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.
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.
A visible-light-mediated reaction of indole derivatives employing arylsulfonyl chlorides as sulfonyl surrogates has been developed, which proceeds via the sequence of reduction of sulfonyl chloride, sulfonylation, and intramolecular cyclization. This mild protocol transforms a diverse array of indole tethered alkenes and simple sulfonyl chlorides into highly valuable functionalized tetrahydrocarbazoles in good yields. This reaction is also suitable for gram-scale synthesis, which provides an efficient and green access to multi-substituted tetrahydrocarbazoles.
A new method for the preparation of fluoroalkylthioethers including trifluoromethylthioether and difluoromethylthioether by iridium(Ⅰ)-catalyzed deoxgenation of fluoroalkylsulfoxides with dimethyl diazomalonate was developed. In the reaction system, dimethyl diazomalonate was used as reducing reagent and the corresponding fluoroalkylthioethers were produced through oxygen atom transfer from fluoroalkylsulfoxides to diazomalonate. The protocol featuring effective oxygen atom transfer, mild reaction conditions and good functional groups tolerance offers an alternative strategy for the synthesis of fluoroalkylthioethers.
Herein, we adopt a simple supramolecular strategy to effectively control the tautomerism of ureidopyrimidinone (UPy) moiety and ultimately realize the complete arrangement of enol configuration. The obtained UPy derivatives containing self-complementary quadruple hydrogen bonding interactions can spontaneously self-assemble towards the formation of well-controlled, self-organized supramolecular nanostructure morphologies in both chloroform and water. The resulting aggregates had been fully characterized by various spectroscopy (absorption, emission) and microscopy (TEM, SEM and AFM) studies. It is anticipated that this study can provide an exact and excellent monomeric unit for controllable and precise supramolecular polymerization. The results achieved here also demonstrate the utility and feasibility of multiple hydrogen bonds to direct the self-assembly of small-molecule building blocks in aqueous media, which provides a strategy for the construction of well-defined and stable supramolecular architectures with chemical functionalities and physical properties as advanced materials for biological applications.
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.
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.
MIL-101(Fe)-NH2@Al2O3 (MA) catalysts were successfully synthesized by reactive seeding (RS) method on α-Al2O3 substrate, which demonstrated excellent photo-Fenton degradation performance toward fluoroquinolone antibiotics (i.e., norfloxacin, ciprofloxacin, and enrofloxacin). The structure and morphology of the obtained MA were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), atomic force microscope (AFM). The as-prepared MA could accomplish > 90% of norfloxacin degradation efficiency for 10 cycles' photo-Fenton processes, owing to its excellent chemical and water stability. In addition, the effects of operational factors including H2O2 concentration, foreign ions, and pH on the photo-Fenton degradation of norfloxacin over MA were clarified. The ESR spectra further document that •O2−, 1O2 and •OH radicals are prominent in the decomposition process of antibiotic molecules. Finally, the plausible photo-Fenton norfloxacin degradation mechanisms were proposed and verified.
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.
In this study, a method was developed to form C(sp3)–C(sp2) bonds via copper catalyst-promoted cross coupling of 2-methylquinoline and in-situ-activated 3-haloisoquinoline under mild conditions. The multi-component tandem reaction was used to construct new C–N, C=O and C–C bonds in one pot via sequential functionalization of the N1, C3 and C1 positions of 3-haloisoquinoline. This method can be used to efficiently access 1,2-disubstituted isoquinolinones by the three-component reaction of 3-halogen isoquinoline, alkyl halide, and 2-methylquinoline.
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