The switchable cross-coupling of indoles and pyridotriazoles through carbene insertion at C_(2)-or C_(3)-positon has been developed in this paper.This highly site-selective C-H carbenoid functionalization is determine...The switchable cross-coupling of indoles and pyridotriazoles through carbene insertion at C_(2)-or C_(3)-positon has been developed in this paper.This highly site-selective C-H carbenoid functionalization is determined by both the Rh-catalyst species and auxiliary groups.[Cp∗RhCl_(2)]_(2) and coordinating pyrimidyl group direct the C-H carbenoid functionalization to occur at the C_(2)-position,while Rh2OAc4 and noncoordinating benzyl group lead the reaction to occur at the C_(3)-position of the indoles.This regioselective C−H functionalization strategy is of significant importance for the discovery of indole drugs.展开更多
Chemical modification of native peptides and proteins is a versatile strategy to facilitate late-stage diversification for functional studies.Among the proteogenic amino acids,lysine is extensively involved in posttra...Chemical modification of native peptides and proteins is a versatile strategy to facilitate late-stage diversification for functional studies.Among the proteogenic amino acids,lysine is extensively involved in posttranslational modifications and the binding of ligands to target proteins,making its selective modification attractive.However,lysine’s high natural abundance and solvent accessibility,as well as its relatively low reactivity to cysteine,necessitate addressing chemoselectivity and regioselectivity for the Lys modification of native proteins.Although Lys chemoselective modification methods have been well developed,achieving site-selective modification of a specific Lys residue remains a great challenge.In this review,we discussed the challenges of Lys selective modification,presented recent examples of Lys chemoselective modification,and summarized the currently known methods and strategies for Lys site-selective modification.We also included an outlook on potential solutions for Lys site-selective labeling and its potential applications in chemical biology and drug development.展开更多
Reader proteins that bind specific methyllysine are important to biological functions of lysine methylation,but readers of many methyllysine sites are still unknown.Therefore,development of covalent probes is importan...Reader proteins that bind specific methyllysine are important to biological functions of lysine methylation,but readers of many methyllysine sites are still unknown.Therefore,development of covalent probes is important to identify readers from cell samples so as to understand biological roles of lysine methylation.Generally,readers bind methyllysine via aromatic cages that contain tryptophan,tyrosine and phenylalanine,that offer a unique motif for selective crosslinking.We recently reported a site-selective tryptophan crosslinking strategy based on dimethylsulfonium that mimics dimethyllysine to crosslink tryptophan in aromatic cages of readers.Since tyrosine is a key residue for binding affinity to methyllysine,especially some readers that do not contain tryptophan residues in the binding pocket.Here we developed strategies of site-selective crosslinking to tyrosine.Ultraviolet(UV)source was applied to excite tyrosine at neutral pH or phenoxide at basic p H,and subsequent single-electron transfer(SET)from Tyr*to sulfonium inside the binding pocket enables selective crosslinking.In consequence,methyllysine readers with tyrosine-containing aromatic cages could be selectively crosslinked by site-specific sulfonium peptide probes.In addition,we expanded substrates from aromatic cages to tyrosine residues of proximate contact with sulfonium probes.The pair of LgBiT and SmBiT exhibited orthogonal crosslinking in complicated cell samples.As a result,we may expand sulfonium tools to target local tyrosine in future investigations.展开更多
A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymale...A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymaleimide(NHMI),serves as a hydrogen atom-transfer mediator.Good-to-excellent site selectivity was observed among different substrates,providing a practical approach for site-selective benzylic C–H oxidation.Additionally,the hydrogen-atom transfer mechanism for C–H electrochemical oxidation allows the oxidation to proceed at much lower anode potentials relative to direct electrolysis and with minimal reliance on the substrate's electronic properties.展开更多
Late-stage modification of complex molecules via site-selective hydrodefluorination is a challenging endeavor.The selective activation of carbon-fluorine(C-F) bonds in the presence of multiple C-F bonds is of importan...Late-stage modification of complex molecules via site-selective hydrodefluorination is a challenging endeavor.The selective activation of carbon-fluorine(C-F) bonds in the presence of multiple C-F bonds is of importance in organic synthesis and drug discovery.Herein,we describe the activation of C-F bonds via multiphoton photoredox catalysis to selectively produces a series of hydrodefluorinated compounds by simply tuning the reaction conditions.Moreover,this protocol was successfully applied to the late-stage functionalization of different drug-derivatives and the corresponding mono-,di-,and tri-defluorinated products were obtained in good to excellent yields.A detailed mechanistic investigation provides insight into the unprecedented hydrodefluorination pathway.展开更多
A rhodium-catalyzed directing group promoted selective C-H olefination reaction of indolizines at the 8-position is re ported.Di-olefination at 2,8-positions also achieved with silver hexafluoroantimonate as an additi...A rhodium-catalyzed directing group promoted selective C-H olefination reaction of indolizines at the 8-position is re ported.Di-olefination at 2,8-positions also achieved with silver hexafluoroantimonate as an additive under similar reaction conditions.Weakly coordinating groups,such as ketone,alde hyde,amide and ester,were used as directing groups.The ester group can be removed under acid conditions and therefore is used as a traceless directing group.展开更多
The electronic structure of Eu-doped NaTaO3 in Na-rich environment is investigated by the first-principles theory. By simulating the two different models of Eu3＋ ions selectively located in Ta and Na sites, respectiv...The electronic structure of Eu-doped NaTaO3 in Na-rich environment is investigated by the first-principles theory. By simulating the two different models of Eu3＋ ions selectively located in Ta and Na sites, respectively, the band gaps of two Eu-doped NaTaO3 models were all narrowed, which were assigned to lattice defects and impurity band of the Eu dopent. For the model of Eu3＋ ions located in the Na＋ sites of NaTaO3, the new impurity band mainly composited of Eu 4f orbital appeared at the top over the valence band, indicating the enhanced oxidative ability. For the model of Eu3＋ ions located in the Ta5＋ sites of NaTaO3, a midgap state generated was located at the bottom of conduct band and the band potential shifted up, confirming the strong reductive ability in the Na-rich enviornment. The densities of electron states were significantly increased in both the conduction and valence bands in Na-rich model, which resulted in the increased carrier migration rate and thus photocatalytic activity enhancement. It is proposed that Eu3＋ ions doping at the Ta sites could enhance the reduced photocatalytic performance via controlling the nonstoichiometric Na/Ta molar ratio in the Eu-doped NaTaO3 system.展开更多
Transition-metal-catalyzed remote sp^(2)C-H functionalization of aryl sulfonic acids was hardly ever real-ized owing to competitive ortho-C-H functionalization of aryl sulfonates and electron-deficient nature of pheny...Transition-metal-catalyzed remote sp^(2)C-H functionalization of aryl sulfonic acids was hardly ever real-ized owing to competitive ortho-C-H functionalization of aryl sulfonates and electron-deficient nature of phenyl ring.Herein,with the assistance of a practical biaryl indolyl directing template,palladium-catalyzed remote sp^(2)C-H alkylation of aryl sulfonic acids have been achieved in moderate to good yields with exclusive meta selectivity.Moreover,remote meta-selective C-H alkynylation of aryl sulfonic acids was also accomplished with a rhodium catalyst.These meta-C-H functionalized products proved to be the superior synthetic precursors,which are difficult to access using the conventional strategy.展开更多
We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculati...We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculation.It is found that the 5f electronic correlations inβ-uranium are moderate.More interestingly,their strengths are site selective,depending on the local atomic environment of the present uranium atom.As a consequence,the occupation matrices and partial 5f density of states ofβ-uranium manifest site dependence.In addition,the complicate experimental structure ofβ-uranium could be well reproduced within this theoretical framework.展开更多
Ordered zinc oxide （ZnO） rod arrays with very high orientation were fabricated on Si substrates by using a solution method. The substrate surfaces were functionalized by Self-Assembly Monolayers （SAMs）. In the ver...Ordered zinc oxide （ZnO） rod arrays with very high orientation were fabricated on Si substrates by using a solution method. The substrate surfaces were functionalized by Self-Assembly Monolayers （SAMs）. In the very early growth stage, the oriented ZnO crystals had already grown, which appeared to be the main reason why ZnO nanorods showed very high orientation. The un-dense and un-uniform SAMs provided a surface that was heterogeneous to ZnO nucleation. Consequently, highly oriented ZnO rods were selectively grown on the ＂coin-like＂ SAM-uncovered regions. The route developed here can provide some helpful information to control the nucleation and orientation of ZnO in aqueous solution. Also, the site-selective growth mechanisms can indicate a clue to grow patterned highly oriented ZnO nanorod arrays by the organic template.展开更多
The rare earth berate YBO3 synthesized by sol-gel technique was found to be in two phases. However, the low-svmmetry form of YBO3 which was found also in some other rare earth (Sm, Eu, Gd) berates has a much different...The rare earth berate YBO3 synthesized by sol-gel technique was found to be in two phases. However, the low-svmmetry form of YBO3 which was found also in some other rare earth (Sm, Eu, Gd) berates has a much different dependence on the preparing conditions, The photoluminescent spectra indicate that there are more than two sites for Eu3+ in the sol-gel prepared polycrystalline YBO3:Eu with low-symmetry.展开更多
Recent years have seen an ever increasing number of enzyme mediated protein/peptide modification reactions, which contribute significantly to the elucidation of related biological functions. The many available enzymes...Recent years have seen an ever increasing number of enzyme mediated protein/peptide modification reactions, which contribute significantly to the elucidation of related biological functions. The many available enzymes have, however, caused difficulties for practitioners in choosing the most appropriate enzyme for a certain purpose. This review surveyed the widely used enzymes(i.e., sortases, butelase 1,subtiligase, formylglycine generating enzyme and farnesyltransferase) in the manipulation of proteins/peptides, and the application fields of these enzymes as well as the advantages and limitations of each enzyme are summarized.展开更多
Controlled growth of islands on plasmonic metal nanoparticles represents a novel strategy in creating unique morphologies that are difficult to achieve by conventional colloidal synthesis processes,where the nanoparti...Controlled growth of islands on plasmonic metal nanoparticles represents a novel strategy in creating unique morphologies that are difficult to achieve by conventional colloidal synthesis processes,where the nanoparticle morphologies are typically determined by the preferential development of certain crystal facets.This work exploits an effective surface-engineering strategy for site-selective island growth of Au on anisotropic Au nanostructures.Selective ligand modification is first employed to direct the site-selective deposition of a thin transition layer of a secondary metal,e.g.,Pd,which has a considerable lattice mismatch with Au.The selective deposition of Pd on the original seeds produces a high contrast in the surface strain that guides the subsequent site-selective growth of Au islands.This strategy proves effective in not only inducing the island growth of Au on Au nanostructures but also manipulating the location of grown islands.By taking advantage of the iodide-assisted oxidative ripening process and the surface strain profile on Au nanostructures,we further demonstrate the precise control of the islands’number,coverage,and wetting degree,allowing fine-tuning of nanoparticles’optical properties.展开更多
Many of the commonly used pharmaceuticals and biologically active natural products are nitrogencontaining compounds.Recently,the transitionmetal-catalyzed or the radical-mediated 1,2-carboamination of alkenes has been...Many of the commonly used pharmaceuticals and biologically active natural products are nitrogencontaining compounds.Recently,the transitionmetal-catalyzed or the radical-mediated 1,2-carboamination of alkenes has been well explored to access amine scaffolds.However,synthetic strategies toward the 1,1-carboamination of alkenes are severely limited.Herein,we describe a method to achieve the 1,1-arylamination using readily available building blocks enabled by palladium catalysis.This sequential three step-Heck arylation,metal migration,followed by aza-1,6-Micheal addition process exhibits excellent chemo-and regioselectivity.To showcase the potential as a method for diversity-oriented drug discovery,the modification of numerous structurally complex bioactive molecules was also successfully performed.展开更多
Perovskite barium titanate(BaTiO3)demonstrates exceptional dielectric properties as a promising microwave-absorbing(MA)material.Leveraging structural flexibility of perovskites,magnetic components can be incorporated ...Perovskite barium titanate(BaTiO3)demonstrates exceptional dielectric properties as a promising microwave-absorbing(MA)material.Leveraging structural flexibility of perovskites,magnetic components can be incorporated at A/B-sites to enhance MA performance,yet the fundamental disparity in MA mechanisms between A/B-site magnetic doping remains elusive.Herein,nickel-doped BaTiO3 perovskites were systematically synthesized through precise adjustment of the Ba/Ti molar ratio to achieve both A-site(Ni_(x)Ba_(1−x)TiO_(3),N_(x)BTO)and B-site(BaTi_(1−x)Ni_(x)O_(3),BTN^(x)O)substitutions(0≤x≤0.1)via a simple one-step hydrothermal method.Notably,A-site Ni^(2+)substitution in N_(x)BTO induced superior magnetic loss(tanδμ=0.39)attributed to eddy-current dissipation,while B-site doping in BTN^(x)O achieved higher dielectric loss(tanδε=0.49).The N0.1BTO sample exhibited optimal MA performance with a remarkable minimum reflection loss(RLmin)of−44.39 dB and broad effective absorption bandwidth(EAB=8.66 GHz)covering the Ku-band and 67%X-band.Multimodal analysis revealed synergistic interactions among multiple reflection and scattering,multi-polarization relaxation,natural resonance,and eddy currents.In contrast,BTN0.01O demonstrated deeper RLmin(−50.88 dB)but narrower EAB(3.33 GHz)governed by dielectric mechanisms.Structural characterization indicated A-site doping induced lattice distortion,reduced unit-cell volume,and optimized oxygen vacancy distribution,synergistically balancing magneto-dielectric parameters.Conversely,B-site substitution increased oxygen vacancy concentration and carrier mobility while amplifying dielectric fluctuations.The spatial occupation preference of A/B dopants(A-site and B-site)governs lattice symmetry breaking,consequently establishing structure-property relationships and underpinning the material’s tunable dielectric behavior and magnetic phenomena.This work proposes a site-selective doping strategy for designing high-performance perovskite MA materials through magneto-dielectric equilibrium optimization.展开更多
The direct conversion of unactivated alkanes and cycloalkanes into structurally diverse molecules through aliphatic C—H functionalization is a useful process, which has attracted intense interest from academia and in...The direct conversion of unactivated alkanes and cycloalkanes into structurally diverse molecules through aliphatic C—H functionalization is a useful process, which has attracted intense interest from academia and industry. Methods to control chemo- and site-selectivity, combined with asymmetric catalysis, provide appealing access to high value-added enantiomer-enriched compounds but are far less developed. This review focuses on recent progress in (i) asymmetric reactions of alkanes or cycloalkanes with prochiral substrates which generate a stereocenter adjacent to the cleaved C(sp3)–H bond, and (ii) C(sp3)–H enantiodiscriminatory reactions creating a new stereogenic center on the carbon of a cleaved C(sp3)–H bond. Elegant strategies are discussed, including (a) metal carbene-induced C—H insertions by chiral rhodium catalysts, (b) metal-oxo-mediated C—H oxidation by biomimetic manganese catalysts, (c) enzyme catalysis by cytochromes P450 variants, and (d) dual catalysis by a photocatalyst and a chiral Lewis acid (CLA) or a chiral phosphoric acid (CPA). These catalytic systems can not only precisely recognize primary, secondary and tertiary C—H bonds at specific positions in alkanes and cycloalkanes, but also support a high level of stereoselectivity in the reactions. It is expected that the advances will stimulate further progress in asymmetric catalysis, synthetic methodology, pharmaceutical development and industrial processes.展开更多
A novel benzyl cation-triggered site-selective sp^(2) C—H phosphorylation and etherification was developed. This reaction was conducted under the transition metal-free conditions through cation migration via dearomat...A novel benzyl cation-triggered site-selective sp^(2) C—H phosphorylation and etherification was developed. This reaction was conducted under the transition metal-free conditions through cation migration via dearomatization. Under the reaction conditions, the derivatives of naphthalenes, benzofurans and benzo[b]thiophenes all can be transformed into the corresponding products in good to excellent yields. It provides a method to construct sp^(2) C—P and sp^(2) C—O bonds as well as a new strategy for benzylic activation-triggered sp^(2) C—H functionalization.展开更多
Rational design and construction of chiral-achiral hybrid structures are of great importance to realize the multifunctional complex chiral structures toward emerging technological applications. However, significant ch...Rational design and construction of chiral-achiral hybrid structures are of great importance to realize the multifunctional complex chiral structures toward emerging technological applications. However, significant challenges remain due to the lack of fine control over the heterostructure. Here, we have developed a general bottom-up synthetic strategy for the site-selective growth of Cu nanodomains on intrinsically chiral Au nanocrystals. Chiral AuCu heterostructures with three distinct architectures were achieved by controlling the overgrowth of Cu nanodomains in a site-specific manner. The geometry-dependent plasmonic chirality of the heterostructures was demonstrated experimentally by circular dichroism spectroscopy and theoretically through finite-difference time-domain simulations. The site-specific geometric control of chiral AuCu heterostructures was also extended to employ anisotropic chiral Au nanoplates and nanorods as the building blocks. By virtue of the galvanic replacement reactions between metal ions and Cu atoms, chiral heterostructures with increasing architectural complexity and compositional diversity can be further achieved. The current work not only opens up a promising strategy to synthesize complex chiral hybrid nanostructures but also provides an important knowledge framework that guides the rational design of multifunctional chiral hybrid nanostructures toward chiroptical applications.展开更多
A novel protocol for the preparation of highly functionalized 2-azabicyclo[3.3.1]nonane(morphan)derivatives via a multicomponent cascade reaction,involving 3-formylchromones,2-naphthols,and enaminones in the ionic liq...A novel protocol for the preparation of highly functionalized 2-azabicyclo[3.3.1]nonane(morphan)derivatives via a multicomponent cascade reaction,involving 3-formylchromones,2-naphthols,and enaminones in the ionic liquid[BMIM]PF6 as the solvent and promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU),was developed,which involved the cleavage of one C–O bond and formation of four bonds(1 C–O,1 C–N,and 2 C–C bonds).As a result,a series of morphan derivatives were produced through a cascade reaction,including a sequence of 1,2-addition,enol-keto tautomerization,Michael addition,dehydration,another Michael addition,imine-enamine tautomerization,and N-alkylation reactions,which were accompanied by a ring-opening reaction.This protocol was suitable for combinatorial and parallel syntheses of natural product-like morphan compounds in a one-pot reaction rather than through tedious multi-step reactions.展开更多
The development of a facile cysteine-directed S-glycosylation strategy would facilitate the intensive investigation of the effect of glycosylation on protein translational modification.Herein,we introduce glycosyl Bun...The development of a facile cysteine-directed S-glycosylation strategy would facilitate the intensive investigation of the effect of glycosylation on protein translational modification.Herein,we introduce glycosyl Bunte salt as an efficient glycosyl donor for site-selective peptide/protein modification.The coupling reaction with cysteine thiols under alkaline buffer conditions proceeded chemoselectively,delivering homogeneous glycoconjugates and inorganic salt as the only byproduct.A series of sugar moieties,including monosaccharides and oligosaccharides,were successfully conjugated to the peptides and protein via the disulfide bond.Furthermore,this protocol was applied to the glycosylation of the glucagon-like peptide 1(GLP-1)variant,and its glycosylated effect on blood glucose control was also studied.展开更多
基金CAMS Innovation Fund for Medical Sciences(CIFMS)(Nos.2022-I2M-1-013,2022-I2M-1-014,2022-I2M-2-002).
文摘The switchable cross-coupling of indoles and pyridotriazoles through carbene insertion at C_(2)-or C_(3)-positon has been developed in this paper.This highly site-selective C-H carbenoid functionalization is determined by both the Rh-catalyst species and auxiliary groups.[Cp∗RhCl_(2)]_(2) and coordinating pyrimidyl group direct the C-H carbenoid functionalization to occur at the C_(2)-position,while Rh2OAc4 and noncoordinating benzyl group lead the reaction to occur at the C_(3)-position of the indoles.This regioselective C−H functionalization strategy is of significant importance for the discovery of indole drugs.
基金the National Natural Science Foundation of China(Nos.82373722,22077144)Hunan Provincial Natural Science Foundation of China(No.2023JJ30527)+2 种基金Guangdong Basic and Applied Basic Research Foundation(No.2023B1515040006)Guangdong Provincial Key Laboratory of Construction Foundation(No.2023B1212060022)Key Research and Development Program of Guangdong Province(No.2020B1111110003).
文摘Chemical modification of native peptides and proteins is a versatile strategy to facilitate late-stage diversification for functional studies.Among the proteogenic amino acids,lysine is extensively involved in posttranslational modifications and the binding of ligands to target proteins,making its selective modification attractive.However,lysine’s high natural abundance and solvent accessibility,as well as its relatively low reactivity to cysteine,necessitate addressing chemoselectivity and regioselectivity for the Lys modification of native proteins.Although Lys chemoselective modification methods have been well developed,achieving site-selective modification of a specific Lys residue remains a great challenge.In this review,we discussed the challenges of Lys selective modification,presented recent examples of Lys chemoselective modification,and summarized the currently known methods and strategies for Lys site-selective modification.We also included an outlook on potential solutions for Lys site-selective labeling and its potential applications in chemical biology and drug development.
基金the support from National Natural Science Foundation of China(No.22161132006)Key R&D Program of Zhejiang(No.2024SSYS0036)Westlake University Startup。
文摘Reader proteins that bind specific methyllysine are important to biological functions of lysine methylation,but readers of many methyllysine sites are still unknown.Therefore,development of covalent probes is important to identify readers from cell samples so as to understand biological roles of lysine methylation.Generally,readers bind methyllysine via aromatic cages that contain tryptophan,tyrosine and phenylalanine,that offer a unique motif for selective crosslinking.We recently reported a site-selective tryptophan crosslinking strategy based on dimethylsulfonium that mimics dimethyllysine to crosslink tryptophan in aromatic cages of readers.Since tyrosine is a key residue for binding affinity to methyllysine,especially some readers that do not contain tryptophan residues in the binding pocket.Here we developed strategies of site-selective crosslinking to tyrosine.Ultraviolet(UV)source was applied to excite tyrosine at neutral pH or phenoxide at basic p H,and subsequent single-electron transfer(SET)from Tyr*to sulfonium inside the binding pocket enables selective crosslinking.In consequence,methyllysine readers with tyrosine-containing aromatic cages could be selectively crosslinked by site-specific sulfonium peptide probes.In addition,we expanded substrates from aromatic cages to tyrosine residues of proximate contact with sulfonium probes.The pair of LgBiT and SmBiT exhibited orthogonal crosslinking in complicated cell samples.As a result,we may expand sulfonium tools to target local tyrosine in future investigations.
文摘A novel strategy for site-selective benzylic C–H oxidation has been developed through mediated electrolysis.A bulky maleimide N-oxyl radical(MINO)generated by proton-coupled electrochemical oxidation of N-hydroxymaleimide(NHMI),serves as a hydrogen atom-transfer mediator.Good-to-excellent site selectivity was observed among different substrates,providing a practical approach for site-selective benzylic C–H oxidation.Additionally,the hydrogen-atom transfer mechanism for C–H electrochemical oxidation allows the oxidation to proceed at much lower anode potentials relative to direct electrolysis and with minimal reliance on the substrate's electronic properties.
文摘Late-stage modification of complex molecules via site-selective hydrodefluorination is a challenging endeavor.The selective activation of carbon-fluorine(C-F) bonds in the presence of multiple C-F bonds is of importance in organic synthesis and drug discovery.Herein,we describe the activation of C-F bonds via multiphoton photoredox catalysis to selectively produces a series of hydrodefluorinated compounds by simply tuning the reaction conditions.Moreover,this protocol was successfully applied to the late-stage functionalization of different drug-derivatives and the corresponding mono-,di-,and tri-defluorinated products were obtained in good to excellent yields.A detailed mechanistic investigation provides insight into the unprecedented hydrodefluorination pathway.
基金Jiangsu Province(No.BK20161307 and“333”Talents Project for H.Hu)Huaiyin Normal University(No.JSKC18014)for their financial support。
文摘A rhodium-catalyzed directing group promoted selective C-H olefination reaction of indolizines at the 8-position is re ported.Di-olefination at 2,8-positions also achieved with silver hexafluoroantimonate as an additive under similar reaction conditions.Weakly coordinating groups,such as ketone,alde hyde,amide and ester,were used as directing groups.The ester group can be removed under acid conditions and therefore is used as a traceless directing group.
基金Financially supported by the National Natural Science Foundation of China(No.21267014 and 21567017)
文摘The electronic structure of Eu-doped NaTaO3 in Na-rich environment is investigated by the first-principles theory. By simulating the two different models of Eu3＋ ions selectively located in Ta and Na sites, respectively, the band gaps of two Eu-doped NaTaO3 models were all narrowed, which were assigned to lattice defects and impurity band of the Eu dopent. For the model of Eu3＋ ions located in the Na＋ sites of NaTaO3, the new impurity band mainly composited of Eu 4f orbital appeared at the top over the valence band, indicating the enhanced oxidative ability. For the model of Eu3＋ ions located in the Ta5＋ sites of NaTaO3, a midgap state generated was located at the bottom of conduct band and the band potential shifted up, confirming the strong reductive ability in the Na-rich enviornment. The densities of electron states were significantly increased in both the conduction and valence bands in Na-rich model, which resulted in the increased carrier migration rate and thus photocatalytic activity enhancement. It is proposed that Eu3＋ ions doping at the Ta sites could enhance the reduced photocatalytic performance via controlling the nonstoichiometric Na/Ta molar ratio in the Eu-doped NaTaO3 system.
基金Financial support from the National Natural Science Foundation of China(No.22171145 to Z.Jin,32072440 to X.Xu)is gratefully acknowledged.
文摘Transition-metal-catalyzed remote sp^(2)C-H functionalization of aryl sulfonic acids was hardly ever real-ized owing to competitive ortho-C-H functionalization of aryl sulfonates and electron-deficient nature of phenyl ring.Herein,with the assistance of a practical biaryl indolyl directing template,palladium-catalyzed remote sp^(2)C-H alkylation of aryl sulfonic acids have been achieved in moderate to good yields with exclusive meta selectivity.Moreover,remote meta-selective C-H alkynylation of aryl sulfonic acids was also accomplished with a rhodium catalyst.These meta-C-H functionalized products proved to be the superior synthetic precursors,which are difficult to access using the conventional strategy.
基金supported by the National Natural Science Foundation of China (Grant Nos.22176181,11874329,11934020,and U1930121)the Foundation of the President of China Academy of Engineering Physics (Grant No.YZJJZQ2022011)the Foundation of Science and Technology on Surface Physics and Chemistry Laboratory (Grant No.WDZC202101)。
文摘We investigate the electronic structure ofβ-uranium,which has five nonequivalent atomic sites in its unit cell,by means of the density functional theory plus Hubbard-U correction with U from linear response calculation.It is found that the 5f electronic correlations inβ-uranium are moderate.More interestingly,their strengths are site selective,depending on the local atomic environment of the present uranium atom.As a consequence,the occupation matrices and partial 5f density of states ofβ-uranium manifest site dependence.In addition,the complicate experimental structure ofβ-uranium could be well reproduced within this theoretical framework.
基金the National Natural Science Foundation of China(No.50702029)Shandong Provincial Education Department(No.J05D08)Natural Science Foundation of Qingdao(No.05-1-JC-89)
文摘Ordered zinc oxide （ZnO） rod arrays with very high orientation were fabricated on Si substrates by using a solution method. The substrate surfaces were functionalized by Self-Assembly Monolayers （SAMs）. In the very early growth stage, the oriented ZnO crystals had already grown, which appeared to be the main reason why ZnO nanorods showed very high orientation. The un-dense and un-uniform SAMs provided a surface that was heterogeneous to ZnO nucleation. Consequently, highly oriented ZnO rods were selectively grown on the ＂coin-like＂ SAM-uncovered regions. The route developed here can provide some helpful information to control the nucleation and orientation of ZnO in aqueous solution. Also, the site-selective growth mechanisms can indicate a clue to grow patterned highly oriented ZnO nanorod arrays by the organic template.
文摘The rare earth berate YBO3 synthesized by sol-gel technique was found to be in two phases. However, the low-svmmetry form of YBO3 which was found also in some other rare earth (Sm, Eu, Gd) berates has a much different dependence on the preparing conditions, The photoluminescent spectra indicate that there are more than two sites for Eu3+ in the sol-gel prepared polycrystalline YBO3:Eu with low-symmetry.
基金The financial support from the National Recruitment Program of Global Youth Experts(1000 Talents Plan)the National Natural Science Foundation of China (No. 81703406)
文摘Recent years have seen an ever increasing number of enzyme mediated protein/peptide modification reactions, which contribute significantly to the elucidation of related biological functions. The many available enzymes have, however, caused difficulties for practitioners in choosing the most appropriate enzyme for a certain purpose. This review surveyed the widely used enzymes(i.e., sortases, butelase 1,subtiligase, formylglycine generating enzyme and farnesyltransferase) in the manipulation of proteins/peptides, and the application fields of these enzymes as well as the advantages and limitations of each enzyme are summarized.
基金supported by the US National Science Foundation(CHE-1808788).
文摘Controlled growth of islands on plasmonic metal nanoparticles represents a novel strategy in creating unique morphologies that are difficult to achieve by conventional colloidal synthesis processes,where the nanoparticle morphologies are typically determined by the preferential development of certain crystal facets.This work exploits an effective surface-engineering strategy for site-selective island growth of Au on anisotropic Au nanostructures.Selective ligand modification is first employed to direct the site-selective deposition of a thin transition layer of a secondary metal,e.g.,Pd,which has a considerable lattice mismatch with Au.The selective deposition of Pd on the original seeds produces a high contrast in the surface strain that guides the subsequent site-selective growth of Au islands.This strategy proves effective in not only inducing the island growth of Au on Au nanostructures but also manipulating the location of grown islands.By taking advantage of the iodide-assisted oxidative ripening process and the surface strain profile on Au nanostructures,we further demonstrate the precise control of the islands’number,coverage,and wetting degree,allowing fine-tuning of nanoparticles’optical properties.
基金supported by the National Science Foundation of China(no.22071267)the National Science and Technology Major Project“Key New Drug Creation and Manufacturing Program,”China(no.2020ZX09201015)+1 种基金the Innovation Team of the“DoubleFirst Class Initiative”(nos.CPU2018GY04 and CPU2018GY35)the Foundation of the Open Project of State Key Laboratory of Natural Medicines(no.SKLNMZZ202023).
文摘Many of the commonly used pharmaceuticals and biologically active natural products are nitrogencontaining compounds.Recently,the transitionmetal-catalyzed or the radical-mediated 1,2-carboamination of alkenes has been well explored to access amine scaffolds.However,synthetic strategies toward the 1,1-carboamination of alkenes are severely limited.Herein,we describe a method to achieve the 1,1-arylamination using readily available building blocks enabled by palladium catalysis.This sequential three step-Heck arylation,metal migration,followed by aza-1,6-Micheal addition process exhibits excellent chemo-and regioselectivity.To showcase the potential as a method for diversity-oriented drug discovery,the modification of numerous structurally complex bioactive molecules was also successfully performed.
基金the Central Universities(Nos.SWU-KF25028 and SWU-XDJH202314)Natural Science Foundation Project of Chongqing(No.cstc2024ycjh-bgzxm0005)the Opening Project of State Key Laboratory of Solid Lubrication(No.LSL2416)for financial support.We also thank Analytical&Testing Center in Southwest University for SEM test.
文摘Perovskite barium titanate(BaTiO3)demonstrates exceptional dielectric properties as a promising microwave-absorbing(MA)material.Leveraging structural flexibility of perovskites,magnetic components can be incorporated at A/B-sites to enhance MA performance,yet the fundamental disparity in MA mechanisms between A/B-site magnetic doping remains elusive.Herein,nickel-doped BaTiO3 perovskites were systematically synthesized through precise adjustment of the Ba/Ti molar ratio to achieve both A-site(Ni_(x)Ba_(1−x)TiO_(3),N_(x)BTO)and B-site(BaTi_(1−x)Ni_(x)O_(3),BTN^(x)O)substitutions(0≤x≤0.1)via a simple one-step hydrothermal method.Notably,A-site Ni^(2+)substitution in N_(x)BTO induced superior magnetic loss(tanδμ=0.39)attributed to eddy-current dissipation,while B-site doping in BTN^(x)O achieved higher dielectric loss(tanδε=0.49).The N0.1BTO sample exhibited optimal MA performance with a remarkable minimum reflection loss(RLmin)of−44.39 dB and broad effective absorption bandwidth(EAB=8.66 GHz)covering the Ku-band and 67%X-band.Multimodal analysis revealed synergistic interactions among multiple reflection and scattering,multi-polarization relaxation,natural resonance,and eddy currents.In contrast,BTN0.01O demonstrated deeper RLmin(−50.88 dB)but narrower EAB(3.33 GHz)governed by dielectric mechanisms.Structural characterization indicated A-site doping induced lattice distortion,reduced unit-cell volume,and optimized oxygen vacancy distribution,synergistically balancing magneto-dielectric parameters.Conversely,B-site substitution increased oxygen vacancy concentration and carrier mobility while amplifying dielectric fluctuations.The spatial occupation preference of A/B dopants(A-site and B-site)governs lattice symmetry breaking,consequently establishing structure-property relationships and underpinning the material’s tunable dielectric behavior and magnetic phenomena.This work proposes a site-selective doping strategy for designing high-performance perovskite MA materials through magneto-dielectric equilibrium optimization.
基金funding from the National Natural Science Foundation of China(grant nos.22071209,22071206)the National Youth Talent Support Program,the Natural Science Foundation of Fujian Province of China(grant no.2017J06006)the Fundamental Research Funds for the Central Universities(grant no.20720190048).
文摘The direct conversion of unactivated alkanes and cycloalkanes into structurally diverse molecules through aliphatic C—H functionalization is a useful process, which has attracted intense interest from academia and industry. Methods to control chemo- and site-selectivity, combined with asymmetric catalysis, provide appealing access to high value-added enantiomer-enriched compounds but are far less developed. This review focuses on recent progress in (i) asymmetric reactions of alkanes or cycloalkanes with prochiral substrates which generate a stereocenter adjacent to the cleaved C(sp3)–H bond, and (ii) C(sp3)–H enantiodiscriminatory reactions creating a new stereogenic center on the carbon of a cleaved C(sp3)–H bond. Elegant strategies are discussed, including (a) metal carbene-induced C—H insertions by chiral rhodium catalysts, (b) metal-oxo-mediated C—H oxidation by biomimetic manganese catalysts, (c) enzyme catalysis by cytochromes P450 variants, and (d) dual catalysis by a photocatalyst and a chiral Lewis acid (CLA) or a chiral phosphoric acid (CPA). These catalytic systems can not only precisely recognize primary, secondary and tertiary C—H bonds at specific positions in alkanes and cycloalkanes, but also support a high level of stereoselectivity in the reactions. It is expected that the advances will stimulate further progress in asymmetric catalysis, synthetic methodology, pharmaceutical development and industrial processes.
基金support by Hainan Provincial Natural Science Foun-dation of China(220QN180,2019RC028,2019RC129,221QN173,221QN172)Hainan University Start-up Funds(KYQD(ZR)1854 and KYQD(ZR)1857)was appreciated.
文摘A novel benzyl cation-triggered site-selective sp^(2) C—H phosphorylation and etherification was developed. This reaction was conducted under the transition metal-free conditions through cation migration via dearomatization. Under the reaction conditions, the derivatives of naphthalenes, benzofurans and benzo[b]thiophenes all can be transformed into the corresponding products in good to excellent yields. It provides a method to construct sp^(2) C—P and sp^(2) C—O bonds as well as a new strategy for benzylic activation-triggered sp^(2) C—H functionalization.
基金supported by the National Natural Science Foundation of China (22174104 to Q.Z.)the support of the Hubei Provincial Natural Science Foundation of China (2022CFB627)the Fundamental Research Funds for the Central Universities (20422022kf1039)。
文摘Rational design and construction of chiral-achiral hybrid structures are of great importance to realize the multifunctional complex chiral structures toward emerging technological applications. However, significant challenges remain due to the lack of fine control over the heterostructure. Here, we have developed a general bottom-up synthetic strategy for the site-selective growth of Cu nanodomains on intrinsically chiral Au nanocrystals. Chiral AuCu heterostructures with three distinct architectures were achieved by controlling the overgrowth of Cu nanodomains in a site-specific manner. The geometry-dependent plasmonic chirality of the heterostructures was demonstrated experimentally by circular dichroism spectroscopy and theoretically through finite-difference time-domain simulations. The site-specific geometric control of chiral AuCu heterostructures was also extended to employ anisotropic chiral Au nanoplates and nanorods as the building blocks. By virtue of the galvanic replacement reactions between metal ions and Cu atoms, chiral heterostructures with increasing architectural complexity and compositional diversity can be further achieved. The current work not only opens up a promising strategy to synthesize complex chiral hybrid nanostructures but also provides an important knowledge framework that guides the rational design of multifunctional chiral hybrid nanostructures toward chiroptical applications.
基金We are grateful for financial support from the Natural Science Foundation of Yunnan Province,China(No.2019FY003003)the Scientific and Technological Innovation Team of Green Synthesis and Activity Research of Natural-like Heterocyclic Compound Libraries in Universities of Yunnan Province(No.C17624011121).The authors thank the Advanced Analysis and Measurement Center of Yunnan University for the sample testing service.
文摘A novel protocol for the preparation of highly functionalized 2-azabicyclo[3.3.1]nonane(morphan)derivatives via a multicomponent cascade reaction,involving 3-formylchromones,2-naphthols,and enaminones in the ionic liquid[BMIM]PF6 as the solvent and promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU),was developed,which involved the cleavage of one C–O bond and formation of four bonds(1 C–O,1 C–N,and 2 C–C bonds).As a result,a series of morphan derivatives were produced through a cascade reaction,including a sequence of 1,2-addition,enol-keto tautomerization,Michael addition,dehydration,another Michael addition,imine-enamine tautomerization,and N-alkylation reactions,which were accompanied by a ring-opening reaction.This protocol was suitable for combinatorial and parallel syntheses of natural product-like morphan compounds in a one-pot reaction rather than through tedious multi-step reactions.
基金financially supported by grants from the National Natural Science Foundation of China(nos.21907004 and 81821004)the National Key R&D Program of China(no.2018YFA0507602)the Beijing Outstanding Young Scientist Program(no.BJJWZYJH01201910001001).
文摘The development of a facile cysteine-directed S-glycosylation strategy would facilitate the intensive investigation of the effect of glycosylation on protein translational modification.Herein,we introduce glycosyl Bunte salt as an efficient glycosyl donor for site-selective peptide/protein modification.The coupling reaction with cysteine thiols under alkaline buffer conditions proceeded chemoselectively,delivering homogeneous glycoconjugates and inorganic salt as the only byproduct.A series of sugar moieties,including monosaccharides and oligosaccharides,were successfully conjugated to the peptides and protein via the disulfide bond.Furthermore,this protocol was applied to the glycosylation of the glucagon-like peptide 1(GLP-1)variant,and its glycosylated effect on blood glucose control was also studied.
