Topic
Substituent
About: Substituent is a research topic. Over the lifetime, 42877 publications have been published within this topic receiving 516716 citations. The topic is also known as: side chain & side group.
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16 Jul 1997TL;DR: In this paper, an olefin polymerization process comprising contacting ethylene alone or with one or more OOlefinically unsaturated comonomers with a Group 3-6 metallocene catalyst compound comprising one π-bonded ring having a C 3 or greater hydrocarbyl substituent is described.
Abstract: The invention comprises an olefin polymerization process comprising contacting ethylene alone or with one or more olefinically unsaturated comonomers with a Group 3-6 metallocene catalyst compound comprising one π-bonded ring having a C 3 or greater hydrocarbyl, hydrocarbylsilyl or hydrocarbylgermyl substituent said substituent bonded to the ring through a primary carbon atom; and, where the compound contains two π-bonded rings, the total number of substituents on the rings is equal to a number from 3 to 10, said rings being asymmetrically substituted where the number of substituents is 3 or 4. The invention process is particularly suitable for preparing ethylene copolymers having an MIR less than about 35, while retaining narrow CD even at high comonomer incorporation rates, and with certain embodiments providing ethylene copolymers having improved melt strength with the low MIR.
75 citations
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TL;DR: The proposed palladium oxidative addition complexes demonstrate the potential for palladium-mediated methods to serve as a platform for the development of future cross-linking techniques for peptides and proteins with natural amino acid residues.
Abstract: A new method for cysteine–lysine cross-linking in peptides and proteins using palladium oxidative addition complexes is presented. First, a biarylphosphine-supported palladium reagent is used to transfer an aryl group bearing an O-phenyl carbamate substituent to a cysteine residue. Next, this carbamate undergoes chemoselective acyl substitution by a proximal lysine to form a cross-link. The linkage so formed is stable toward acid, base, oxygen, and external thiol nucleophiles. This method was applied to cross-link cysteine with nearby lysines in sortase A*. Furthermore, we used this method for the intermolecular cross-linking between a peptide and a protein based on the p53-MDM2 interaction. These studies demonstrate the potential for palladium-mediated methods to serve as a platform for the development of future cross-linking techniques for peptides and proteins with natural amino acid residues.
75 citations
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TL;DR: A new method for the 18F-radiolabeling of aromatic compounds based on the aromatic nucleophilic substitution (SNAr) reaction using triarylsulfonium salts has been developed and indicates that sulfonium ions have the potential to be optimized for labeling nonactivated and deactivated aryl rings that have Hammett σP substituent constants greater than –0.170.
75 citations
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TL;DR: A novel series of melatonin receptor ligands, characterized by a N-(substituted-anilinoethyl)amido scaffold, along with preliminary structure-activity relationships (SARs), is presented, showing promising sleep-promoting and antianxiety properties in animal models.
Abstract: A novel series of melatonin receptor ligands, characterized by a N-(substituted-anilinoethyl)amido scaffold, along with preliminary structure–activity relationships (SARs), is presented. MT1 and MT2 receptor binding affinity and intrinsic activity have been modulated by the introduction of different substituents on the aniline nitrogen, on the benzene ring, and on the amide side chain. Modulation of intrinsic activity and MT2 selectivity of the newly synthesized compounds has been achieved by applying SAR models previously developed, providing compounds with different binding and intrinsic activity profiles. Compound 3d, with a bulky s-naphthyl group, behaves as an MT2-selective antagonist with sub-nM affinity. Size reduction of the substituent enhances intrinsic activity, as in the nonselective N-methyl-anilino agonist 3i. The phenyl derivative 3g is an MT2-selective partial agonist, with MT2 binding affinity higher than melatonin, showing promising sleep-promoting and antianxiety properties in animal mo...
75 citations
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TL;DR: In this paper, the authors observed that the efficiency of ECL quenching is directly related to the position of the substituted phenols on the aromatic ring, with meta derivatives displaying the greatest magnitude of quench.
Abstract: Efficient quenching of Ru(bpy)32+ (bpy =
2,2′-bipyridine) electrogenerated chemiluminescence (ECL) was
observed in the presence of phenol and substituted phenols (e.g.,
4-fluorophenol). Spectroscopic and electrochemical studies indicated that
the mechanism of quenching involves energy transfer from the excited state
luminophore to a benzoquinone derivative formed at the electrode. The
efficiency of ECL quenching is directly related to the position of the
substituent on the aromatic ring, with meta derivatives displaying
the greatest magnitude of quenching. The degree of quenching does not
appear to be related to the electron-donating or -withdrawing ability of
the phenol substituent.
75 citations