Incorporation of an Isohexide Subunit Improves the Drug-like Properties of Bioactive Compounds

An enhanced ability to pre-engineer favorable drug-likeness qualities into bioactive molecules would focus and streamline the drug development process. We find that phenols, carboxylic acids, and a purine react with isosorbide ("GRAS" designated) under Mitsunobu coupling conditions to deliver the isoidide conjugates selectively and efficiently. Such conjugates show improved solubility and permeability properties compared with the bare scaffold compounds themselves, and the purine adduct may have applications as a 2'-deoxyadenosine isostere. We anticipate additional benefits, implied by their structures, in metabolic stability and reduced toxicity of the isoidide conjugates as well.

An Efficient and Practical Chemoenzymatic Route to (3R,3aR,6R,6aR)-Hexahydrofuro[3,2-b]furan-6-amino-3-ol (6-Aminoisomannide) from Renewable Sources

The synthesis of 6-aminoisomannide is easily achieved starting from the renewable, inexpensive, and commercially available isosorbide in 66% overall yield. A biocatalyzed highly regioselective acetylation of the 3-endo hydroxyl group of isosorbide was followed by the stereospecific interconversion of the 6-exo hydroxyl group into an azido group, through reaction with trifluoromethanesulfonic anhydride, followed by nucleophilic displacement of the triflate group by sodium azide. Finally, reduction of the azido group and deacetylation of the 3-hydroxy group were performed in one pot using LiAlH4.

K, Rayadurgam J, Rajasekhara Reddy S. Naturally derived sugar-based ionic liquids: an emerging tool for sustainable organic synthesis and chiral recognition

In the past decade, the synthesis of sugar-based ionic liquids (SILs) from natural sugars has been described as a promising strategy.

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.

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.

The Relationship between the Structure and Properties of Amino Acid Ionic Liquids

Ionic liquids based on different l-amino acids (glycine, l-valine, l-leucine, l-isoleucine, l-histidine, l-methionine, l-tyrosine, l-tryptophan, l-arginine, and l-threonine) and different cations (tetrabutylammonium (TBA), tributylmethylammonium (tBMA), didecyldimethylammonium (DDA), (2-hydroxyethyl)trimethylammonium (choline) (Chol), alkyl(C₁₂-C₁₄) dimethylbenzylammonium (benzalkonium) (BA), dodecyltrimethylammonium (DDTMA), hexadecyltrimethylammonium (HDTMA), octadecyltrimethylammonium (ODTMA) and 1-ethyl-3-methylimidazolium (EMIM)) have been synthesized and characterized by NMR and FTIR. Viscosity, specific rotation, surface activity, thermal stability (TG), and phase transformations (DSC) have been determined and compared with available data. Furthermore, benzalkonium, didecyldimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, and octadecyltrimethylammonium amino acid ionic liquids have been shown to exhibit surface activity. The dissolution of cellulose in amino acid ionic liquids (AAILs) composed of various cations was also investigated. Cellulose was only dissolved in EMIM salts of amino acids. In particular, the influence of the cation type on selected physicochemical and spectroscopic properties were discussed. The article is a mini review on amino acid ionic liquids.

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.

Isohexide Dinitriles: A Versatile Family of Renewable Platform Chemicals

Building blocks of isohexides extended by one carbon atom at the 2- or 5-positions are now synthetically accessible by a convenient, selective, base-catalyzed epimerization of the corresponding dinitriles. Kinetic experiments using the strong organic base 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) show that all three possible isohexide dinitrile isomers exist within a dynamic equilibrium. An epimerization mechanism based on density functional theory (DFT) calculations is proposed. Structural identification of all three possible isomers is based on NMR analysis and single crystal x-ray crystallography. DFT calculations confirm that the observed crystal structures are indeed the lowest energy conformers of these isohexide derivatives.

Mutagenic activity of quaternary ammonium salt derivatives of carbohydrates

This paper presents a study on a series of quaternary ammonium salt (QAS) derivatives of glucopyranosides with an elongated hydrophobic hydrocarbon chain. The new N-[6-(β-D-glucopyranosyloxy)hexyl]ammonium bromides and their O-acetyl derivatives were analyzed via (1)H and (13)C NMR spectroscopy. The mutagenic activity of the newly synthesized QAS was investigated using two different techniques: The Vibrio harveyi luminescence assay and the Ames test. The obtained results support previous findings contesting QAS safety and indicate that QAS, specifically pyridinium derivatives, might be mutagenic.

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.

Biosourced 1,2,3-triazolium ionic liquids derived from isosorbide

The drastic influence of 1,4-3,6-dianhydrohexitols stereochemistry on physical, thermal and ion conducting properties.

Conversion of cellulose into isosorbide over bifunctional ruthenium nanoparticles supported on niobium phosphate

Considerable effort has been applied to the development of new processes and catalysts for cellulose conversion to valuable platform chemicals. Isosorbide is among the most interesting products as it can be applied as a monomer and building block for the future replacement of fossil resource-based products. A sustainable method of isosorbide production from cellulose is presented in this work. The strategy relies on a bifunctional Ru catalyst supported on mesoporous niobium phosphate in a H2 atmosphere under pressure without further addition of any soluble acid. Over 50 % yield of isosorbide with almost 100 % cellulose conversion can be obtained in 1 h. The large surface area, pore size, and strong acidity of mesoporous niobium phosphate promote the hydrolysis of cellulose and dehydration of sorbitol; additionally, the appropriate size of the supported Ru nanoparticles avoids unnecessary hydrogenolysis of sorbitol. Under a cellulose/catalyst mass ratio of 43.3, the present bifunctional catalyst could be stably used up to six times, with its mesoporous structure well preserved and without detectable Ru leaching into the reaction solution.

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.

Isosorbide as a renewable platform chemical for versatile applications--quo vadis?

Isosorbide is a platform chemical of considerable importance for the future replacement of fossil resource-based products. Applications as monomers and building blocks for new polymers and functional materials, new organic solvents, for medical and pharmaceutical applications, and even as fuels or fuel additives are conceivable. The conversion of isosorbide to valuable derivatives by functionalization or substitution of the hydroxyl groups is difficult because of the different configurations of the 2- and 5-positions and the resulting different reactivity and steric hindrance of the two hydroxyl groups. Although a substantial amount of work has been published using exclusively the endo or exo derivatives isomannide and isoidide, respectively, as starting material, a considerable effort is still necessary to transfer and adapt these methods for the efficient conversion of isosorbide. This Minireview deals with all aspects of isosorbide chemistry, which includes its production by catalytic processes, special properties, and chemical transformations for its utilization in biogenic polymers and other applications of interest.

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.

Oxidative addition reaction of diarylplatinum(II) complexes with MeI in ionic liquid media: a kinetic study

A kinetic study of the oxidative addition reaction of diarylplatinum(II) complexes [Pt(p-MeC(6)H(4))(2)(NN)] (1a: NN = 1,10-phenanthroline (phen) and 1b: NN = 4,4'-di-tert-butyl-2,2'-bipyridine ((t)Bu(2)bpy)) with MeI in ionic liquids 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][bta]) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]) is described. The reactions were investigated as a function of MeI concentration and temperature under pseudo-first-order conditions using UV-vis spectroscopy techniques. In general, the oxidative addition reactions in ionic liquids followed an S(N)2 mechanism, similar to that reported for the related reactions in conventional solvents, e.g. benzene or acetone. The reaction rates in different solvents followed the order acetone > ionic liquids > benzene. The trend in the values of k(2) clearly indicated that ionic liquids behave like conventional solvents and that no particular 'ionic liquid effect' was detected in this kind of reaction. The effect of solvent on the reactions was examined using a linear solvation energy relationship (LSER) based on the Kamlet-Taft solvent scale. The activation parameters, DeltaH(++) and DeltaS(++), were obtained for the reactions in each solvent and the investigation of enthalpy-entropy compensation confirmed that the mechanism operated in all solvents is similar.