Synthesis of a novel resorcin[4]arene–glucose conjugate and its catalysis of the CuAAC reaction for the synthesis of 1,4-disubstituted 1,2,3-triazoles in water

Molecular vessels from preorganised natural building blocks

Supramolecular vessels emerged as tools to mimic and better understand compartmentalisation, a central aspect of living matter. However, many more applications that go beyond those initial goals have been documented in recent years, including new sensory systems, artificial transmembrane transporters, catalysis, and targeted drug or gene delivery. Peptides, carbohydrates, nucleobases, and steroids bear great potential as building blocks for the construction of supramolecular vessels, possessing complexity that is still difficult to attain with synthetic methods - they are rich in functional groups and well-defined stereogenic centers, ready for noncovalent interactions and further functions. One of the options to tame the functional and dynamic complexity of natural building blocks is to place them at spatially designed positions using synthetic scaffolds. In this review, we summarise the historical and recent advances in the construction of molecular-sized vessels by the strategy that couples synthetic predictability and durability of various scaffolds (cyclodextrins, porphyrins, crown ethers, calix[n]arenes, resorcin[n]arenes, pillar[n]arenes, cyclotriveratrylenes, coordination frameworks and multivalent high-symmetry molecules) with functionality originating from natural building blocks to obtain nanocontainers, cages, capsules, cavitands, carcerands or coordination cages by covalent chemistry, self-assembly, or dynamic covalent chemistry with the ultimate goal to apply them in sensing, transport, or catalysis.

Copper(I)-Catalyzed Alkyne-Azide Cycloaddition (CuAAC) "Click" Reaction: A Powerful Tool for Functionalizing Polyhydroxylated Platforms

Click chemistry is currently one of the most used tools for the generation of complex organic molecules. The advantages of using click chemistry in organic synthesis are remarkable; in many cases, the reactions occur under mild conditions and are free of solvents, with high yields and short reaction times. This makes it an extraordinarily effective and viable alternative for obtaining complex/conjugated molecules. In this review, the use of click chemistry CuAAC is especially emphasized for polyhydroxylated platforms such as resorcinarenes or calixarenes, focusing mainly on aspects of synthesis, specifically conditions, reagents, and methodologies.

Synthesis and Self-Assembling Properties of Peracetylated β-1-Triazolyl Alkyl D-Glucosides and D-Galactosides

Carbohydrate-based low-molecular-weight gelators (LMWGs) are useful classes of compounds due to their numerous applications. Among sugar-based LMWGs, certain peracetylated sugar beta-triazole derivatives were found to be effective organogelators and showed interesting self-assembling properties. To further understand the structural influence towards molecular assemblies and obtain new functional materials with interesting properties, we designed and synthesized a library of tetraacetyl beta-1-triazolyl alkyl-D-glucosides and D-galactosides, in which a two or three carbon spacer is inserted between the anomeric position and the triazole moiety. A series of 16 glucose derivatives and 14 galactose derivatives were synthesized and analyzed. The self-assembling properties of these new triazole containing glycoconjugates in different solvents were analyzed. Several glucose derivatives were found to be effective LMWGs, with compound 7a forming gels in a variety of organic solvents as well as in the presence of metal ions in aqueous solutions. The organogels formed by several compounds were characterized using optical microscopy, atomic force microscopy (AFM) and UV-vis spectroscopy, etc. The co-gels formed by compound 7a with the Fmoc derivative 7i showed interesting fluorescence enhancement upon gelation. Several gelators were also characterized using powder X-ray diffraction and FT-IR spectroscopy. The potential applications of these sugar-based gelators for drug delivery and dye removal were also studied.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

Thiocyanation and 2-Amino-1,3-thiazole Formation in Water Using Recoverable and Reusable Glycosylated Resorcin[4]arene Cavitands

A family of three spatially directional resorcin[4]arene cavitand glycoconjugates (RCGs) have been applied as efficient recoverable and reusable inverse phase transfer catalysts for eco- and environmentally friendly thiocyanation and 2-amino-1,3-thiazole formation reactions in water. The results show that RCGs (1 mol %) were capable of hosting and catalyzing various water-insoluble bromo/thiocyanato substrates in water without the use of any co-organic solvents. The recoverability and reusability of RCG catalytic systems, that is, RCG1 and RCG3, were also examined upon a simple extraction of the desired products using DCM or ethyl acetate, followed by subjecting the recovered aqueous solution containing the RCG catalysts to the next reaction cycles.

Multivalent Allyl-Substituted Macrocycles as Nonaggregating Building Blocks

Based on the concept of dual-directionality, the synthesis of two novel zinc(II)-containing phthalocyanine (Pc-ene1) and azaphthalocyanine (AzaPc-ene1) macrocycles bearing dual directional (up/down) allyl moieties on their rims is reported. Their structural identification, that is, NMR, FT-IR, UV-vis, MALDI-TOF spectral data, single crystal X-ray diffraction, and CHN elemental analyses, along with their nonaggregating behaviors in solvated media and crystalline forms has been confirmed.