We summarize in this review the recent development of chiral phosphoric acid (CPA)-catalyzed asymmetric dearomatization reactions. A wide array of electron-rich arenes (indoles, phenols, naphthols, ...benzothiophenes, benzofurans,
etc.
) and electron-poor arenes (pyridines, quinolines, isoquinolines,
etc.
) has been proved reactive towards various reaction partners in the presence of a CPA catalyst, enabling asymmetric dearomatization reactions that lead to structurally-diverse polycyclic molecules. The reactions are grouped according to the roles of the arenes in the reactions (as nucleophiles or electrophiles) and the types of reaction partners. This review closes with a personal perspective on the dynamic research area of asymmetric dearomatization reactions by CPAs.
We summarize in this review the recent development of chiral phosphoric acid (CPA)-catalyzed asymmetric dearomatization reactions.
Aiming at the construction of novel platform for efficient light harvesting, the precise synthesis of a new family of AIEgen‐branched rotaxane dendrimers was successful realized from an ...AIEgen‐functionalized 2rotaxane through a controllable divergent approach. In the resultant AIE macromolecules, up to twenty‐one AIEgens located at the tails of each branches, thus making them the first successful example of AIEgen‐branched dendrimers. Attributed to the solvent‐induced switching feature of the rotaxane branches, the integrated rotaxane dendrimers displayed interesting dynamic feature upon the aggregation‐induced emission (AIE) process. Moreover, novel artificial light‐harvesting systems were further constructed based on these AIEgen‐branched rotaxane dendrimers, which revealed impressive generation‐dependent photocatalytic performances for both photooxidation reaction and aerobic cross‐dehydrogenative coupling (CDC) reaction.
A novel artificial light‐harvesting system based on AIEgen‐branched rotaxane dendrimers has been successfully constructed which displayed impressive generation‐dependent photocatalytic performances for both photooxidation reaction and aerobic cross‐dehydrogenative coupling reaction.
The ubiquitin‐proteasome system (UPS) is a rapid regulatory mechanism for selective protein degradation in plants and plays crucial roles in growth and development. There is increasing evidence that ...the UPS is also an integral part of plant adaptation to environmental stress, such as drought, salinity, cold, nutrient deprivation and pathogens. This review focuses on recent studies illustrating the important functions of the UPS components E2s, E3s and subunits of the proteasome and describes the regulation of proteasome activity during plant responses to environment stimuli. The future research hotspots and the potential for utilization of the UPS to improve plant tolerance to stress are discussed.
The ubiquitin‐proteasome system (UPS) plays crucial roles in plant responses to environment stimuli through degrading distinct target proteins. This review summaries recent progress in our understanding of the regulation of UPS components, subunits and proteasome activity under abiotic and biotic stress, and future research hotspots are discussed.
Isoselenazolone derivatives have attracted significant research interest because of their potent therapeutic activities and indispensable applications in organic synthesis. Efficient construction of ...functionalized isoselenazolone scaffolds is still challenging, and thus new synthetic approaches with improved operational simplicity have been of particular interest. In this manuscript, we introduce a rhodium‐catalyzed direct selenium annulation by using stable and tractable elemental selenium. A series of benzamides as well as acrylamides were successfully coupled with selenium under mild reaction conditions, and the obtained isoselenazolones could be pivotal synthetic precursors for several organoselenium compounds. Based on the designed control experiments and X‐ray absorption spectroscopy measurements, we propose an unprecedented selenation mechanism involving a highly electrophilic Se(IV) species as the reactive selenium donor. The reaction mechanism was further verified by a computational study.
A Rh(III)‐catalyzed direct selenium annulation by using stable and tractable elemental selenium is developed. A series of benzamides as well as acrylamides were successfully coupled with selenium under mild reaction conditions to give isoselenazolone derivatives. An unprecedented selenation mechanism involving an electrophilic Se(IV) species as the reactive selenium donor is proposed based on the designed control experiments, X‐ray absorption spectroscopy, and computational study.
Alzheimer’s disease (AD) is the most common form of dementia characterized by progressive loss of cognitive functions due to neuronal death mainly in the hippocampal and cortical brain. Sulforaphene ...(SF) is one of the main isothiocyanates isolated from a Chinese herb Raphani Semen. In this study, we aimed to investigate the neuroprotective effects of SF using in vitro and in vivo models of AD. Streptozotocin (STZ) was intracranially injected into the rats; then, SF (25 and 50 mg/kg) was given orally once a day for 6 consecutive weeks. After drug treatment, the cognitive functions were assessed using the Morris Water Maze Test (MWMT). After the MWMT, the rats were euthanized and brain tissues were collected. In the in vitro test, BV-2 microglia were pretreated with SF (1 and 2 μM) for 1 h and then stimulated with lipopolysaccharide (LPS) for another 23 h. Both molecular and histological methods were used to unravel the action mechanisms and elucidate the signaling pathway. The MWMT results showed that SF treatment significantly improved the STZ-induced cognitive deficits in rats. SF treatment markedly suppressed the production of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) but increased the release of IL-10 in the STZ-treated rats. In addition, SF significantly inhibited the phosphorylation of tau protein at Thr205, Ser396, and Ser404 sites, while enhancing the ratios of p-Akt (Ser473)/Akt and p-GSK-3β (Ser9)/GSK-3β in the hippocampus of the STZ-treated rats. On the other hand, SF (1 and 2 μM) treatment also markedly attenuated the cytotoxicity induced by LPS in BV-2 cells. In addition, SF treatment obviously suppressed the releases of nitric oxide (NO), TNF-α, and IL-6 in the LPS-stimulated BV-2 cells. Moreover, SF treatment significantly mitigated the nuclear translocation of p-NF-κB p65 and the ratio of p-GSK-3β (Ser9)/GSK-3β in LPS-stimulated BV-2 cells. Taken together, SF possessed neuroprotective effects against the STZ-induced cognitive deficits in rats and LPS-induced neuroinflammation in BV-2 cells via modulation of the PI3K/Akt/GSK-3β pathway and inhibition of the NF-κB activation, suggesting that SF is a promising neuroprotective agent worthy of further development into AD treatment.
Single‐electron transfer (SET) oxidation of ionic hypervalent complexes, in particular alkyltrifluoroborates (Alkyl‐BF3−) and alkylbis(catecholato)silicates (Alkyl‐Si(cat)2−), have contributed ...substantially to alkyl radical generation compared to alkali or alkaline earth organometallics because of their excellent activity–stability balance. Herein, another proposal is reported by using neutral metalloid compounds, Alkyl‐GeMe3, as radical precursors. Alkyl‐GeMe3 shows comparable activity to that of Alkyl‐BF3− and Alkyl‐Si(cat)2− in radical addition reactions. Moreover, Alkyl‐GeMe3 is the first successful group 14 tetraalkyl nucleophile in nickel‐catalyzed cross‐coupling. Meanwhile, the neutral nature of these organogermanes offset the limitation of ionic precursors in purification and derivatization. A preliminary mechanism study suggests that an alkyl radical is generated from a tetraalkylgermane radical cation with the assistance of a nucleophile, which may also result in the development of more non‐ionic alkyl radical precursors with a metalloid center.
Alkyl‐GeMe3 was proven to be an effective radical precursor under visible‐light photocatalysis. The metalloid nature of Ge allows single‐electron transfer (SET) at the neutral Ge center and leads to advantages in separation and derivatization.
Accurate control of the layer number of orderly stacked 2D polymers has been an unsettled challenge in self‐assembly. Herein we describe the fabrication of a bilayer 2D supramolecular organic ...framework from a monolayer 2D supramolecular organic framework in water by utilizing the cooperative coordination of a rod‐like bipyridine ligands to zinc porphyrin subunits of the monolayer network. The monolayer supramolecular framework is prepared from the co‐assembly of an octacationic zinc porphyrin monomer and cucurbit8uril (CB8) in water through CB8‐encapsulation‐promoted dimerization of 4‐phenylpyridiunium subunits that the zinc porphyrin monomer bear. The bilayer 2D supramolecular organic framework exhibits structural regularity in both solution and the solid state, which is characterized by synchrotron small‐angle X‐ray scattering and high‐resolution transmission electron microscopic techniques. Atomic force microscopic imaging confirms that the bilayer character of the 2D supramolecular organic framework can be realized selectively on the micrometer scale.
Generation of a bilayer 2D supramolecular organic framework is realized by hierarchical assembly in water. The coordination of a rod‐like bipyridine ligand to the zinc porphyrin subunits of a monolayer supramolecular network has been utilized to selectively produce ordered bilayer supramolecular architectures with controlled thickness.
Rheumatoid arthritis (RA) is one of the chronic systemic autoimmune diseases that cardinally affect the joints. Many people all over the world suffer from the disease. Fibroblast‐like synoviocytes ...(FLSs) play a significant role in the occurrence and development of RA. The long noncoding RNA maternally expressed gene 3 (MEG3) is an imprinted gene, which participates in various cancers as a tumor suppressor. Previous studies have shown that nucleotide oligomerization domain (NOD)‐like receptors 5 (NLRC5) plays a key role in inflammatory and autoimmune diseases. Nonetheless, we know very little about the biofunctionality of MEG3 during the development of RA. In this paper, we used complete Freund's adjuvant (CFA)‐induced rats as RA animal models. The level of MEG3 significantly reduced in CFA‐induced synovial tissues and FLSs, whereas the NLRC5 levels were increased. Enforced expression of MEG3 may be responsible for the decreased level of NLRC5 and inflammatory cytokine level. The results of methylation‐specific PCR suggested that the MEG3 gene promoter was significantly methylated in CFA‐induced synovial tissues and FLSs. More important, hypermethylation of MEG3 promoter could be inhibited by 5‐aza‐2‐deoxycytidine (5‐azadC; methylation inhibitor). Besides, the expression of NLRC5 significantly decreased followed by 5‐azadc. Furthermore, DNA methyltransferases 1 (DNMT1) increased in CFA‐induced synovial tissues and cells. These results indicated that MEG3 regulates RA by targeting NLRC5 potentially.
Maternally expressed gene 3 (MEG3) may be involved in the development of rheumatoid arthritis (RA) by affecting the proliferation of fibroblast‐like synoviocytes (FLSs), whereas nucleotide oligomerization domain (NOD)‐like receptors 5 (NLRC5) promotes proliferation of FLSs in RA. Enforced expression of MEG3 decreased NLRC5 expression. These results further verified that MEG3 regulates RA by targeting NLRC5 potentially.
The construction of circularly polarized luminescence (CPL) switches with multiple switchable emission states and high dissymmetry factors (glum) has attracted increasing attention due to their broad ...applications in diverse fields such as the development of smart devices and sensors. Herein, a new family of AIE‐active chiral 3rotaxanes were designed and synthesized, from which a novel CPL switching system was successfully constructed. The switching process was realized through the controlled motions of the chiral pillar5arene macrocycles along the axle through the addition or removal of the acetate anions, which not only modulated the chirality information transfer but also tuned the aggregations of the integrated 3rotaxanes, thus resulting in reversible transformations between two emission states with both high photoluminescence quantum yields (PLQYs) and high dissymmetry factors (glum) values.
The marriage of a switchable rotaxane and an AIEgen gave rise to the successful construction of a novel chiral 3rotaxane‐based CPL switching system with large glum values, remarkable difference in the glum values, and excellent cycling ability.
Most two-dimensional (2D) covalent organic frameworks (COFs) are non-fluorescent in the solid state even when they are constructed from emissive building blocks. The fluorescence quenching is usually ...attributed to non-irradiative rotation-related or π-π stacking-caused thermal energy dissipation process. Currently there is a lack of guiding principle on how to design fluorescent, solid-state material made of COF. Herein, we demonstrate that the eclipsed stacking structure of 2D COFs can be used to turn on, and tune, the solid-state photoluminescence from non-emissive building blocks by the restriction of intramolecular bond rotation via intralayer and interlayer hydrogen bonds among highly organized layers in the eclipse-stacked COFs. Our COFs serve as a platform whereby the size of the conjugated linkers and side-chain functionalities can be varied, rendering the emission colour-tuneable from blue to yellow and even white. This work provides a guide to design new solid-state emitters using COFs.
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