scholarly journals Pre-regulation of the planar chirality of pillar[5]arenes for preparing discrete chiral nanotubes

2021 ◽  
Vol 12 (10) ◽  
pp. 3483-3488
Author(s):  
Shixin Fa ◽  
Keisuke Adachi ◽  
Yuuya Nagata ◽  
Kouichi Egami ◽  
Kenichi Kato ◽  
...  
Keyword(s):  
Building Blocks ◽  
Planar Chirality ◽  
Chiral Nanotubes ◽  
Chiral Nanotube

Pillar[5]arene-based chiral nanotube formation via pre-regulation of the building blocks' chirality is more efficient than post-regulating the chirality of nanotubes.

scholarly journals SYNTHESIS OF A 1,2,3-TRIAZOLE-CONTAINING MACROCYCLE BASED ON THE "CLICK CHEMISTRY" REACTION AND ANALYSIS OF ITS PLANAR CHIRALITY USING NMR AND DFT CALCULATIONS

2020 ◽  
pp. 55-61
Author(s):  
H. Yampolska ◽  
S. Kharchenko ◽  
A. Kozytskyi ◽  
A. Kyrylchuk ◽  
Z. Voitenko ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Click Chemistry ◽  
Protein Interactions ◽  
Variable Temperature ◽  
Triazole Ring ◽  
Building Blocks ◽  
Ring Closure ◽  
Amide Bond ◽  
High Yield ◽  
Planar Chirality

Macrocycles represent previously unexplored promising drug candidates, that can be useful for treating protein-protein interactions. Atropoisomerism is an inherent feature of the natural macrocyclic peptides that is significant for their activity and selectivity, and, therefore, should be introduced into newly synthesized macrocycles. Synthesis of the libraries of artificial macrocycles faces many challenges due to their structure and size. Herein we report on the preparation of a 16-membered macrocycle containing 1,2,3-triazole ring, spiro-piperidine, and phenyl moieties, as well as a chiral carbon atom. Our approach to the macrocycle was inspired by the "build/couple/pair" (B/C/P) strategy, a part of diversity-oriented synthesis methodology. We have employed readily accessible starting materials and robust synthetic procedures which allowed us to obtain the target macrocycle in a high yield. Standard methods of amide bond formation were used for the coupling of macrocycle building blocks. Click chemistry azide-alkyne cycloaddition was exploited at the final ring closure step. The assignment of signals in 1H and 13C NMR spectra of the macrocycle was performed using a series of 2D NMR techniques. The macrocycle displayed planar chirality, which, in a combination with a stereocenter with the known configuration, was sufficient to propose possible structures of diastereomers. The diastereomers could differ by the relative position of triazole ring. Their racemization could occur through a "rope skipping" motion involving the cyclic chain crossing the plane of 1,2,3-triazole ring. The supposed structures of diastereomers were corroborated by means of a various NMR spectroscopy techniques and DFT calculations. Analysis of the amide NH chemical shift temperature coefficients coupled with the data on optimized geometries obtained by DFT convincingly demonstrated that the intramolecular hydrogen bonds play a major role in stabilization of the diastereomer structures. According to the variable temperature NMR experiment, the interconversion of two diastereomers did not occur even at heating up to 70 °C.

Biocatalytic synthesis of planar chiral macrocycles

Science ◽  
2020 ◽  
Vol 367 (6480) ◽  
pp. 917-921 ◽  
Author(s):  
Christina Gagnon ◽  
Éric Godin ◽  
Clémentine Minozzi ◽  
Johann Sosoe ◽  
Corentin Pochet ◽  
...  
Keyword(s):  
Building Blocks ◽  
Structural Features ◽  
Synthetic Methods ◽  
Planar Chirality ◽  
Chiral Macrocycles

Macrocycles can restrict the rotation of substituents through steric repulsions, locking in conformations that provide or enhance the activities of pharmaceuticals, agrochemicals, aroma chemicals, and materials. In many cases, the arrangement of substituents in the macrocycle imparts an element of planar chirality. The difficulty in predicting when planar chirality will arise, as well as the limited number of synthetic methods to impart selectivity, have led to planar chirality being regarded as an irritant. We report a strategy for enantio- and atroposelective biocatalytic synthesis of planar chiral macrocycles. The macrocycles can be formed with high enantioselectivity from simple building blocks and are decorated with functionality that allows one to further modify the macrocycles with diverse structural features.

Ab Inito Study of Absorption Spectra in Ultra Small Diameter Single Walled Boron Nanotubes

2011 ◽  
Vol 217-218 ◽  
pp. 16-20
Author(s):  
Sandeep Kumar Jain ◽  
Pankaj Srivastava
Keyword(s):  
Absorption Spectra ◽  
Polarized Light ◽  
Small Diameter ◽  
Unpolarized Light ◽  
Wide Range ◽  
Chiral Nanotubes ◽  
Ab Inito ◽  
Chiral Nanotube

We have investigated the absorption spectra in ultra small diameter single walled boron nanotubes for parallel and perpendicular polarized light as well as unpolarized light. In this paper we have studied absorption spectra for armchair (3,3),zigzag (5,0) and chiral (4,2) boron nanotubes containing 12, 20 and 56 atoms respectively. It is observed that absorption is highest for armchair followed by zigzag and chiral nanotubes. It is also found that absorption is higher for (3,3) and (5,0) nanotubes for perpendicular polarized light as compared to parallel polarized light, whereas chiral nanotube shows higher and wide range of absorption for parallel polarized light instead of perpendicular polarized light. We have compared our results with SWCNT and SWBNNT of same chiral vectors.

Photochemical Evolution of Interstellar/Precometary Organic Material

1997 ◽  
Vol 161 ◽  
pp. 23-47 ◽  
Author(s):  
Louis J. Allamandola ◽  
Max P. Bernstein ◽  
Scott A. Sandford
Keyword(s):  
Origin Of Life ◽  
Building Blocks ◽  
Complex Species ◽  
Infrared Observations ◽  
Interstellar Ice ◽  
Polycyclic Aromatic ◽  
Ultraviolet Photolysis ◽  
The Origin Of Life ◽  
Simple Molecules ◽  
Complex Organic

AbstractInfrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Since comets are thought to be a major source of the volatiles on the primative earth, their organic inventory is of central importance to questions concerning the origin of life. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, CH4, H2, and probably some NH3and H2CO, as well as more complex species including nitriles, ketones, and esters. The evidence for these, as well as carbonrich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon is briefly reviewed. This is followed by a detailed summary of interstellar/precometary ice photochemical evolution based on laboratory studies of realistic polar ice analogs. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(= O)NH2(formamide), CH3C(= O)NH2(acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including polyoxymethylene and related species (POMs), amides, and ketones. The ready formation of these organic species from simple starting mixtures, the ice chemistry that ensues when these ices are mildly warmed, plus the observation that the more complex refractory photoproducts show lipid-like behavior and readily self organize into droplets upon exposure to liquid water suggest that comets may have played an important role in the origin of life.

Laboratory and in-situ analysis of comet dust

1988 ◽  
Vol 46 ◽  
pp. 8-9
Author(s):  
D.E. Brownlee ◽  
A.L. Albee
Keyword(s):  
Electron Microscopy ◽  
Solar System ◽  
Laboratory Study ◽  
Isotopic Analysis ◽  
Building Blocks ◽  
Sem Analysis ◽  
Early Solar System ◽  
Cometary Material ◽  
Comet Dust

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.

Cryo-TEM of amphiphilic polymer and amphiphile/polymer solutions

1993 ◽  
Vol 51 ◽  
pp. 876-877
Author(s):  
Yeshayahu Talmon
Keyword(s):  
Microstructural Characterization ◽  
Building Blocks ◽  
Quantitative Information ◽  
Physical Models ◽  
Specimen Preparation ◽  
Time Resolved ◽  
Temperature Changes ◽  
Temperature And Humidity ◽  
Microstructured Fluids ◽  
Air Streams

To achieve complete microstructural characterization of self-aggregating systems, one needs direct images in addition to quantitative information from non-imaging, e.g., scattering or Theological measurements, techniques. Cryo-TEM enables us to image fluid microstructures at better than one nanometer resolution, with minimal specimen preparation artifacts. Direct images are used to determine the “building blocks” of the fluid microstructure; these are used to build reliable physical models with which quantitative information from techniques such as small-angle x-ray or neutron scattering can be analyzed.To prepare vitrified specimens of microstructured fluids, we have developed the Controlled Environment Vitrification System (CEVS), that enables us to prepare samples under controlled temperature and humidity conditions, thus minimizing microstructural rearrangement due to volatile evaporation or temperature changes. The CEVS may be used to trigger on-the-grid processes to induce formation of new phases, or to study intermediate, transient structures during change of phase (“time-resolved cryo-TEM”). Recently we have developed a new CEVS, where temperature and humidity are controlled by continuous flow of a mixture of humidified and dry air streams.

Emotional Variability Predicts Tiredness in Daily Life

2016 ◽  
Vol 37 (3) ◽  
pp. 181-193 ◽  
Author(s):  
Aire Mill ◽  
Anu Realo ◽  
Jüri Allik
Keyword(s):  
Sampling Method ◽  
Daily Life ◽  
Emotional Experience ◽  
Experience Sampling ◽  
Experience Sampling Method ◽  
Building Blocks ◽  
Intraindividual Variability ◽  
Unique Role ◽  
Over Time

Abstract. Intraindividual variability, along with the more frequently studied between-person variability, has been argued to be one of the basic building blocks of emotional experience. The aim of the current study is to examine whether intraindividual variability in affect predicts tiredness in daily life. Intraindividual variability in affect was studied with the experience sampling method in a group of 110 participants (aged between 19 and 84 years) during 14 consecutive days on seven randomly determined occasions per day. The results suggest that affect variability is a stable construct over time and situations. Our findings also demonstrate that intraindividual variability in affect has a unique role in predicting increased levels of tiredness at the momentary level as well at the level of individuals.

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