Thermodynamics of the Dissolution of Asymmetric Macroheterocyclic Compounds with Thiadiazol Fragments in Polar Solvents

2021 ◽  
Vol 95 (6) ◽  
pp. 1152-1155
Author(s):  
G. R. Berezina
Keyword(s):  
Polar Solvents ◽  
Macroheterocyclic Compounds

Tele-Substitution Reactions in the Synthesis of a Promising Class of Antimalarials

2020 ◽  
Author(s):  
Marat Korsik ◽  
Edwin Tse ◽  
David Smith ◽  
William Lewis ◽  
Peter J. Rutledge ◽  
...  
Keyword(s):  
Heterocyclic Ring ◽  
Ring System ◽  
Substitution Reactions ◽  
Laboratory Notebook ◽  
Polar Solvents ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Core ◽  
Nmr Data

<p></p><p>We have discovered and studied a <i>tele</i>substitution reaction in a biologically important heterocyclic ring system. Conditions that favour the <i>tele</i>-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base, or the use of softer nucleophiles, less polar solvents and larger halogens on the electrophile. Using results from X-ray crystallography and isotope labelling experiments a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the <i>in vivo </i>active anti-plasmodium compounds of Series 4 of the Open Source Malaria consortium.</p> <p> </p> <p>Archive of the electronic laboratory notebook with the description of all conducted experiments and raw NMR data could be accessed via following link <a href="https://ses.library.usyd.edu.au/handle/2123/21890">https://ses.library.usyd.edu.au/handle/2123/21890</a> . For navigation between entries of laboratory notebook please use file "Strings for compounds in the article.pdf" that works as a reference between article codes and notebook codes, also this file contain SMILES for these compounds. </p><br><p></p>

Stereospecific 1,3-H Transfer of Indenols Proceeds via Persistent Ion-Pairs Anchored By NH···Pi Interactions

2018 ◽  
Author(s):  
David Ascough ◽  
Fernanda Duarte ◽  
Robert Paton
Keyword(s):  
Computational Analysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Chirality Transfer ◽  
Activation Barriers ◽  
Sense And Avoid ◽  
Phase Dynamics ◽  
Pi Interactions

The base-catalyzed rearrangement of arylindenols is a rare example of a suprafacial [1,3]-hydrogen atom transfer. The mechanism has been proposed to proceed via sequential [1,5]-sigmatropic shifts, which occur in a selective sense and avoid an achiral intermediate. A computational analysis using quantum chemistry casts serious doubt on these suggestions: these pathways have enormous activation barriers and in constrast to what is observed experimentally, they overwhelmingly favor a racemic product. Instead we propose that a suprafacial [1,3]-prototopic shift occurs in a two-step deprotonation/reprotonation sequence. This mechanism is favored by 15 kcal mol<sup>-1</sup> over that previously proposed. Most importantly, this is also consistent with stereospecificity since reprotonation occurs rapidly on the same p-face. We have used explicitly-solvated molecular dynamics studies to study the persistence and condensed-phase dynamics of the intermediate ion-pair formed in this reaction. Chirality transfer is the result of a particularly resilient contact ion-pair, held together by electrostatic attraction and a critical NH···p interaction which ensures that this species has an appreciable lifetime even in polar solvents such as DMSO and MeOH.

Understanding Process Variables and their Interactions for Maximizing Production of Artemisinin Derivative Artemether (Anti-Malarial Drug) Through Cunninghamella echinulata var elegans at 5 L Bioreactor Level

2019 ◽  
Vol 15 (4) ◽  
pp. 442-452
Author(s):  
Kashyap Kumar Dubey ◽  
Punit Kumar
Keyword(s):  
Experimental Finding ◽  
Culture Broth ◽  
Quadratic Model ◽  
Optimum Conditions ◽  
Reverse Phase Hplc ◽  
Polar Solvents ◽  
Reverse Phase ◽  
Experimental Conditions ◽  
Cunninghamella Echinulata ◽  
Life Threatening

Background: Malaria is one of the life threatening diseases which is caused by Plasmodium sp. of protozoa and uses Anopheles mosquitos as vector. Plasmodium vivax and Plasmodium falciparum are common form of malaria parasite. Artemisinin is reported for its antimalarial activities and Artemether which is a methyl ether derivative of Artemisinin, has been found effective against P. falciparum. Methods: In the present study, bioconversion of Artemisinin into Artemether was carried out experimentally and the statistical tools like experimental factorial design and Response Surface Methodology were used to find optimal conditions (concentration of Artemisinin, age of inoculum, temperature & pH) using Cunninghamella echinulata var. elegans. Experimental conditions for maximum product recovery from culture broth were also optimized using various polar and non-polar solvents for extraction. Artemether purity was analyzed by reverse-phase HPLC. Experimental data was fitted in a quadratic model and effect of various parameters was analyzed. Results: It was found that bioconversion of Artemisinin into Artemether is growth associated process. It was observed that molasses used as carbon source supported production of Artemether to 3.4g/L. The biomass and oxygen are key element affecting of bioconversion of Artemisinin into Artemether such as higher dissolved oxygen reduced the Artemether bioconversion. The highest bioconversion of Artemisinin into Artemether was obtained at temperature 25.5oC, 5g/L concentration of Artemisinin, at age of inoculum of 44.5 h and at pH 6.0. Model suggested the highest bioconversion of Artemisinin into Artemether was 54% at shake flask level which was near about experimental finding. An optimal condition for bioconversion was also analyzed and 64% bioconversion was obtained in 5L bioreactor. Conclusion: The outcomes of the study provided optimum conditions for bioconversion of Artemisinin into Artemether.

Infrared spectra of N-acetyl-L-α-amino-acid N'-methylamides with aliphatic side chains in non-polar solvents

1981 ◽  
Vol 46 (3) ◽  
pp. 772-780 ◽  
Author(s):  
Jorga Smolíková ◽  
Jan Pospíšek ◽  
Karel Bláha
Keyword(s):  
Amino Acid ◽  
Conformational Changes ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Side Chains ◽  
Polar Solvents

Infrared spectra of the L-alanine (I), L-leucine (II), L-valine (III) and L-tert-leucine (IV) N-acetyl N'-methylamides were measured. Amides I-IV are not self associated in tetrachlormethane in the concentration 2 . 10-5 mol l-1 at room temperature and in tetrachloroethylene in the concentration 1.5 . 10-4 mol l-1 at temperatures above 65° C. True conformational changes are observable only with the least flexible amide IV which exists at room temperature in a C5 conformation. This conformational type is also highly populated in the valine derivative III, but is less important in the alanine and leucine derivatives I and II in which the intramolecularly bonded C7 and the distorted hydrogen-nonbonded conformations contribute seriously.

Solvation and redox properties of [Co(en)3]3+-[Co(en)3]2+ system

1980 ◽  
Vol 45 (2) ◽  
pp. 335-338 ◽  
Author(s):  
Adéla Kotočová ◽  
Ulrich Mayer
Keyword(s):  
Hydrogen Bond ◽  
Lewis Acid ◽  
Specific Interaction ◽  
Redox Properties ◽  
Solvation Effect ◽  
Interacting Particles ◽  
Acid Base ◽  
Polar Solvents ◽  
Oxidation Reduction ◽  
Solvent Molecules

The solvation effect of a number of nonaqueous polar solvents was studied on the oxidation-reduction properties of the [Co(en)3]3+-[Co(en)3]2+ system. Interactions of these ions with the solvent molecules are discussed in terms of their coordination, which is accompanied by a specific interaction of the Lewis acid-base type, namely formation of a hydrogen bond between the interacting particles. This is the main controlling factor of the redox properties of the studied system.

scholarly journals Graphene Oxide: A Smart (Starting) Material for Natural Methylxanthines Adsorption and Detection

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4247 ◽  
Author(s):  
Rita Petrucci ◽  
Isabella Chiarotto ◽  
Leonardo Mattiello ◽  
Daniele Passeri ◽  
Marco Rossi ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Graphene Oxide ◽  
Nucleic Acids ◽  
Reduced Graphene Oxide ◽  
Electrochemical Sensors ◽  
Enzymatic Digestion ◽  
Biologically Active ◽  
Polar Solvents ◽  
Dna And Rna ◽  
Reduced Graphene

Natural methylxanthines, caffeine, theophylline and theobromine, are widespread biologically active alkaloids in human nutrition, found mainly in beverages (coffee, tea, cocoa, energy drinks, etc.). Their detection is thus of extreme importance, and many studies are devoted to this topic. During the last decade, graphene oxide (GO) and reduced graphene oxide (RGO) gained popularity as constituents of sensors (chemical, electrochemical and biosensors) for methylxanthines. The main advantages of GO and RGO with respect to graphene are the easiness and cheapness of synthesis, the notable higher solubility in polar solvents (water, among others), and the higher reactivity towards these targets (mainly due to – interactions); one of the main disadvantages is the lower electrical conductivity, especially when using them in electrochemical sensors. Nonetheless, their use in sensors is becoming more and more common, with the obtainment of very good results in terms of selectivity and sensitivity (up to 5.4 × 10−10 mol L−1 and 1.8 × 10−9 mol L−1 for caffeine and theophylline, respectively). Moreover, the ability of GO to protect DNA and RNA from enzymatic digestion renders it one of the best candidates for biosensors based on these nucleic acids. This is an up-to-date review of the use of GO and RGO in sensors.

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