Synthesis of a water-soluble 2,2'-biphen[4]arene and its efficient complexation and sensitive fluorescence enhancement towards palmatine and berberine

Water soluble macrocyclic host for recognition of N-methylquinolinium salts in water

In this paper, we reported the synthesis of water soluble macrocyclic arenes 1 containing anionic carboxylate groups. It was found that host 1 could form a 1 : 1 complex with N-methylquinolinium salts in water. Moreover, the complexation and decomplexation of the complexes between host and the guests could be achieved by changing the pH of the solution, and the process could also be observed by naked eye.

Recent advances in the synthesis and applications of macrocyclic arenes

Macrocyclic arenes including calixarenes, resorcinarenes, cyclotriveratrylene, pillararenes and so on have emerged as highly attractive synthetic macrocyclic hosts due to their unique structures, facile functionalization, and broad range of applications. In recent years, there has been growing interest in the development of novel macrocyclic arenes composed of various aromatic building blocks bridged by methylene groups, which have found applications in various research areas. Consequently, the development of novel macrocyclic arenes has become a frontier and hot topic in supramolecular and macrocyclic chemistry. In this review, we feature the recent advances in the synthesis and applications of novel macrocyclic arenes that have emerged in the last decade. The general synthetic strategies employed for these macrocyclic arenes are systematically summarized, and their wide applications in molecular recognition and assemblies, molecular machines, biomedical science and functional materials are highlighted.

Biphen[n]arenes: Modular Synthesis, Customizable Cavity Sizes, and Diverse Skeletons

Macrocyclic compounds are fundamental tools in supramolecular chemistry and have been widely used in molecular recognition, biomedicine, and materials science. The construction of new macrocycles with distinctive structures and properties would unleash new opportunities for supramolecular chemistry. Traditionally popular macrocycles, e.g., cyclodextrins, calixarenes, cucurbiturils, and pillararenes, possess specific cavities that are usually less than 10 Å in diameter; they are normally suitable for accommodating small- or medium-sized guests but cannot engulf giant molecules or structures. Furthermore, the skeletons of traditional macrocycles are impoverished and incapable of being changed; functional substituents can be introduced only on their portals.Thus, it is very challenging to construct macrocycles with customizable cavity sizes and/or diverse backbones. We have developed a versatile and modular strategy for synthesizing macrocycles, namely, biphen[n]arenes (n = 3-8), based on the structure- or function-oriented replacement of reaction modules, functional modules, and linking modules. First, two reaction modules and one functional module are connected by Suzuki-Miyaura coupling to obtain a monomer having two reaction sites. Then Friedel-Crafts alkylation between the monomer and an aldehyde (linking module) serves to afford diversely functionalized macrocycles. Moreover, large macrocycles can be achieved by using long and rigid oligo(para-phenylene) monomers. Because of the modular synthesis and plentiful molecular supplies, the biphen[n]arenes showed interesting recognition properties for both small molecules and large polypeptides. Customizable functional backbones and binding sites endowed this new family of macrocycles with peculiar self-assembly properties and potential applications in gas chromatography, pollutant capture, and physisorptive separation. Biphen[n]arenes would be a promising family of workhorses in supramolecular chemistry.In this Account, we summarize our recent work on the chemistry of biphen[n]arenes. We introduce their design and modular synthesis, including systematic exploration for reaction modules, customizable cavity sizes, skeleton functionalization, pre- and postmodification, and molecular cages. Thereafter, we discuss their host-guest properties, involving the binding for small guests by cationic/anionic/neutral biphen[n]arenes, as well as the complexation of polypeptides by large quaterphen[n]arenes. In addition, we outline the self-assembly and potential applications of this new family of macrocycles. Finally, we forecast their further development. The chemistry of biphen[n]arenes is still in its infancy. Continued exploration will not only further expand the supramolecular toolbox but also open new avenues for the use of biphen[n]arenes in the fields of biology, pharmaceutical science, and materials science.

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

A small series of five novel berberine derivatives was synthesized by the Cu-catalyzed click reaction of 9-propargyladenine with 9-O-(azidoalkyl)berberine derivatives. The association of the resulting berberine-adenine conjugates with representative quadruplex-forming oligonucleotides 22AG dA(G3TTA)3G3 and a2 d(ACAG4TGTG4)2 was examined with photometric and fluorimetric titrations, thermal DNA denaturation analysis, and CD spectroscopy. The results from the spectrometric titrations indicated the formation of 2:1 or 1:1 complexes (ligand:G4-DNA) with log K b values of 10-11 (2:1) and 5-6 (1:1), which are typical for berberine derivatives. Notably, a clear relationship between the binding affinity of the ligands with the length of the alkyl linker chain, n, was not observed. However, depending on the structure, the ligands exhibited different effects when bound to the G4-DNA, such as fluorescent light-up effects and formation of ICD bands, which are mostly pronounced with a linker length of n = 4 (with a2) and n = 5 (with 22AG), thus indicating that each ligand-G4-DNA complex has a specific structure with respect to relative alignment and conformational flexibility of the ligand in the binding site. It was shown exemplarily with one representative ligand from the series that such berberine-adenine conjugates exhibit a selective binding, specifically a selectivity to quadruplex DNA in competition with duplex DNA, and a preferential thermal stabilization of the G4-DNA forms 22AG and KRAS. Notably, the experimental data do not provide evidence for a significant effect of the adenine unit on the binding affinity of the ligands, for example, by additional association with the loops, presumably because the adenine residue is sterically shielded by the neighboring triazole unit.

A Modular Synthetic Strategy for Functional Macrocycles

Reported here is a molecule-Lego synthetic strategy for macrocycles with functional skeletons, involving one-pot and high-yielding condensation between bis(2,4-dimethoxyphenyl)arene monomers and paraformaldehyde. By changing the blocks, variously functional units (naphthalene, pyrene, anthraquinone, porphyrin, etc.) can be conveniently introduced into the backbone of macrocycles. Interestingly, the macrocyclization can be tuned by the geometrical configuration of monomeric blocks. Linear (180°) monomer yield cyclic trimers and pentamers, while V-shaped (120°, 90° and 60°) monomers tend to form dimers. More significantly, even heterogeneous macrocycles are obtained in moderate yield by co-oligomerization of different monomers. This series of macrocycles have the potential to be prosperous in the near future.