Latest ArticlesPyrroles are important structural units of natural products, drug molecules, biomolecules and functional material molecules. Efficient synthesis of α-functionalized pyrroles with different substituents from easily accessible starting materials is still challenging. Herein, a facile and regioselective coarctate reaction of enynals involving a free carbene intermediate has been developed, which allows the divergent and practical de novo synthesis of various α-furanyl pyrroles and α-cyclopropenyl pyrroles derivatives with good to excellent yields and high efficiency under mild conditions. This approach features readily accessible starting materials, high functional group compatibility, step economy and scalability, which would complement previous methods and support expansion of the toolbox for the synthesis of valuable, but previously inaccessible, highly substituted and electron-rich α-functionalized pyrroles.
Two lindenane-type sesquiterpene (LDS) trimers with unprecedented carbon skeletons, holotrichones A (1) and B (2), were obtained from the whole plant of Chloranthus holostegius var. trichoneurus by a ultra performance liquid chromatography-photodiode array detector-mass spectrometry (UPLC-PDA-MS)-guided isolation strategy. Compound 1 represents the first LDS trimer incorporating a unique 3/5/6/6-fused framework, in which a lindenane-type monomer and the 2-methylbutyryl substituent of an LDS dimer is bridged by a six-membered ring system. Compound 2 is the first hetero-trimer fused by an LDS dimer with a p-benzoquinone-meroterpenoid, featuring an unusual 3/5/6/6/3/5/6/6/6 nonacyclic system fused by the sesquiterpenoid unit and a 2-geranyl-6-methyl-2,5-cyclohexadien-1,4-dione moiety. In compound 2, the dimeric LDS moiety is equipped with a rare oxaspiro[4.5]decane system. Their structures, including absolute configurations, were established by spectroscopic methods, GIAO NMR calculations and DP4+ probability analyses, electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction analysis. The plausible biogenetic pathway speculation indicated that hetero- and homo-Diels-Alder additions may dominate the formation of these highly fused polycyclic frameworks. Both compounds 1 and 2 induced the human acute myeloid leukemia MV-4–11 cell death via apoptosis induction, which deserves further investigation on this new chemical class of LDS oligomers for their anti-leukemic potential.
Increasing interests of difluorinated amino acids (DFAAs) have been raised in recent years due to their widespread bio-organic and medical applications. However, to date, only few investigations focused on their asymmetric synthesis. Exploring difluoromethyl reagent to tailor a novel pathway and developing efficient catalytic system are highly desirable for constructing structurally diverse chiral DFAAs. Herein, a copper-catalyzed asymmetric difluorobenzylation of aldimine esters is described. By using α,α-difluorinated benzyltriflones as difluoromethyl reagents, this protocol allows the asymmetric synthesis of α-quaternary DFAAs with wide scope, good yields and excellent enantioselectivities (90%-98% ee). Control experiments and DESI-MS analysis demonstrate the reaction probably proceeds via a key difluorocarbocation intermediate. Moreover, polyfluoroarenes are found efficient candidates to polyfluoroaryl amino acids via C-F activation. Gram-scale experiment, late-stage functionalization, synthesis of difluorinated dipeptides and bioactive molecular analogues revealed the utility of the protocol, thereby largely enriching the structural diversity of FAAs and providing more potential opportunities in drug discovery.
Lymphoma is a hematological malignancy with an increasing mortality rate. Nevertheless, the treatment strategy against lymphoma remains limited. Doxorubicin (DOX) is a broad-spectrum anti-tumor chemotherapeutic drug, the clinical application of which is limited by serious adverse effects and drug resistance. In this work, biodegradable methoxy poly(ethylene glycol)-block-poly(lactic acid) (mPEG-PLA) nanomicelles co-delivering of DOX and apatinib (AP) (DOX-AP/m) was developed for lymphoma therapy. The average particle size of the self-assembled drug-loaded nano-micelle was 31.94 nm. It is revealed that AP can enhance the uptake of DOX by tumor cells. The in vivo and in vitro experimental results revealed that DOX-AP/m combination therapy could inhibit proliferation and promote apoptosis of lymphoma cells, and greatly suppress tumor growth. Our study indicated that DOX-AP/m might provide new insight and hold great potential in the treatment of lymphoma.
To efficiently remove perfluorooctanoic acid (PFOA), we developed a composite of magnetic Fe3O4 nanocrystals and MIL-101 (an iron-based metal organic framework). Because of its high surface area, porous structure, and complexation between PFOA as confirmed by experimental results and density functional theory simulation, the magnetic composite showed a Langmuir adsorption capacity of 415 mg/g in the presence of various groundwater components, and thus adsorbed PFOA at environment-relevant concentration within 20 min. The catalyst loaded with PFOA can then be magnetically separated from the synthetic groundwater. This adsorption step concentrated PFOA near MIL-101 and resulted in a fast decomposition rate in the decomposition step, where MIL-101 served as an efficient Fenton agent due to its abundant Fe3+/Fe2+ sites. Meanwhile, the alternative magnetic field was introduced to change the production pathway of reactive oxygen species and superoxide radical anions were produced, which was critical for PFOA degradation. In addition, the inductive heating effect heat the magnetic particles to 445 K through an in-situ approach, which thus further accelerated Fenton reactions rate. In addition, and achieved a complete degradation of PFOA within 30 min. This newly developed Fenton catalyst demonstrates advantages over conventionally heterogeneous and homogeneous catalysts, and thus is promising for practical applications.
Osteoporosis is a disease of bone metabolism homeostasis imbalance with obvious bone loss, damage to bone microstructure, and increased risk of fracture. The occurrence and development of osteoporosis is related to the augmentation of active osteoclasts. Receptor activator of nuclear factor kappa B (RANK) small interfering RNA (siRNA) knockdowns the expression of RANK mRNA to inhibit the osteoclast precursors differentiate into osteoclasts as a treatment in osteoporosis. Salmon calcitonin (sCT) is a commonly used anti-osteoporotic agent that inhibits osteoclast activity and induces osteoclast apoptosis, and it also could promote the osteogenesis by osteoblasts. A cocktail therapy improves the therapeutic effect of osteoporosis between RANK siRNA and sCT. A size-switchable microsphere from micro to nano scale was developed to address the delivery barriers of biomacromolecules with poor stability and frequent administration. RANK siRNA and sCT were incorporated into the microspheres with a nanoparticle/micelle-microsphere double-layer structure to achieve sustained release when the particle size shrunk and dual protection of RANK siRNA and sCT. The size-switchable microspheres MS@(AL-NPs/ARM) had an optimal therapeutic effect and reduced the frequency of administration in glucocorticoid induced osteoporosis (GIOP) mouse model. RANK siRNA and sCT co-delivery system based on size-switchable microsphere is a promising strategy to treat osteoporosis through the controlled release of biomacromolecules.
The chemical investigation into the EtOAc extract of the deep-sea-derived fungus Penicillium citrinum W22 yielded three unprecedented citrinin dimers, neo-Dicitrinols A–C (1–3) and a known one, penicitrinone A (4). Their structures were elucidated by extensive analysis of spectroscopic data, electronic circular dichroism (ECD) calculation, X-ray diffraction, and biogenetic consideration. neo-Dicitrinols A–C (1–3), bearing a tetramic acid unit, represent the first example of citrinin analogues as hybrid polyketide synthase-nonribosomal peptide synthase (PKS-NRPS) products. neo-Dicitrinol C (3) significantly inhibited renin-angiotensin system-selective lethal 3 (RSL3)-induced ferroptosis with a half maximal effective concentration (EC50) value of 21.6 µmol/L.
Owing to the high spatiotemporal resolution, the second near-infrared (NIR-Ⅱ) imaging window can provide high imaging contrast with diminished tissue autofluorescence and suppressed photon scattering to pinpoint the locations for tumor surgery. Due to the unique optical properties and excellent fluorescence performance, quantum dots (QDs) are regarded as ideal nanoprobes for fluorescence-guided surgery (FGS). Moreover, QDs can be excited by a variety of light sources owing to the continuous and wide absorption ranges. Herein, light-emitting diode (LED) was used as the excitation source of QDs-based nanoprobes to realize FGS of tumor with high resolution. Since the LED light could irradiate a large region with consistent light intensity, signal distortion at the edge of imaging field was avoided. The signal intensity of the view edges under LED excitation can be improved by about 5 times compared to laser excitation. Therefore, more micro-vessels and smaller tumors (Vtumor < 5 mm2) could be detected, thus providing more precise guidance for tumor resection surgery.
Sonodynamic therapy (SDT) exhibits noninvasive and accuracy in cancer treatment, and has aroused widespread attention. However, the low quantum yield of inorganic sonosensitizers under ultrasound (US) stimulation leads to unsatisfactory efficacy. In this work, an urchin-like piezoelectric ZnSnO3/Cu3P p-n heterojunction was constructed as an efficient sonosensitizer for enhanced SDT. The p-n heterojunction formation narrows the band bandgap and increases the piezoelectric property, which contribute to the promotion of carrier separation and suppression of carrier recombination, resulting in enhanced SDT. Moreover, under tumor microenvironment (TME) with over produced H2O2 and glutathione (GSH), Cu3P NNs induce chemodynamic therapy (CDT) by initiating a Fenton-like reaction and depleting GSH, leading to increased cellular oxidative damage. With the combination effect, the ZnSnO3/Cu3P heterojunction demonstrates a 70% tumor growth inhibition rate in 4T1 tumor mice model. This piezoelectric heterojunction achieves the combined treatment of SDT and CDT, and opens new possibilities for the application of SDT in tumor therapy.
Two o-carborane based tetraphenylethene (TPE) cationic cyclophanes O1·4PF6 and O2·4PF6 were synthesized through an SN2 reaction. Their structures were confirmed both possessing Z-shaped cavities in single crystal analysis. The optical properties of these macrocycles were systematically investigated using UV–vis spectroscopy and fluorescence techniques. It is worth noting that the introduction of a methoxy group to the TPE unit enables the synthesis of a near-infrared-emitting macrocycle O2·4PF6. The recognition behaviors of these two macrocycles towards nucleotides were investigated using various techniques including fluorescence titration, UV–vis titration, and transmission electron microscopy (TEM). Interestingly, these cyclophanes exhibited aggregation-induced emission (AIE) effects in water or under the induction of nucleotides.
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