The synthesis of a series of aromatic amide‐derived non‐biaryl atropisomers with a phosphine group and multiple stereogenic centers is reported. The novel phosphine ligands exhibit high diastereo‐ ...and enantioselectivities (up to >99:1 d.r., 95–99 % ee) as well as yields in the silver‐catalyzed asymmetric 3+2 cycloaddition of aldiminoesters with nitroalkenes, which provides a highly enantioselective strategy for the synthesis of optically pure nitro‐substituted pyrrolidines. In addition, the experimental results with regard to the carbon stereogenic center as well as the amide stereochemistry confirmed the potential of hemilabile atropisomers as chiral ligand in catalytic asymmetric 3+2 cycloaddition reaction.
New chiral ligands: Optically pure aromatic amide‐derived atropisomers were shown to be powerful phosphine ligands in the enantioselective silver‐catalyzed 3+2 cycloaddition. This method provides a highly efficient strategy for the synthesis of optically pure nitro‐substituted pyrrolidines with multiple stereogenic centers.
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•A comprehensive timeline of the transition metal-catalyzed ring-opening of four-membered silacycles is presented.•A comprehensive timeline of the transition metal-catalyzed ...ring-expansion reactions of four-membered silacycles is presented.•The synthesis of different types of silacyclobutane and its analogues under various reaction conditions is discussed.•The synthetic application of silacyclobutane and its analogues as organosilicon reagent in transition-metal catalysis is highlighted.•The mechanistic rationale of silicon-carbon bond cleavage and activations by transition-metal-based catalysts is outlined.
Silacyclobutanes (SCB), a family of useful organosilicon compounds, have attracted much attention because the highly strained silicon-carbon bond can be activated, as evidenced by transition-metal catalyzed ring-opening and ring expansion reactions. Efforts of extending silicon-carbon bond activation will definitely trigger powerful and privileged catalyst systems capable of unveiling opportunities for highly efficient and valuable transformations of SCB. This review summarized and highlighted representative and important advances for the synthesis of silacyclobutanes and its analogues as well as their catalytic transformations enabled by various transition-metal complexes whose versatility will be demonstrated widely in organosilicon chemistry and transition-metal catalysis. The different contributions in this growing research area summarized in this review could provide inspiration and incentive to make SCB as a precious source of organosilicon compounds.
Our previous work showed that a consortium of three plant growth-promoting rhizobacterium (PGPR) strains (Bacillus cereus AR156, Bacillus subtilis SM21, and Serratia sp. XY21), termed as BBS for ...short, was a promising biocontrol agent. The present study investigated its effect on drought tolerance in cucumber plants. After withholding watering for 13 days, BBS-treated cucumber plants had much darker green leaves and substantially lighter wilt symptoms than control plants. Compared to the control, the BBS treatment decreased the leaf monodehydroascorbate (MDA) content and relative electrical conductivity by 40% and 15%, respectively; increased the leaf proline content and the root recovery intension by 3.45-fold and 50%, respectively; and also maintained the leaf chlorophyll content in cucumber plants under drought stress. Besides, in relation to the control, the BBS treatment significantly enhanced the superoxide dismutase (SOD) activity and mitigated the drought-triggered down-regulation of the expression of the genes cAPX, rbcL, and rbcS encoding cytosolic ascorbate peroxidase, and ribulose-1,5-bisphosphate carboxy/oxygenase (Rubisco) large and small subunits, respectively, in cucumber leaves. However, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity was undetected in none of the culture solutions of three BBS constituent strains. These results indicated that BBS conferred induced systemic tolerance to drought stress in cucumber plants, by protecting plant cells, maintaining photosynthetic efficiency and root vigor and increasing some of antioxidase activities, without involving the action of ACC deaminase to lower plant ethylene levels.
Cancer incidence is rising, and the efficacy of current available anticancer agents is limited by severe dose‐limiting toxicities and drug resistance problems. Nanoparticles are heralded as the next ...frontier in cancer treatment. Here, a pure physical method is used to efficiently fabricate very small silver particles even approaching the Ångstrom (Ång) dimension. Fructose is used as a dispersant and stabilizer to coat the Ång‐scale silver particles (AgÅPs). Functional and mechanistic studies demonstrate that fructose‐coated AgÅPs (F‐AgÅPs) can enter and accumulate in multiple cultured cancer cell lines to induce apoptotic death, whereas most normal cells are resistant to the efficacious dose of F‐AgÅPs; in vivo, intravenous administration of F‐AgÅPs potently inhibits the growth of pancreatic and lung cancer xenografts in nude mice, without inducing notable toxic effects on the healthy tissues. The results suggest the promising potential of F‐AgÅPs as a potent, safe, and broad‐spectrum agent for the cancer treatment.
Physical method‐fabricated fructose‐coated Ångstrom‐scale silver particles (F‐AgÅPs) have the ability to enter multiple cancer cells to induce apoptosis. Intravenous injection of F‐AgÅPs potently inhibits the growth of cancer xenograft models, without inducing notable toxic effects on healthy tissues. These results suggest that F‐AgÅPs have a great potential to be used as a potent, safe, and broad‐spectrum agent for cancer treatment.
Alzheimer's disease (AD) is currently ranked as the third leading cause of death for eldly people, just behind heart disease and cancer. Autophagy is declined with aging. Our study determined the ...biphasic changes of miR-331-3p and miR-9-5p associated with AD progression in APPswe/PS1dE9 mouse model and demonstrated inhibiting miR-331-3p and miR-9-5p treatment prevented AD progression by promoting the autophagic clearance of amyloid beta (Aβ).
The biphasic changes of microRNAs were obtained from RNA-seq data and verified by qRT-PCR in early-stage (6 months) and late-stage (12 months) APPswe/PS1dE9 mice (hereinafter referred to as AD mice). The AD progression was determined by analyzing Aβ levels, neuron numbers (MAP2
) and activated microglia (CD68
IBA1
) in brain tissues using immunohistological and immunofluorescent staining. MRNA and protein levels of autophagic-associated genes (
) were tested to determine the autophagic activity. Morris water maze and object location test were employed to evaluate the memory and learning after antagomirs treatments in AD mice and the Aβ in the brain tissues were determined.
MiR-331-3p and miR-9-5p are down-regulated in early-stage of AD mice, whereas up-regulated in late-stage of AD mice. We demonstrated that miR-331-3p and miR-9-5p target autophagy receptors Sequestosome 1 (
) and Optineurin (
), respectively. Overexpression of miR-331-3p and miR-9-5p in SH-SY5Y cell line impaired autophagic activity and promoted amyloid plaques formation. Moreover, AD mice had enhanced Aβ clearance, improved cognition and mobility when treated with miR-331-3p and miR-9-5p antagomirs at late-stage.
Our study suggests that using miR-331-3p and miR-9-5p, along with autophagic activity and amyloid plaques may distinguish early versus late stage of AD for more accurate and timely diagnosis. Additionally, we further provide a possible new therapeutic strategy for AD patients by inhibiting miR-331-3p and miR-9-5p and enhancing autophagy.
An enantioselective oxidative C–H/N–H carbonylation process was developed in this work. A bimetallic Pd/Cu-based catalyst system was found to catalyze enantioselective C(sp2)–H carbonylation of ...prochiral arylsulfonamides via desymmetrization process in the presence of mono-N-protected amino acid ligands. This reaction provides a facile strategy to the stereoselective construction of the lactam-type products, such as isoindoline-1-ones and isoquinoline-1-ones, in good yields and enantioselectivities under balloon pressure with the mixture of CO/O2. The reaction mechanism was rationalized by using density functional theory (DFT) study.
A differentiation switch of bone marrow mesenchymal stem/stromal cells (BMSCs) from osteoblasts to adipocytes contributes to age‐ and menopause‐associated bone loss and marrow adiposity. Here it is ...found that osteocytes, the most abundant bone cells, promote adipogenesis and inhibit osteogenesis of BMSCs by secreting neuropeptide Y (NPY), whose expression increases with aging and osteoporosis. Deletion of NPY in osteocytes generates a high bone mass phenotype, and attenuates aging‐ and ovariectomy (OVX)‐induced bone‐fat imbalance in mice. Osteocyte NPY production is under the control of autonomic nervous system (ANS) and osteocyte NPY deletion blocks the ANS‐induced regulation of BMSC fate and bone‐fat balance. γ‐Oryzanol, a clinically used ANS regulator, significantly increases bone formation and reverses aging‐ and OVX‐induced osteocyte NPY overproduction and marrow adiposity in control mice, but not in mice lacking osteocyte NPY. The study suggests a new mode of neuronal control of bone metabolism through the ANS‐induced regulation of osteocyte NPY.
Normally, norepinephrine (NE) and acetylcholine (ACh) production is maintained at a balanced level in bone, so that osteocytes cannot generate excessive neuropeptide Y (NPY) to favor bone marrow mesenchymal stem/stromal cell adipogenesis rather than osteogenesis. With aging/estrogen deficiency, sympathetic overactivity, and decreased parasympathetic activity cause NE overproduction and ACh reduction, resulting in excess osteocyte NPY generation and subsequent bone‐fat imbalance.
In this work, we have successfully determined that the aromatic amide-derived nonbiaryl atropisomer/silver complex (silver-Xing-Phos) is an effective catalyst system for the solvent-dependent ...exo-selective cycloaddition of glycine aldimino esters with chalcones or less-reactive methyl cinnamates to give the corresponding chalcone- or cinnamate-derived pyrrolidines with multiple stereogenic centers in good yields and high diastereoselectivities as well as excellent enantioselectivities. Remarkably, it is the first example of highly enantioselective silver-catalyzed 3 + 2 cycloaddition of methyl cinnamates with glycine aldimino esters.
In order to optimize the performance of La2NiO4+δ materials as H–SOFC cathodes, different Ca doping amounts (x = 0, 0.25, 0.5, 0.75) is adopted to find the best solution. Doping with Ca in La2NiO4+δ ...can effectively improve the electrical conductivity and the ORR activity of the cathode surface, which have good chemical stability and compatible TEC with the electrolyte. Electrochemical studies reveal that La1.5Ca0.5NiO4+δ cathode shows the best electrochemical performance in single cell tests outputing the maximum power density (MPD) of 923 mW cm−2 and the polarization resistance (R p) of 0.053 Ω cm2 at 700 °C. This work indicates that the single-phase R–P layered material La1.5Ca0.5NiO4+δ could be a promising cathode for H–SOFC.
•Structure and electrical properties of La2-xCaxNiO4+δ (x = 0–0.75) were studied.•Doping with Ca was shown to increase the electrical conductivity.•Ca-doping could boost chemical structure stablility and electrolyte compatibility.•Cathode surface properties have a strong influence on the performance of the cell.•The La1.5Ca0.5NiO4+δ cathode can achieve high performance of 923 mW cm−2 at 700 °C.
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