Latest ArticlesThe utilization of readily available amino acids, which is not only an oxygen nucleophile but also a nitrogen nucleophile, in palladium-catalyzed allylic substitution is realized under mild conditions. The chemoselectivity and multiple allylation are controlled by adjusting the reaction conditions. This represents the first example of this convenient access to valuable N,O-diallylated amino acids. Under the title conditions, a range of amino acids (α-, β-, γ-) and dipeptides can be readily converted in to the corresponding allylic products with excellent yields (67 examples, up to 99% yield) as well as good functional group tolerance.
Although multitudinous nanoscale drug-delivery systems (DDSs) have been recommended to improve anti-ulcerative colitis (UC) outcomes, to enhance the mucoadhesion of nanosystems on the colon and specifically release the loaded drugs in response to the colon micro-environment would be critical factors. The application of curcumin (Cur), an acknowledged anti-UC phytochemical compound, for UC therapy requires more efficient nano-carriers to improve its therapeutic outcome. Herein, we developed the colon-targeted nano-micelles with mucoadhesive effect and Azo reductase-triggered drug release profiles for Cur delivery in UC treatment. Specifically, the amphiphilic block polymer containing the Azo-reductase sensitive linkage (PEG-Azo-PLGA), and catechol-modified TPGS (Cat-TPGS) were synthesized respectively. Based on the self-assembly of the mixed polymers, Cur-micelles (142.7 ± 1.7 nm of average size, 72.36% ± 1.54% of DEE) were obtained. Interestingly, the Cur-micelles exhibited the Azo-reductase sensitive particle dissociation and drug release, the enhanced cellular uptake and the prolonged retention on colonic mucosa, mediated by the strong mucoadhesion of catechol structure. Ultimately, Cur-micelles significantly mitigated colitis symptoms and accelerated colitis repair in DSS-treated mice by regulating the intestinal flora and the levels of pro-inflammatory factors (MPO, IL-6, IL-1β, and TNF-α) related to TLR4/MyD88/NF-κB signaling pathway. This work provides an effective drug delivery strategy for anti-UC drugs by oral administration.
Heterogeneous transition metal catalysts are indispensable in improving environmental pollution. However, their fabrication is often costly and cumbersome, and they can easily pollute the environment. This study proposed using a natural Gabonese ore (GBO) containing MnxOy and FexOy as catalysts to degrade orange Ⅱ (OII) via peroxymonosulfate (PMS) activation. The GBO + PMS system exhibited extraordinarily high stability and catalytic activity towards OII elimination (92.2%, 0.0453 min−1). The reactive oxygen species (ROS) generated in the system were identified using radical scavenging tests and electron spin-resonance (ESR) analysis. Singlet oxygen (1O2) represented the dominant reactive species for OII degradation, while the system presented a lower reaction energy barrier and was effective in a broad pH range (2–10). This work also proposed the activation mechanism for the GBO + PMS system and OII degradation pathways. This study revealed a new approach for exploring inexpensive, eco-friendly, efficient, and stable heterogeneous transition metal catalysts.
A novel type of host–guest recognition systems have been developed on the basis of a Au(Ⅲ) molecular tweezer receptor and chiral Pt(Ⅱ) guests. The complementary host–guest motifs display high non-covalent binding affinity (Ka: ~104 L/mol) due to the participation of two-fold intermolecular π–π stacking interactions. Both phosphorescence and chirality signals of the Pt(Ⅱ) guests strengthen in the resulting host–guest complexes, because of the cooperative rigidifying and shielding effects rendered by the tweezer receptor. Their intensities can be reversibly switched toward pH changes, by taking advantage of the electronic repulsion effect between the protonated form of tweezer receptor and the positive-charged guests in acidic environments. Overall, the current study demonstrates the feasibility to enhance and modulate phosphorescence and chirality signals simultaneously via molecular tweezer-based host–guest recognition.
Herein we report a new general method for one-step synthesis of four kinds of fluoroiodane(Ⅲ) reagents by treating the corresponding aryl iodides with silver difluoride (AgF2). This is the first method applicable for the synthesis of all four fluoroiodane(Ⅲ) reagents including p-iodotoluene difluoride (1), fluoro-benziodoxole (2), fluoro-benziodoxolone (3), and fluoro-N-acetylbenziodazole (4). AgF2 was firstly employed in the direct oxidative fluorination of iodobenzene and thus has shown its outstanding oxidation and fluorine-transfer ability. The use of AgF2 has improved the synthesis of fluoroiodane(Ⅲ) reagents by shortening the reaction steps, avoiding the use of hazardous reagents, and simplifying the experimental operations. It was worth noting that we have developed the first one-step direct synthetic method for 3, while 3 can only be synthesized through Cl→F ligand exchange reaction previously.
Intravenous nanosuspensions are attracted growing attention as a viable strategy for development of intravenous formulations of poorly water-soluble drugs. However, only few information about the biological fate of intravenous nanosuspensions is currently known, especially amorphous nanosuspensions are not reported yet. In this study, the in vivo fate of herpetrione (HPE) amorphous nanosuspensions following intravenous administration was explored by using an aggregation-caused quenching (ACQ) probe and HPLC methods. The ACQ probe is physically embedded into HPE nanoparticles via anti-solvent method to form HPE hybrid nanosuspensions (HPE-HNSs) for bioimaging. HPE-HNSs emit strong and stable fluorescence, but fluorescence quenches immediately upon the dissolution of HPE-HNSs, confirming the self-discrimination of HPE-HNSs. Following intravenous administration of HPE-HNSs, integral HPE-HNSs and HPE show similar degradation and biodistribution, with rapid clearance from blood circulation and obvious accumulation in liver and lung. Due to the slower dissolution and enhanced recognition by reticulo-endothelial system, 450 nm HPE-HNSs accumulate more in liver, lung and spleen than that of 200 nm HPE-HNSs. These results demonstrate that integral HPE-HNSs determine the in vivo performance of HPE-HNSs. This study provides insight into the in vivo fate of intravenous amorphous nanosuspensions.
An efficient and catalytic protocol for highly stereoselective construction of β-mannopyranosylation has been developed. Glycosylation of 2,6-lactone-bridged mannopyranosyl ortho-hexynylbenzoate with various acceptors proceeded smoothly in the presence of 5% Hg(Ⅱ) at room temperature, resulting in the corresponding β-mannosides in high yield and exclusive β-stereoselectivity.
Wastewater treatment and reclamation from wastewater are essential for the sustainable use of water resource. Zeolite-based heterogeneous catalysis shows great potential in circumventing the current limitations on pollutant removal and transformation to useful chemicals, inspiring advancements towards practical water treatment. This paper summarizes the methods for synthesizing zeolite-based catalyst, and the corresponding advantages and disadvantages. In comparison with traditional Fenton-like reaction, the superiority of zeolite-based catalysis lies in less sludge, wide pH range and easy recyclability. Accordingly, applications of zeolite-based Fenton-like catalysis (ZFCs) in pollutant removal and reclamation of wastewater were reviewed. Emphasis was placed on the methodological strategies in improving ZFCs, including the combination of external driving force (e.g., photocatalysis or electrochemistry), as well as the introduction of various transition metals into zeolite-based catalyst. Possible challenges and future perspectives for ZFCs were proposed.
A palladium-catalyzed formal [2 + 2 + 1] cyclization of 1-alkynyl-8-iodonaphthalene with double isocyanides is developed herein. The transformation worked well to produce a series of 7H-acenaphtho[1,2-b]pyrrole with a broad reaction scope. Isocyanides play a dual role in the reaction. One is a C1 building block, and another is used as C1N1 component. In the process, the [2 + 2 + 1] cyclization involves imidoylation, regioselective addition of imidoylpalladium species into alkyne, double imidoylation, and another addition of the resulting imidoylpalladium species into imine bonds.
α, β-Unsaturated primary amides are important intermediates and building blocks in organic synthesis. Herein, we report a ligand-free iron-catalyzed hydroaminocarbonylation of alkynes using NH4HCO3 as the ammonia source, enabling the highly efficient and regioselective synthesis of linear α, β-unsaturated primary amides. Various aromatic and aliphatic alkynes are transformed into the desired linear α, β-unsaturated primary amides in good to excellent yields. Further studies show that using NH4HCO3 as the ammonia source is key to obtain good yields and selectivity. The utility of this route is demonstrated with the synthesis of linear α, β-unsaturated amides including vanilloid receptor-1 antagonist TRPV-1.
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