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991.
The organocatalysed asymmetric hydrosilylation of a number of N-aryl and alkyl β-substituted enamino esters proceeds in generally good yield and enantioselectivity. Crucial to obtaining high yield and selectivity was the addition of benzoic acid as an additive and under these conditions, both N-alkyl and N-aryl substituents were well tolerated. β-Aryl and alkyl substituents were evaluated and a model proposed to account for the experimental observations based upon enamine tautomerisation and conformational preferences of the reactive ketimine intermediate. 相似文献
992.
A model study of DNA-directed peptide ligation has been developed by transferring fluorescent reporting group from small molecule thioester to a DNA strand (template DNA) in the presence of a thiol-functionalized DNA strand (auxiliary DNA), mimicking the Native Chemical Ligation (NCL) reaction. This DNA-directed transfer shows dependence on the sequence complementarity of the two DNA strands, with in situ generated 4-thiolphenylmethyl functionalized oligonucleotide as the auxiliary DNA strand, under mild basic condition (pH=8.5), and with tris(2-carboxyethyl) phosphine hydrochloride (TCEP) as a reducing agent. Reactions with different amino acid α-thioesters resulted in varied transfer efficiencies from glycine to α-substituted amino acids. This study has provided the basic foundation to use DNA-programmed chemistry toward the chemical synthesis or unnatural modification of protein molecules. 相似文献
993.
Reported herein is the FeCl3-promoted intermolecular sulfoesterification of o-(1-alkynyl)benzoates with disulfides, which provides a convenient and efficient method for synthesis of 4-sulfenylisocoumarins. Various functional groups such as methoxy, halides, ester, cyano and silicon groups in the substrates are tolerated, and heterocycle-fused chalcogenylpyrones are also successfully achieved directly from the corresponding heterocyclic precursors under the same reaction conditions. In addition, starting from diynylbenzoate, this reaction sequence can be combined with a bicyclization step leading to the tetracyclic (E)-3-(2-phenyl-3-phenylchalcogenylinden-1-ylidene)isobenzofuranone frameworks with high regiospecificity and exclusive trans stereoselectivity. 相似文献
994.
A palladium-based catalyst (Fe3O4/SiO2/HPG–OPPh2–PNP) supported on chlorodiphenylphosphine-functionalized magnetic nanoparticles was successfully prepared from Fe3O4/SiO2 with sequential attachment of glycerol and chlorodiphenylphosphine, followed by treatment of an ethanolic solution of palladium chloride with hydrazine. The as-prepared catalyst was characterized by ICP-AES, FTIR, XRD, SEM, and TEM. The Fe3O4/SiO2/HPG–OPPh2–PNP was found as a magnetically separable and highly active catalyst for Suzuki coupling reactions of aryl iodides, bromides, and chlorides as well as Heck reactions of aryl iodides and bromides. Under appropriate conditions, all reactions afforded the desired products in moderate to excellent yields. Moreover, this catalyst can be easily recovered by using a magnetic field and directly reused for at least six cycles without significant loss of its activity. 相似文献
995.
δ-Glyconolactams were first synthesized by the intramolecular Schmidt–Boyer reaction using corresponding δ-azidosugars as starting material. The reaction could be efficiently performed in good yields of 61–69% under microwave radiation in acid condition, providing an alternative protocol to iminosugar δ-lactam. 相似文献
996.
The reaction of [60]fullerene with diethyl aminomalonate hydrochloride and carbon disulfide in the presence of triethylamine gave a [60]fullerene-fused thiolactam, which could be hydrolyzed, S-alkylated, and N-acylated in high yields. 相似文献
997.
Isomers based on the bisindolylmaleimide architecture were reported in this Letter. Introducing hydroxyl to this architecture lead to quenching the fluorescence of bisindolylmaleimide. The fluorescence was recovered with its hydroxyl group esterified. Ester group can be easily transformed to hydroxyl group by hydrolysis reaction. Thus, a toggle-switchable fluorescence, ‘off-on’ cycle can be established on the basis of reversible esterification/hydrolysis reaction. 相似文献
998.
Fanbo SongJing Zhang Quanbin CuiTing Wang Wenbin ChenLuyuan Li Zhen Xi 《Tetrahedron letters》2012,53(9):1102-1104
Inositol phosphates regulate important biological functions in intracellular signal transduction events. Phosphonates, because of the stability towards the action of phosphatases, were extensively used to replace phosphates. We herein reported the synthesis of inositol phosphonate analogues using myo-inositol as the starting material, and found that two of phosphonate analogues exhibited relative good cytotoxic activity against non-small cell lung cancer (NSCLC) cell line A549. 相似文献
999.
Abstract. A novel germanate compound, |[Ni(dien)2]3(H2O)3|[Ge7O13F5]2(designated JU‐85, dien = diethylenetriamine), was solvothermally synthesized. The structure of JU‐85 was determined by single‐crystal X‐ray diffraction and further characterized by powder X‐ray diffraction, inductively coupled plasma, infrared spectroscopy, elemental analysis, and thermogravimetric analysis. JU‐85 has dissymmetric chains constructed from diagonally linked Ge7 building units and various Ni(dien)22+ complexes formed in situ during the synthesis. Compared with its structural analogue, FJ‐6, JU‐85 contains less complex cations and different host‐guest assembly. Besides the diagonal linkage in JU‐85, other dissymmetric linkages of Ge7 building units were enumerated, which could be used as the stereogenic centers for the design of novel chiral germanate compounds. 相似文献
1000.