The Use of Linear Free Energy Parameters and Other Experimental Constants in Structure–Activity Studies

Verloop, A.

doi:10.1016/b978-0-12-060303-9.50008-2

Cited by 21 publications

(6 citation statements)

References 108 publications

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“…QSAR analysis is not necessarily a causal analysis, but rather is the search of phenomenological correlations that fit and are adequate to search new active compounds. The extraction of mechanistic conclusions from other QSAR analyses, such as the Hansch approach, has been criticized, although these kinds of descriptors have a priori precise meanings and easy interpretation.…”

Section: Methods Results and Discussionmentioning

confidence: 99%

Antimicrobial Activity Characterization in a Heterogeneous Group of Compounds

García-Domènech

Julián-Ortiz

1998

J. Chem. Inf. Comput. Sci.

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In this work we carry out a study of pattern recognition to detect the microbiological activity in a group of heterogeneous compounds. The structural descriptors utilized are the topological connectivity indexes. The methods followed are stepwise linear discriminant analysis (linear analysis) and artificial neural network (nonlinear analysis). Although both methods are appropriate to differentiate between active and inactive compounds, the artificial neural network is, in this case, more adequate, since it shows in a test set a prediction success of 98%, versus 92% obtained with linear discriminant analysis.

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Section: Methods Results and Discussionmentioning

confidence: 99%

Antimicrobial Activity Characterization in a Heterogeneous Group of Compounds

García-Domènech

Julián-Ortiz

1998

J. Chem. Inf. Comput. Sci.

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“…For the X 8 TPP complexes and for a given metal ion, E sadd – E ruff exhibits a strong, linear dependence on the steric bulk of the β substituent X, as measured by either the Charton − or the Sterimol B 1 − parameters (Figure ), with one key exception, X = Ph. Thus, the preference for the saddled conformation relative to the ruffled conformation ranges from about ∼0.3–0.4 eV for Me 8 TPP derivatives up to 1 eV for I 8 TPP and (CF 3 ) 8 TPP derivatives.…”

Section: Resultsmentioning

confidence: 99%

Energetics of Saddling versus Ruffling in Metalloporphyrins: Unusual Ruffled Dodecasubstituted Porphyrins

Conradie

Ghosh

2017

ACS Omega

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Presented herein is a first major density functional theory (BP86/D3/STO-TZ2P) survey of the energetics of saddling versus ruffling for a wide range of dodecasubstituted metalloporphyrins with M = Ni, Cu, Zn, Pd, and Pt. For the majority of X 8 TPP (i.e., β-octasubstituted- meso -tetraphenylporphyrin), the calculations indicated a clear preference for the saddled conformation, consistent with a large body of experimental data. The preference for the saddled conformation relative to the ruffled conformation was found to vary from about ∼0.3–0.4 eV for Me 8 TPP derivatives up to 1 eV for I 8 TPP and (CF 3 ) 8 TPP derivatives. For X = Ph, that is, dodecaphenylporphyrins, the saddled and the ruffled conformation are almost equienergetic, with even a slight preference for the ruffled conformation in some cases. This finding provides a satisfactory explanation for the X-ray crystallographic observation of both saddled and ruffled conformations for dodecaphenylporphyrin complexes as well as for spectroscopic evidence for conformational mobility of these complexes in solution. The calculations also indicate near-equienergetic saddled and ruffled conformations for meso -tetraacetylenyltetrabenzoporphyrins, again consonant with key crystallographic findings. By and large, both the energetics and nonplanar distortions of the metalloporphyrin derivatives correlated well with the Charton and Sterimol B 1 steric parameters of the peripheral substituents.

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“…We found that diastereoselectivity can be quantified using steric descriptors (Charton, Sterimol) either for the substrate substituents or for the catalyst substituents. , We also observed that the site selectivity for [Ir–H] insertion can be reversed leading to the formation of homoallylic alcohols preferentially over aldehydes when sterically demanding iridium catalysts are employed.…”

Section: Iridium-catalyzed Isomerization Of Allylic Alcoholsmentioning

confidence: 99%

Iridium-Catalyzed Selective Isomerization of Primary Allylic Alcohols

Mazet

2016

Acc. Chem. Res.

102

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This Account presents the development of the iridium-catalyzed isomerization of primary allylic alcohols in our laboratory over the past 8 years. Our initial interest was driven by the long-standing challenge associated with the development of a general catalyst even for the nonasymmetric version of this seemingly simple chemical transformation. The added value of the aldehyde products and the possibility to rapidly generate molecular complexity from readily accessible allylic alcohols upon a redox-economical isomerization reaction were additional sources of motivation. Certainly influenced by the success story of the related isomerization of allylic amines, most catalysts developed for the selective isomerization of allylic alcohols were focused on rhodium as a transition metal of choice. Our approach has been based on the commonly accepted precept that hydrogenation and isomerization are often competing processes, with the latter being usually suppressed in favor of the former. The cationic iridium complexes [(Cy3P)(pyridine)Ir(cod)]X developed by Crabtree (X = PF6) and Pfaltz (X = BArF) are usually considered as the most versatile catalysts for the hydrogenation of allylic alcohols. Using molecular hydrogen to generate controlled amounts of the active form of these complexes but performing the reaction in the absence of molecular hydrogen enabled deviation from the typical hydrogenation manifold and favored exclusively the isomerization of allylic alcohols into aldehydes. Isotopic labeling and crossover experiments revealed the intermolecular nature of the process. Systematic variation of the ligand on the iridium center allowed us to identify the structural features beneficial for catalytic activity. Subsequently, three generations of chiral catalysts have been investigated and enabled us to reach excellent levels of enantioselectivity for a wide range of 3,3-disubstituted aryl/alkyl and alkyl/alkyl primary allylic alcohols leading to β-chiral aldehydes. The combination of the isomerization reaction with enamine catalysis in a sequential process gave access to α,β-chiral aldehydes in high diastereomeric ratio and excellent enantioselectivity. Catalyst-controlled diastereoselective isomerization of stereochemically complex steroid scaffolds has been achieved, giving access indifferently to derivatives with the natural and unnatural C20 configuration, a long-standing challenge in the field. Structural diversification at close proximity of the reactive site and within the polycyclic domain served to further demonstrate the generality and the potential of the method. Models based on quadrant diagrams enabled rationalization of the high levels of enantio- and diastereocontrol obtained in the isomerization of allylic alcohols.

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The Use of Linear Free Energy Parameters and Other Experimental Constants in Structure–Activity Studies

Cited by 21 publications

References 108 publications

Antimicrobial Activity Characterization in a Heterogeneous Group of Compounds

Antimicrobial Activity Characterization in a Heterogeneous Group of Compounds

Energetics of Saddling versus Ruffling in Metalloporphyrins: Unusual Ruffled Dodecasubstituted Porphyrins

Iridium-Catalyzed Selective Isomerization of Primary Allylic Alcohols

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