Search results for "Substituent"
showing 10 items of 353 documents
Effect of Substituents at Imide Positions on the Laser Performance of 1,7-Bay-Substituted Perylenediimide Dyes
2021
Perylenediimide (PDI) compounds with no substituents in their core are widely used as the active units of thin-film organic lasers. Recently, bay-substituted PDIs (b-PDIs) bearing two sterically hindering diphenylphenoxy groups at the 1,7-bay positions have received great attention because they show red-shifted emission with respect to bay-unsubstituted PDIs, while maintaining high photoluminescence (PL) quantum yields and low amplified spontaneous emission (ASE) thresholds even at high doping rates. However, their ASE photostability is relatively low compared to that of state-of-the-art PDIs. Thus, the design of b-PDIs with improved ASE photostability remains a challenge. Here, the synthes…
Glycosylated macromolecular conjugates of antiviral drugs with a polyaspartamide.
2004
Two new polymeric conjugates for specific liver targeting were prepared by conjugation of sugar moieties and antiviral drugs to alpha, beta-poly[N-2-(hydroxyethyl)-DL-aspartamide] (PHEA). PHEA-galactopyranosylphenylthiocarbamide-mono-O-succinylganciclovir (conjugate 7) and PHEA-mannopyranosylphenylthiocarbamide-O-succinylacyclovir (conjugate 8) were synthesized according to a multi-step procedure which allowed for obtaining high product yield and process standardization. Conjugate 7 contained 7.5 and 8.5% of galactose and ganciclovir (substituent/repeating unit, mol/mol), respectively, and conjugate 8 contained 14.2 and 10.8% of mannose and acyclovir, respectively. In vitro studies demonstr…
Pairwise effects of chlorine substituents on the13C NMR chemical shifts of dichlorobicyclo[2.2.1]heptanes (norbornanes)
1984
The 13C NMR spectra of nine dichlorinated bicyclo[2.2.1]heptanes (norbornanes) have been measured and assigned. The pairwise effects of chlorine substituents which cause deviations from the additivity of single-substituent effects were investigated and are discussed. The largest effect found is the high-field shift of carbons bearing vicinal cis substituents. In the case of geminal substitution deviations from additivity were found to be to low field and large in the γ, smaller in the β and negligible in the α chemical shifts. The observed deviations for 1,3-disubstituted cases vary from −3.2 to +1.1 ppm at different carbons, allowing no simple explanation. Replacement of α-hydrogen in a di…
Evaluation of Physicochemical Properties of Amphiphilic 1,4-Dihydropyridines and Preparation of Magnetoliposomes
2021
This study was focused on the estimation of the targeted modification of 1,4-DHP core with (1) different alkyl chain lengths at 3,5-ester moieties of 1,4-DHP (C12, C14 and C16)
Evaluation of Antiradical Activity and Reducing Capacity of Synthesised Bispyridinium Dibromides Obtained by Quaternisation of 4-Pyridyl-1,4-dihydrop…
2015
New bispyridinium dibromides based on the 1,4-dihydropyridine (1,4-DHP) cycle were synthesised in the reaction between 4-pyridyl-1,4-DHP derivatives and propargyl bromide. It has been shown that variation of the substituent position on the pyridine as well as small changes in the electronic nature of the 1,4-DHP cycle as a result of the substituent nature at the 3 and 5 positions do not affect the course of the reaction and in all cases the corresponding bispyridinium dibromides 4a–e were formed. The antiradical activity, using 1,1-diphenyl-2-picrylhydrazine as a free radical scavenger, and the reducing capacity using phosphomolybdenum complexes have been evaluated for the newly synthesise…
H2-Antihistaminika, 28. Mitt. Synthese und H2-antagonistische Wirkung 3-(3-piperidinomethyl-phenoxy)propyl-substituierter Kohlensäurederivate und Ana…
1986
Es wurden 3-(3-piperidinomethyl-phenoxy)propyl-substituierte Kohlensaurederivate wie Harnstoffe, Thioharnstoffe, Guanidine und Cyanoguanidine sowie analoge Nitroethendiamine dargestellt und am isolierten Meerschweinchenvorhof und zum Teil an der histaminstimulierten Sauresekretion der narkotisierten Ratte auf H2-antagonistische Wirkung untersucht. H2-Antihistaminics, XXVIII: Syntheses and H2-Antagonistic Activity of Derivatives of Carbonic Acid and Analogues Carrying a 3-[3-(Piperidinomethyl)phenoxy]propyl Substituent Derivatives of carbonic acid such as ureas, thioureas, guanidines, and cyanoguanidines as well as the analogous nitroethenediamines were prepared with a 3-[3-(piperidinomethyl…
Influence of Substituents in the Aromatic Ring on the Strength of Halogen Bonding in Iodobenzene Derivatives
2020
Halogen bonding properties of 3,4,5-triiodobenzoic acid (1, 2), 1,2,3-triiodobenzene (3), pentaiodobenzoic acid ethanol solvate (4), hexaiodobenzene (5a, 5b, 5c), 2,4-diiodoaniline (6), 4-iodoaniline (7), 2-iodoaniline (8), 2-iodophenol (9), 4-iodophenol (10), 3-iodophenol (11) and 2,4,6-triiodophenol (12) has been studied. The results suggested that substituents other than halogen in aromatic ring affect XB properties of iodine substituents in ortho-, meta- and para-positions. The effect depends on the electron-withdrawing/electron-donating properties of the substituent. Thus, electron-withdrawing substituents with negative mesomeric effect favor m-iodines to act as XB donors and o- and p-…
The Effect of Halogen Bonding on the Packing of Bromine Substituted Pyridine and Benzyl Functionalized Resorcinarene Tetrapodands in the Solid State
2012
The synthesis and characterization of new bromine-substituted pyridine and benzyl functionalized tetramethoxy resorcinarene tetrapodands are described and their solid-state structural properties and interactions were studied by single crystal X-ray crystallography. Three different crystal structures were obtained for the pyridine derivative and one for the benzyl derivative, which revealed that the interactions of the bromine substituent have an explicit effect on the crystal packing of the resorcinarene molecules. One of the structures obtained had very interesting halogen–halogen interactions with the same geometry as is generally found for compounds used in nonlinear optical studies.
Fluorine Scan of Inhibitors of the Cysteine Protease Human Cathepsin L: Dipolar and Quadrupolar Effects in the π-Stacking of Fluorinated Phenyl Rings…
2016
The π-stacking of fluorinated benzene rings on protein backbone amide groups was investigated, using a dual approach comprising enzyme-ligand binding studies complemented by high-level quantum chemical calculations. In the experimental study, the phenyl substituent of triazine nitrile inhibitors of human cathepsin L (hCatL), which stacks onto the peptide amide bond Gly67-Gly68 at the entrance of the S3 pocket, was systematically fluorinated, and differences in inhibitory potency were measured in a fluorimetric assay. Binding affinity is influenced by lipophilicity (clog P), the dipole and quadrupole moments of the fluorinated rings, but also by additional interactions of the introduced fluo…
The electronic substituent influence on the thermally allowed electrocyclic interconversion cyclobutene/butadiene. A MNDO study
1984
The effects of donor/acceptor substitution on the conrotatory cyclobutene/butadiene interconversion have not yet been experimentally studied. MNDO Synchronous Transit/MINIMAX calculations for all possible combinations of NH2/NH3 + 3 groups at the fissile single bond reveal very large substituent effects on the opening reactions and reverse cyclisations. Diamino(1b/2b), diammonio-(1c/2c) and amino-ammonio-substitutions (1d/2d) change the activation energy of the reference ring opening reaction (1a →2a) from 49.9 kcal/mol to 34.7, 29.8 and 26.0 kcal/mol, respectively. This rate enhancement parallels the monotone shift of the transition state pathcoordinate towards the cyclobutenes. Relative t…