable advances in the production and use of antibodies as therapeutic drugs and in research/diagnostic fields have led to their recognition as value-added proteins. These biopharmaceuticals have become increasingly important, reinforcing the current demand for the development of more benign, scalable and cost-effective techniques for their purification. Typical polymer-polymer and polymer-salt aqueous biphasic systems (ABS) have been studied for such a goal; yet, the limited polarity range of the coexisting phases and their low selective nature still are their major drawbacks. To overcome this limitation, in this work, ABS formed by bio-based ionic liquids (ILs) and biocompatible polymers were investigated. Bio-based ILs composed of ions derived from natural sources, namely composed of the cholinium cation and anions derived from plants natural acids, have been designed, synthesized, characterized and used for the creation of ABS with polypropyleneglycol (PPG 400). The respective ternary phase diagrams were initially determined at 25 °C to infer on mixture compositions required to form aqueous systems of two phases, further applied in the extraction of pure immunoglobulin G (IgG) to identify the most promising bio-based ILs, and finally employed in the purification of IgG from complex and real matrices of rabbit serum. Remarkably, the complete extraction of IgG to the IL-rich phase was achieved in a single-step. With pure IgG a recovery yield of 100% was obtained, while with rabbit serum this value slightly decreased to ca. 85%. Nevertheless, a 58% enhancement in the IgG purity was achieved when compared with its purity in serum samples. The stability of IgG before and after extraction was also evaluated by size exclusion high-performance liquid chromatography (SE-HPLC), sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared spectroscopy (FTIR). In most ABS formed by bio-based ILs, IgG retained its native structure, without degradation or denaturation effects, supporting thus their potential as remarkable platforms for the purification of high-cost biopharmaceuticals.

A remarkable chiral recognition of racemic Mosher's acid salt by naturally derived chiral ionic liquids using 19F NMR spectroscopy

A new class of d-xylose derived imidazolium-based chiral ionic liquids were designed and synthesized via simple tuning approaches.

Herbicidal ionic liquids derived from renewable sources

A new family of herbicidal ionic liquids based on d-glucose and MCPA or 2,4-D anions has been synthesized and the physicochemical, surface active and herbicidal properties of the obtained salts were characterized.

Self-assembly of isomannide-based monoesters of C18-fatty acids and their cellular uptake studies

The self-assembling behavior of oleic, elaidic and stearic acid-isomannide glycolipids is revealed.

Synthesis of Tertiary and Quaternary Amine Derivatives from Wood Resin as Chiral NMR Solvating Agents

Chiral tertiary and quaternary amine solvating agents for NMR spectroscopy were synthesized from the wood resin derivative (+)-dehydroabietylamine (2). The resolution of enantiomers of model compounds [Mosher’s acid (3) and its n-Bu₄N salt (4)] (guests) by (+)-dehydroabietyl-N,N-dimethylmethanamine (5) and its ten different ammonium salts (hosts) was studied. The best results with 3 were obtained using 5 while with 4 the best enantiomeric resolution was obtained using (+)-dehydroabietyl-N,N-dimethylmethanaminium bis(trifluoromethane-sulfonimide) (6). The compounds 5 and 6 showed a 1:1 complexation behaviour between the host and guest. The capability of 5 and 6 to recognize the enantiomers of various α-substituted carboxylic acids and their n-Bu₄N salts in enantiomeric excess (ee) determinations was demonstrated. A modification of the RES-TOCSY NMR pulse sequence is described, allowing the enhancement of enantiomeric discrimination when the resolution of multiplets is insufficient.

Exploring the synthesis of a new group of chiral ammonium salts with specific configurations at the stereogenic nitrogen centers

A group of new chiral dications with a fixed, specific configuration at the stereogenic nitrogen center was created. Stereoselective synthesis and recrystallization give the diastereomerically and enantiomerically pure dications, including a chiral amphiphile with surface-active properties.

Click reactions as a key step for an efficient and selective synthesis of D-xylose-based ILs

d-Xylose-based ionic liquids have been prepared from d-xylose following a five steps reaction sequence, the key step being a click cycloaddition. These ionic liquids (ILs) have been characterized through classical analytical methods (IR, NMR, mass spectroscopy, elemental analysis) and their stability constants, Tg and Tdec, were also determined. Considering their properties and their hydrophilicity, these compounds could be alternative solvents for chemical applications under mild conditions.

Chiral ionic liquids: a compendium of syntheses and applications (2005-2012)

In recent years, the field of chiral ionic liquids (CILs) has undergone exponential growth. As the technology has advanced, new ways of synthesizing stable and structurally diverse ionic liquids have been established. This has led to heretofore unknown applications of CILs as well as in improving efficiency of previously identified applications. In this review article we have compiled a comprehensive database containing structures and physical properties of notable CILs that have been synthesized during the last 6 years. Their applications in the fields of asymmetric organic synthesis, spectroscopy, and chromatography are also illustrated. This is an expansion of our previous review, which covered the literature before 2005.

New chiral imidazolium ionic liquids from isomannide

New chiral bis and mono-imidazolium ionic liquids derived from isomannide were synthesized. The structural features of the chiral organic cations impart a special arrangement of the chiral cavity. The new chiral chloride salts of isomannide derivatives are pivotal compounds for the synthesis of different organic ionic liquids. After metathesis different anions were associated to the chiral cations providing a new class of chiral ionic liquids.

Synthesis and applications of ionic liquids derived from natural sugars

Aiming to develop environmentally compatible chemical syntheses, the replacement of traditional organic solvents with ionic liquids (ILs) has attracted considerable attention. ILs are special molten salts with melting points below 100 degrees C that are typically constituted of organic cations (imidazolium, pyridinium, sulfonium, phosphonium, etc.) and inorganic anions. Due to their ionic nature, they are endowed with high chemical and thermal stability, good solvent properties, and non-measurable vapor pressure. Although the recovery of unaltered ILs and recycling partly compensate their rather high cost, it is important to develop new synthetic approaches to less expensive and environmentally sustainable ILs based on renewable raw materials. In fact, most of these alternative solvents are still prepared starting from fossil feedstocks. Until now, only a limited number of ILs have been prepared from renewable sources. Surprisingly, the most available and inexpensive raw material, i.e., carbohydrates, has been hardly exploited in the synthesis of ILs. In 2003 imidazolium-based ILs were prepared from o-fructose and used as solvents in Mizoroki-Heck and Diels-Alder reactions. Later on, the first chiral ILs derived from sugars were prepared from methyl D-glucopyranoside. In the same year, a family of new chiral ILs, obtained from commercial isosorbide (dianhydro-D-glucitol), was described. A closely related approach was followed by other researchers to synthesize mono- and bis-ammonium ILs from isomannide (dianhydro-D-mannitol). Finally, a few ILs bearing a pentofuranose unit as the chiral moiety were prepared using sugar phosphates as glycosyl donors and 1-methylimidazole as the acceptor.

A Facile Strategy to Tune the Chiral Recognition Capabilities of Chiral Ionic Liquids by Changing Achiral Alkyl Chain

A new series of chiral ionic liquids, utilizing cations derived from l-proline, have been synthesized in multi-gram scale, their specific rotations and chiral recognition capability can be adjusted by the alkylation of l-proline.