Quantitative structure–spectral property relationships for functional groups of novel 1,2,5-thiadiazole compounds

2011 ◽  
Vol 105 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Pablo R. Duchowicz ◽  
María V. Mirífico ◽  
María F. Rozas ◽  
José A. Caram ◽  
Francisco M. Fernández ◽  
...  
Keyword(s):  
Spectral Property ◽  
Functional Groups ◽  
Quantitative Structure

scholarly journals Retooling Asymmetric Conjugate Additions for Sterically Demanding Substrates with an Iterative Data-Driven Approach

2019 ◽  
Author(s):  
Alexandre Brethomé ◽  
Robert Paton ◽  
Stephen P. Fletcher
Keyword(s):  
Functional Groups ◽  
Conjugate Addition ◽  
Data Driven ◽  
Quantitative Structure ◽  
Conjugate Additions ◽  
Unsaturated Ketones ◽  
Alkyl Chains ◽  
Reaction Optimization ◽  
Sterically Demanding ◽  
Data Driven Approach

The development of new catalytic enantioselective methods is routinely carried out using easily accessible and prototypical substrates. This approach to reaction development often yields asymmetric methods that perform poorly using substrates sterically or electronically dissimilar to those used during the reaction optimization campaign. Consequently, expanding the scope of previously optimized catalytic asymmetric reactions to include new substrates is decidedly non-trivial. Here we address this challenge through the development of a systematic workflow to broaden the applicability and reliability of asymmetric conjugate additions to substrates conventionally regarded as sterically and electronically challenging. The copper-catalyzed asymmetric conjugate addition of alkylzirconium nucleophiles to form tertiary centers, although successful for linear alkyl chains, fails for more sterically demanding linear α,β-unsaturated ketones. Key to adapting this method to obtain high enantioselectivity was the discovery of new phosphoramidite ligands, designed using quantitative structure-selectivity relationships (QSSR). Iterative rounds of model construction and ligand synthesis were executed in parallel to evaluate the performance of twenty chiral ligands. The copper-catalyzed asymmetric addition is now more broadly applicable, even tolerating linear enones bearing tert-butyl β-substituents. The presence of common functional groups is tolerated in both nucleophiles and electrophiles, giving up to 99% yield and 95% ee across twenty examples.

scholarly journals Retooling Asymmetric Conjugate Additions for Sterically Demanding Substrates with an Iterative Data-Driven Approach

2019 ◽  
Author(s):  
Alexandre Brethomé ◽  
Robert Paton ◽  
Stephen P. Fletcher
Keyword(s):  
Functional Groups ◽  
Conjugate Addition ◽  
Data Driven ◽  
Quantitative Structure ◽  
Conjugate Additions ◽  
Unsaturated Ketones ◽  
Alkyl Chains ◽  
Reaction Optimization ◽  
Sterically Demanding ◽  
Data Driven Approach

The development of new catalytic enantioselective methods is routinely carried out using easily accessible and prototypical substrates. This approach to reaction development often yields asymmetric methods that perform poorly using substrates sterically or electronically dissimilar to those used during the reaction optimization campaign. Consequently, expanding the scope of previously optimized catalytic asymmetric reactions to include new substrates is decidedly non-trivial. Here we address this challenge through the development of a systematic workflow to broaden the applicability and reliability of asymmetric conjugate additions to substrates conventionally regarded as sterically and electronically challenging. The copper-catalyzed asymmetric conjugate addition of alkylzirconium nucleophiles to form tertiary centers, although successful for linear alkyl chains, fails for more sterically demanding linear α,β-unsaturated ketones. Key to adapting this method to obtain high enantioselectivity was the discovery of new phosphoramidite ligands, designed using quantitative structure-selectivity relationships (QSSR). Iterative rounds of model construction and ligand synthesis were executed in parallel to evaluate the performance of twenty chiral ligands. The copper-catalyzed asymmetric addition is now more broadly applicable, even tolerating linear enones bearing tert-butyl β-substituents. The presence of common functional groups is tolerated in both nucleophiles and electrophiles, giving up to 99% yield and 95% ee across twenty examples.

Improving integration between functional groups: A case in organization change and implications for theory and practice

1971 ◽  
Author(s):  
Warren G. Bennis ◽  
Michael Beer ◽  
Gerald R. Pieters ◽  
Alan T. Hundert ◽  
Samuel H. Marcus ◽  
...  
Keyword(s):  
Functional Groups ◽  
Organization Change ◽  
Theory And Practice

Seasonal variability in the quantitative structure of the digestive tubules ofLittorina littorea

1992 ◽  
Vol 5 (4) ◽  
pp. 299-305 ◽  
Author(s):  
lonan Marigómez ◽  
Manu Soto ◽  
Eduardo Angulo
Keyword(s):  
Seasonal Variability ◽  
Quantitative Structure

HYDROXYAPATITE, ALGINATE, AND CHITOSAN FOR BONE SCAFFOLDS: SPECTROSCOPY STUDY

2016 ◽  
Vol 19 (2) ◽  
pp. 93-100
Author(s):  
Lalita El Milla
Keyword(s):  
Tissue Engineering ◽  
Bone Tissue Engineering ◽  
Bone Tissue ◽  
Functional Groups ◽  
Bone Growth ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Tissue Engineering Scaffolds ◽  
Hydroxyapatite Powder ◽  
Materials Used

Scaffolds is three dimensional structure that serves as a framework for bone growth. Natural materials are often used in synthesis of bone tissue engineering scaffolds with respect to compliance with the content of the human body. Among the materials used to make scafffold was hydroxyapatite, alginate and chitosan. Hydroxyapatite powder obtained by mixing phosphoric acid and calcium hydroxide, alginate powders extracted from brown algae and chitosan powder acetylated from crab. The purpose of this study was to examine the functional groups of hydroxyapatite, alginate and chitosan. The method used in this study was laboratory experimental using Fourier Transform Infrared (FTIR) spectroscopy for hydroxyapatite, alginate and chitosan powders. The results indicated the presence of functional groups PO43-, O-H and CO32- in hydroxyapatite. In alginate there were O-H, C=O, COOH and C-O-C functional groups, whereas in chitosan there were O-H, N-H, C=O, C-N, and C-O-C. It was concluded that the third material containing functional groups as found in humans that correspond to the scaffolds material in bone tissue engineering.

Climate resilience through natural regeneration in degraded natural forests of south-eastern hilly region of Bangladesh

2019 ◽  
Vol 48 (3) ◽  
pp. 417-425
Author(s):  
Md Khayrul Alam Bhuiyan ◽  
Md Akhter Hossain ◽  
Abdul Kadir Ibne Kamal ◽  
Mohammed Kamal Hossain ◽  
Mohammed Jashimuddin ◽  
...  
Keyword(s):  
Tree Species ◽  
Natural Regeneration ◽  
Diversity Indices ◽  
Acacia Auriculiformis ◽  
Quantitative Structure ◽  
Natural Forests ◽  
Climate Resilience ◽  
Hilly Region ◽  
Major Cluster ◽  
Ecological Dominance

A study was conducted by using 5m × 5m sized 179 quadrates following multistage random sampling method for comparative regenerating tree species, quantitative structure, diversity, similarity and climate resilience in the degraded natural forests and plantations of Cox's Bazar North and South Forest Divisions. A total of 70 regenerating tree species were recorded representing maximum (47 species) from degraded natural forests followed by 43 species from 0.5 year 39 species from 1.5 year and 29 species from 2.5 year old plantations. Quantitative structure relating to ecological dominance indicated dominance of Acacia auriculiformis, Grewia nervosa and Lithocarpus elegans seedlings in the plantations whereas seedlings of Aporosa wallichii, Suregada multiflora and Grewia nervosa in degraded natural forests. The degraded natural forests possess higher natural regeneration potential as showed by different diversity indices. The dominance-based cluster analysis showed 2 major cluster of species under one of which multiple sub-clusters of species exists. Poor plant diversity and presence of regenerating exotic species in the plantations indicated poor climate resilience of forest ecosystem in terms of natural regeneration.

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