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.

4-Bromo or 4-iodo phenylamino benzhydroxamic acid derivatives and their use as MEK inhibitors

Abstract: Phenylamino benzhydroxamic acid derivatives of formula (I) where R1, R2, R3, R4, R5, and R6 are hydrogen or substituent groups such as alkyl, and where R7 is hydrogen or an organic radical, are potent inhibitors of MEK and, as such, are effective in treating cancer and other proliferative diseases such as psoriasis and restenosis.

A Simple Iridium Catalyst with a Single Resolved Stereocenter for Enantioselective Allylic Amination. Catalyst Selection from Mechanistic Analysis

Abstract: A study of the relationship between the stereochemical elements of a phosphoramidite ligand and the stereoselectivity of iridium-catalyzed amination of allylic carbonates is reported. During catalyst activation, a complex of a phosphoramidite ligand possessing one axial chiral binaphtholate group and two resolved phenethyl substituents converts to a more reactive cyclometalated complex containing one distal chiral substituent at nitrogen, one substituent that becomes part of the metalacycle, and one unperturbed binaphtholate group. Systematic changes were made to the different stereochemical elements. Replacement of the distal chiral phenethyl substituent with a large achiral cycloalkyl group led to a catalyst that reacts with rates and enantioselectivities that are similar to those of the original catalyst with the phenethyl group. Studies of the reactions of diastereomeric ligands containing (R) or (S) binaphtholate groups on phosphorus, along with one (R)-phenethyl and one achiral cyclododecyl group on...

Antibacterial and Hemolytic Activities of Quaternary Pyridinium Functionalized Polynorbornenes

Abstract: In this study, amphiphilic polyoxanorbornene with different quaternary alkyl pyridinium side chains were synthesized. The biological efficiencies of these polymers, with various alkyl substituents, were determined by bacterial growth inhibition assays and hemolytic activity (HC 50 ) against human red blood cells (RBCs) to provide selectivity of these polymers for bacterial over mammalian cells. A series of polymers with different alkyl substituents (ethyl, butyl, hexyl, octyl, decyl and phenylethyl) and two different molecular weights (3 and 10 kDa) were prepared. The impact of alkyl chain length divided the biological activity into two different cases: those with an alkyl substituent containing four or fewer carbons had a minimum inhibitory concentration (MIC) of 200 μg. mL -1 and a HC 50 greater than 1650 μg. mL -1 , while those with six or more carbons had lower MICs < 12.5 μg. mL -1 and HC 50 ≤ 250 μg. mL -1 . Using MSI-78, the potent Magainin derivative which has an MIC=12.0 μg·mL -1 and HC 50 = 120 μg·mL -1 , as a comparison, the polymers with alkyl substituents ≤C 4 (four carbons) were not very potent, but did show selectivity values greater than or equal to MSI-78. In contrast, those with alkyl substituents ≥C 6 were as potent, or more potent, than MSI-78 and in three specific cases demonstrated selectivity values similar to, or better than, MSI-78. To understand if these polymers were membrane active, polymer induced lipid membrane disruption activities were evaluated by dye leakage experiments. Lipid composition and polymer hydrophobicity were found to be important factors for dye release.

Determination of the Substituent Effect on the O−H Bond Dissociation Enthalpies of Phenolic Antioxidants by the EPR Radical Equilibration Technique

Abstract: The bond dissociation enthalpies (BDE) of several phenols containing electron-withdrawing substituents in the para position have been determined by means of the EPR radical equilibration technique. It has been found that CN, NO2, CHO, COOR, and COOH induce an increase of the BDE value of the O−H bond, thus producing a worsening of the antioxidant activity of phenols, while Cl, Ph, and CHCHPh show an opposite effect. The contributions of these substituents for the calculation of the BDE values in polysubstituted phenols by using the group additivity rule have also been derived. It is shown that this rule provides quite reliable predictions of bond strengths, so that the method can be conveniently used to estimate new data on substituted phenols.

Substituent Effects on Redox Potentials and Optical Gap Energies of Molecule-like Au38(SPhX)24 Nanoparticles

Abstract: A molecule-like substituent effect on redox formal potentials in the nanoparticle series Au38(SPhX)24 has been discovered. Electron-withdrawing “X” substituents energetically favor reduction and disfavor oxidation, and give formal potentials that correlate with Hammett substituent constants. The ligand monolayer of the nanoparticles is shown, thereby, to play a strong role in determining electronic energies of the nanoparticle core and is more than simply a protecting or capping layer. The substituent effect does not, however, detectably change the HOMO−LUMO gap energy, being identical for the HOMO and LUMO levels and presumably inductive in nature.