DMMIC derivatization-assisted liquid chromatography-mass spectrometry method for metabolite profiling of the glutathione anabolic pathway in esophageal cancer tissues and cells

In this work,a new pyrylium derivatization-assisted liquid chromatography-mass spectrometry(LC-MS)method was developed for metabolite profiling of the glutathione anabolic pathway(GAP)in cancer tissues and cells.The pyrylium salt of 6,7-dimethoxy-3-methyl isochromenylium tetrafluoroborate(DMMIC)was used to label the amino group of metabolites,and a reductant of dithiothreitol(DTT)was employed to stabilize the thiol group.By combining DMMIC derivatization with LC-MS,it was feasible to quantify the 13 main metabolites on the GAP in complex biological samples,which had good linearity(R^(2)=0.99810.9999),precision(interday precision of 1.6%e19.0%and intraday precision of 1.4%e19.8%)and accuracy(83.4%-115.7%).Moreover,the recovery assessments in tissues(82.5%e107.3%)and in cells(98.1%e118.9%)with GSH-^(13)C2,^(15)N,and Cys-^(15)N demonstrated the reliability of the method in detecting tissues and cells.Following a methodological evaluation,the method was applied successfully to investigate difference in the GAP between the carcinoma and para-carcinoma tissues of esophageal squamous cell carcinoma(ESCC)and the effect of p-hydroxycinnamaldehyde(CMSP)on the GAP in KYSE150 esophageal cancer cells.The results demonstrate that the developed method provides a promising new tool to elucidate the roles of GAP in physiological and pathological processes,which can contribute to research on drugs and diseases.

Synthesis of a glucose conjugate of pristimerin and evaluation of its anticancer activity

Taking advantage of the Warburg effect in cancer cells, glucose conjugation has emerged as a useful strategy for targeted delivery of anticancer agents. Pristimerin is a naturally occurring triterpenoid that displays potent but non-selective cytotoxicity. We developed a convergent and modular approach to construction of glucose-payload conjugates featuring copper-mediated azide-alkyne cycloaddition and prepared a glucose conjugate of pristimerin through this approach. The anticancer activity of this conjugate was evaluated in cancer cells and normal cells;however, the selectivity toward cancer cells was not significantly improved. We then examined the extracellular stability of the conjugate and found that its ester linkage was cleaved rapidly in Dulbecco’s Modified Eagle’s Medium at 37 °C, which resulted in the release of pristimerin. In fact, the inorganic components in this medium were sufficient to induce the cleavage.Given that the subtle difference between intrinsic stability and extracellular stability of the conjugate linker is often underappreciated, this work highlights the importance of the latter in the development of target-selective conjugates.

Two-thiols-regulated fabrication of plasmonic nanoparticles with co-enhanced Raman scattering and circular dichroism responses

Plasmonicnanoparticles(PNPs)with stable nanogaps are important to achieve strong,uniform and quantitative gap-enhanced Raman scattering(GERS)signals.Chiral PNPs with plasmonic circular dichroism(PCD)responses have been discovered to be suitable for applications in enantiomeric recognition,cancer therapy and activation of immune system.Herein,two-thiolsmodulated growth was demonstrated to result in the acquisition of PNPs with synergistically enhanced GERS and PCD signals.4-Aminothiophenol(4-ATP)and cysteine(Cys)played the role of Raman reporter and chiral stimulus,respectively.At a fixed 4-ATP concentration,the GERS signal of PNPs was significantly enhanced with the increase of the concentration of Cys.Simultaneously,at a fixed concentration of Cys,an increase in PCD response was observed by elevating the concentration of 4-ATP.Both aforementioned molecules acted as morphology controllers,leading to the formation of helical shell.It is suggested that the giant GERS and PCD response were contributed by the‘‘hot spots''within the PNPs and more perfect helical shells.Our research pointed out a novel synthetic guideline to obtain PNPs with multiple functionalities by incorporating multi-ligands into the growth stages.

Discovery of the anti-angiogenesis effect of eltrombopag in breast cancer through targeting of HuR protein

HuR(human antigen R), an mRNA-binding protein responsible for poor prognosis in nearly all kinds of malignancies, is a potential anti-tumor target for drug development. While screening HuR inhibitors with a fluorescence polarization(FP) based high-throughput screening(HTS) system, the clinically used drug eltrombopag was identified. Activity of eltrombopag on molecular level was verified with FP, electrophoretic mobility shift assay(EMSA), simulation docking and surface plasmon resonance(SPR). Further, we showed that eltrombopag inhibited in vitro cell proliferation of multiple cancer cell lines and macrophages, and the in vivo anti-tumor activity was also demonstrated in a 4T1 tumor-bearing mouse model. The in vivo data showed that eltrombopag was efficient in reducing microvessels in tumor tissues. We then confirmed the HuR-dependent anti-angiogenesis effect of eltrombopag in 4T1 cells and RAW264.7 macrophages with qRT-PCR, HuR-overexpression and HuR-silencing assays, RNA stability assays, RNA immunoprecipitation and luciferase assays. Finally, we analyzed the in vitro anti-angiogenesis effect of eltrombopag on human umbilical vein endothelial cells(HUVECs) mediated by macrophages with cell scratch assay and in vitro Matrigel angiogenesis assay. With these data, we revealed the HuR-dependent anti-angiogenesis effect of eltrombopag in breast tumor, suggesting that the existing drug eltrombopag may be used as an anti-cancer drug.

Highly Stereoselective Synthesis of 2,2-Disubstituted Vinylphosphonates via Aryl to Vinyl 1,4-Palladium Migration

Vinylphosphates play an important role in the fields of synthetic chemistry,pharmaceuticals and material science.It is a long-standing challenge to control the geometry of multi-substituted vinylphosphates.Herein,an efficient method for the synthesis of 2,2-disubstituted vinylphosphonates has been reported.The reaction proceeded via aryl to vinyl 1,4-palladium migration progress,in which two difficulties that the deactivation of palladium catalyst by the coordination of excess secondary phosphine oxide and the competitive cross-coupling to form arylphosphonates are successfully overcome.The judicious selection of phosphine ligand is the key to success.This protocol features excellent regio-and stereoselectivitiy,generally excellent reaction yields and broad substrate socpe.

Deciphering the Origin and Formation of Aminopyrrole Moiety in Kosinostatin Biosynthesis

Kosinostatin(KST)contains an uncommon aminopyrrole moiety,whose biosynthesis has remained elusive.Herein,aminopyrrolinic acid,which was generated by an L-ectoine synthase-like enzyme KstB3 via cyclization of L-glutamine,was identified to be the real substrate of adenylation enzyme KstB1.Subsequently,a FAD-dependent dehydrogenase KstB4 along with a transglutaminase-like enzyme KstB6 were also involved in formation of aminopyrrole.These results provided an unusual pathway for 2-aminopyrrole formation in KST biosynthesis.

An Unconventional trans-exo-Selective Cyclization of Alkyne-Tethered Cyclohexadienones Initiated by Rhodium(III)-Catalyzed C-H Activation via Insertion Relay

Different from the established trans-endo-selective cyclization of alkyne-tethered electrophiles that involve an E/Z isomerization process,herein,the authors present a novel strategy to allow trans-exo-selective arylative cyclization of 1,6-enynes.Through initiation of rhodium(III)-catalyzed C-H activation,a diverse range of N-heterocyclic directing groups,including pyridine,pyrazole,imidazo[1,2-a]pyridine,benzoxazole,benzothiazole,and purine,was feasible for the cascade transformation,exhibiting high efficiency(up to 92%yield),broad substrate scope,and excellent functional group compatibility.Moreover,the modification of natural products and pharmaceutical compounds was also demonstrated to showcase its synthetic utility.Based on density functional theory(DFT)calculations,a key three-membered ring intermediate through the insertion relay,rather than the direct E/Z isomerization of alkenyl rhodium species,controlled the stereochemical outcome for this trans-exo-selective cyclization.The subsequent ring-opening protonation of the more favored rotamer led to exclusive trans-exo-selectivity.

A parallel approach to direct resolution of albuterol

A library consisting of a series of O,O'-diaryzoyl-L-(-)-tartaric acids (2) was designed and synthesized. The substituent on the aromatic ring of 2 significantly affects the diastereomeric excess and efficiency of the resolution of racemic albuterol (1). Excel-lent resolving reagent 2a was selected for the resolution of rac-1 via the parallel approach. However,a family of three resolving reagents failed to improve the resolution efficiency of rac-1.

DBU-catalyzed dearomative annulation of 2-pyridylacetates withα,β-unsaturated pyrazolamides for the synthesis of multisubstituted 2,3-dihydro-4H-quinolizin-4-ones

The reaction of 2-pyridylacetates andα,β-unsaturated pyrazolamides with DBU as the catalyst has been developed.A range of unexplored multisubstituted 2,3-dihydro-4H-quinolizin-4-ones are obtained with satisfactory yields(up to 94%)and excellent diastereoselectivities(all cases>20:1 dr)via a dearomative[3+3]annulation process.This practical method also features transition metal free,mild reaction conditions,wide functional group tolerance,easy scale-up synthesis,and versatile further derivatization.

Chloride anion-induced dimer capsule based on a polyfluorinated macrocycle meta-WreathArene

[1_n]metacyclophanes are a class of important building blocks for supramolecular assembly of artificial capsules. Herein we present the preparation and properties of a novel polyfluorinated macrocycle metaWreath Arene, a C_(2)-symmetrical [14]metacyclophane. Adopting a cone conformation in acetone solution,the macrocycle can form dimer capsules through hydrogen bonds induced by chloride anions. Each dimer capsule consists of two meta-Wreath Arene and two chloride anions, and has been unambiguously characterized both in solution and in solid state.

Aggregation-enabled alkene insertion into carbon–halogen bonds

Molecular aggregation affects the electronic interactions between molecules and has emerged as a powerful tool in material science.Aggregate effect finds wide applications in the research of new physical phenomena;however,its value for chemical reaction development has been far less explored.Herein,we report the development of aggregation-enabled alkene insertion into carbon–halogen bonds.The spontaneous cleavage of C–X(X=Cl,Br,or I)bonds generates an intimate ion pair,which can be quickly captured by alkenes in an aggregated state.Additional catalysts or promoters are not necessary under such circumstances,and solvent quenching experiments indicate that the aggregated state is critical for achieving such sequences.The ionic insertion mode is supported by mechanistic studies,density functional theory calculations,and symmetry-adapted perturbation theory analysis.Results also show that the non-aggregated state may quench the transition state and terminate the insertion process.