Determination of positional weighting factors for the Swain and Lupton substituent constants f and r

Williams, Steven G.; Norrington, F. E.

doi:10.1021/ja00418a030

Cited by 46 publications

(25 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An empirical equation with the two substituent parameters, F and R [Eqn (1)] was obtained for each of the ureido hydrogens, NH 1 and NH 3 , optimizing the f and r weighting factors by a bilinear regression analysis (all multiple linear regressions were performed with the SPSS 10.0.6 para Windows software package). 20 The Swain-Lupton F and R values used were scaled for the fluorinated aromatic positions (ortho, meta and para) according to the Williams-Norrington model, 21 and were calculated for each urea using additivity principles ( F and R).…”

Section: Resultsmentioning

confidence: 99%

¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

et al. 2005

View full text Add to dashboard Cite

Seventeen N-(mono-, di-, tri-, tetra- and penta-fluorophenyl)-N'-(3-nitrophenyl)ureas were prepared and characterized. Complete assignment of their (1)H, (13)C and (19)F NMR data was undertaken and the correlation of the chemical shifts of the ureido protons with field-inductive and mesomeric electronic substituent parameters was studied using the Swain-Lupton model. The best correlations were obtained when the study was limited to certain substitution patterns, e.g. non-ortho, mono-ortho- and di-ortho-fluorinated ureas, which reveal probable changes in conformations caused by the degree of ortho fluorination at the phenyl ring. Additionally, there is an excellent linear cross-correlation between the chemical shifts of the fluorine atoms and the ipso carbon atoms for the whole group of fluorinated ureas.

show abstract

Section: Resultsmentioning

confidence: 99%

¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

et al. 2005

View full text Add to dashboard Cite

show abstract

“…The f and r constants according to Swain and Lupton [24], [25], representing ®eld and resonance effects of the substituents were taken from [26]. To avoid the necessity of introducing parameters for each substituent position the f and r constants were multiplied with the corresponding weighting factors for the substituent position according to Williams and Norrington [27] (f: ortho 1.248, meta 0.980, para 1.000; r: ortho 0.863, meta 0.347, para 1.000).…”

Section: Qsar Methodsmentioning

confidence: 99%

QSAR Analysis of Substituted 2-Phenylhydrazonoacetamides Acting as Inhibitors of 15-Lipoxygenase

Fleischer

Frohberg

Büge

et al. 2000

Quant. Struct.-Act. Relat.

View full text Add to dashboard Cite

An evaluation of quantitative structure-activity relationships (QSAR) for 28 N 1 -phenyl-2-phenylhydrazonoacetamides, that are inhibitors of soybean 15-lipoxygenase was carried out with different statistical methods. Initially the variation of structure was characterized by the Free-Wilson method and analyzed by multiple linear regression (MLR) and partial least squares analysis (PLS). Both methods revealed an increase in activity, if the N 1 -phenyl substituent of the parent molecule is meta-substituted with groups, that show a positive resonance effect at the annular structure. To include physicochemical aspects a combined Free-Wilson-Hansch approach was used. Because of high intercorrelations among some physicochemical parameters a principal component-analysis (PCA) was performed to extract information from those intercorrelated variables in a few principal components (PC's). The resulting equations indicate that besides an electron donating group at the central amidrazone moiety electronic effects at the arylhydrazone substituent play an important role for the biological activity. * To receive all correspondence

show abstract

“…Furthermore, the substituents X (see Figure Table 1) were described by the two indicator variables I(OEt) and I(NH 2 ), i.e., for esters 1 -5 I(OEt) ¼ 1, I(NH 2 ) ¼ 0; for amides 5 -10 I(OEt) ¼ 0, I(NH 2 ) ¼ 1; and for acids 11 -15 I(OEt) ¼ 0, I(NH 2 ) ¼ 0, thus allowing a discrimination between the three subgroups of derivatives. The values p, f, and r (see Table 2) were taken from the literature [5,6]. To more adequately describe the electronic effect of substituents R' -R''' positional weighting factors f and r (see Table 3) for Sf and Sr, respectively, were applied [6,7].…”

Section: Compdmentioning

confidence: 99%

QSAR Analysis of the Time‐ and Dose‐Dependent Anti‐Inflammatory in vivo Activity of Substituted Imidazo[1,2‐a]pyridines Using Artificial Neural Networks

Saxena¹,

Schaper²

2006

QSAR Comb. Sci.

View full text Add to dashboard Cite

The quantitative analysis and physicochemical description of time-and dose-dependent in vivo drug effects is problematic as observed effects depend on both pharmacodynamics and pharmacokinetics. These factors depend in a different manner on the physicochemical properties of the investigated drugs. Obviously in vivo effects of drug series are governed by highly nonlinear relationships. As the function relating in vivo anti-inflammatory effects of the imidazo[1,2-a]pyridines observed in rats (carrageenan-induced rat paw edema test) to dose, time, and physicochemical properties could not be modeled explicitly, an attempt was made to train an Artificial Neural Network (ANN) to find the unknown nonlinear relationship between input variables and observed % effect values. The analysis extracted a maximum of information from available in vivo data and resulted in an ANN model that enabled the calculation of dose-and property-dependent antiinflammatory activities of a set of 15 imidazopyridines.

show abstract

Determination of positional weighting factors for the Swain and Lupton substituent constants f and r

Cited by 46 publications

References 13 publications

¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

QSAR Analysis of Substituted 2-Phenylhydrazonoacetamides Acting as Inhibitors of 15-Lipoxygenase

QSAR Analysis of the Time‐ and Dose‐Dependent Anti‐Inflammatory in vivo Activity of Substituted Imidazo[1,2‐a]pyridines Using Artificial Neural Networks

Contact Info

Product

Resources

About

Determination of positional weighting factors for the Swain and Lupton substituent constants f and r

Cited by 46 publications

References 13 publications

1H,13C and19F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

1H,13C and19F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

QSAR Analysis of Substituted 2-Phenylhydrazonoacetamides Acting as Inhibitors of 15-Lipoxygenase

QSAR Analysis of the Time‐ and Dose‐Dependent Anti‐Inflammatory in vivo Activity of Substituted Imidazo[1,2‐a]pyridines Using Artificial Neural Networks

Contact Info

Product

Resources

About

¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects

¹H,¹³C and¹⁹F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects