查看更多>>摘要：The scope of stereochemistry recognition usually occurs near the chiral scaffold of a ligand or catalyst.Remote stereocontrol,which can surpass the limits of stereorecognition of remote prochiral centers,has long been a challenging object of great interest in asymmetric catalysis.The current work realized the remote stereocontrol of 1,7-zwitterion intermediates formed from Huang's o-amino aryl MBH carbonates.With simple and easily accessible β-ICD as the bifunctional catalyst,multifunctionalized tetrahydroquino-line derivatives could be synthesized via(4+2)cycloadditions with excellent enantioselectivity and di-astereoselectivity under mild conditions.The strategy possesses broad substrate scope,and three types of electron-deficient enones are successfully applied.Mechanistic studies disclosed the Lewis base-catalyzed reaction pathway,and H-bonding between the catalyst and enones is crucial for long-range stereocontrol.Scale-up reaction and transformations of the tetrahydroquinoline products demonstrated the potential of this strategy.
查看更多>>摘要：A method for the generation of alkyl radicals from inert alkyl C-O bonds has been developed via an iron/borane reagent/alkoxide catalytic system,which can be employed for the synthesis of amines from nitroarenes with excellent efficiency.This reductive amination features good functional group compatibil-ity and enables the late-stage amination of bio-relevant compounds,thus providing good opportunities for applications in medicinal chemistry.Preliminary mechanistic studies reveal that the amine synthesis may be involving a Fe/Li cation-assisted single electron transfer pathway to form alkyl radicals,and the low-valent iron species may be the active intermediates.
查看更多>>摘要：A H4SiW12O40-catalyzed three-component tandem reaction of 2-acylbenzoic acids,primary amines and phosphine oxides to form 3,3-disubstituted isoindolinones was developed.By employing H4SiW12O40 as the catalyst and dimethyl carbonate(DMC)as the solvent,a diverse range of 2-acylbenzoic acid deriva-tives and primary amines worked well to give the C3-phosphinoyl-functionalized 3,3-disubstituted isoin-dolinones with the yield range of 61％-87％.Advantages of this transformation include green catalyst and solvent,available starting materials,broad substrate scope,high efficiency and operational simplicity with water as the sole by-product.The strategy achieved an efficient and green molecular fragment assembly to access isoindolinones,which would provide opportunities for the synthesis of potential biologically active molecules in a green manner.
查看更多>>摘要：Unnatural amino acids(UAAs)have broad applications in pharmaceutical sciences and biological studies.Current synthetic methods for UAAs mainly rely on asymmetric catalysis and often require several steps.There is a lack of direct and simple methods.To address this challenge,we designed the LADA(labeling-activation-desulfurization-addition)strategy:selective labeling and activation of cysteine residues,the photocatalytic desulfurization and the subsequent radical addition to alkenes.Although composed of two steps,it is one-pot synthesis and has advantages such as high functional group tolerance,biocompatible reaction condition,and retained stereochemistry.This highly efficient strategy was successfully applied in the direct synthesis of unnatural amino acids and modifications of peptides with more than 50 examples.
查看更多>>摘要：Photocatalytic and photoinduced silyl radicals cascade cyclization procedures for the green and sim-ple preparation of fused tetracyclic skeleton silylated indolo[2,1-a]isoquinoline-6(5H)-ones from 2-aryl-N-acryloyl indoles with hydrosilanes are developed.The photocatalytic reaction is carried out with 9,10-dicyanoanthracene(DCA)as an organophotocatalyst and 3-acetoxyquinuclidine as hydrogen atom transfer(HAT)catalyst at room temperature under metal-and oxidant-free conditions.The keys to the success of photoredox-catalytic conversion include(1)the reductive quenching of DCA*[E1/2(*P/P-)=+1.97 V vs.SCE in MeCN]by 3-acetoxyquinuclidine(Ep=+1.22 V vs.SCE in MeCN),and(2)the thermodynamic feasibil-ity of hydrogen atom abstraction from hydridic Si-H bond by electrophilic N+·.Particularly,the simple photoinduced cascade cyclization using(TMS)3SiH with 2-aryl-N-acryloyl indoles was exploited via an electron-donor-acceptor(EDA)complex under visible light irradiation.
查看更多>>摘要：A general,facile and eco-friendly iron catalysis enables oxidation of unstrained tertiary aromatic alcohols to ketones through C-C bond cleavage even with H2O2 as the oxidant.Notably,this transformation can tolerate oxidation-labile functional groups.The robustness of this method is further demonstrated on the late-stage oxidation of complex bioactive molecules.
查看更多>>摘要：Nucleophilic phosphine and amine catalyst-switched chemodivergent[4+1]and[3+3]annulations of allenyl imides and β,γ-enones have been developed,furnishing highly substituted 2-cyclopentenone and 2-pyranone derivatives in moderate to excellent yields.Two plausible reaction mechanisms involving two different ketene intermediates have been proposed to explain the observed chemoselectivity.Moreover,by virtue of the α,β-enone substructure of the[4+1]adducts,1,3-dipolar cycloaddition of nitrile imines has been studied in one-pot to provide various fused pyrazoline derivatives.
查看更多>>摘要：Implantable system maximizes drug concentration and continuously releases drugs near the tumor,which is an effective tool to solve the difficult retention of chemotherapy drugs in bladder cancer.In this work,a novel polysaccharide supramolecular injectable hydrogel(CCA hydrogels for short)is rapidly con-structed by simply mixing cationic chitosan,anionic sulfobutyl ether β-cyclodextrin(SBE-β-CD)and a trace amount of silver ions.The injected hydrogel reconstituted and regained its shape in less than 1 h,and it can still maintain the elasticity suitable for the human body.By packaging the drug directly,the gel achieves a high concentration of doxorubicin,an anticancer drug.Using MB49-luc cells as the model of bladder tumor for anti-tumor in vivo,the CCA-DOX gel has obvious inhibitory effect on bladder tu-mor,and its inhibitory effect is much greater than that of free DOX.Therefore,this self-healing injectable hydrogel has great potential for in situ treatment of bladder cancer.
查看更多>>摘要：A new strategy to induce vesicle fusion has been developed by employing pillar[5]arene derivatives that were channel-like and were prepared by appending side chains onto pillar[5]arenes backbones.The chan-nels feature with hydrophilic negatively and positively charged groups at both ends and hydrophobic Trp residues at the outer surface,which endows the channels with amphiphilicity.The zwitterionic am-phiphilic channels could spontaneously incorporate into the bilayer membranes of lipid vesicles to induce vesicle fusion driven by the electrostatic interactions between negatively charged and positively charged groups.
查看更多>>摘要：The development of molecular probes or systems with the ability of multiple orthogonal responses is an effective approach to precisely detect biomolecules with similar chemical structures.Herein,we report the synthesis of a water-soluble TPE-based octacationic cage(1)with the compressed TPE-containing bilayer,which endows it with good fluorescence properties and potential conformation chirality.As a re-sult,1 exhibits molecular recognition for anionic nucleotides within its two"claw"-like cavities to form 1:2 host-guest complexes in water,companying with selective turn-off fluorescence and turn-on CD re-sponses to G/GTP over other nucleotides.
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