scholarly journals Spontaneous Resolution in Racemic Solutions of N-trifluoroacetylated α-aminoalcohols

2018 ◽  
Author(s):  
Dmitry V Zlenko ◽  
Anatoly Zanin ◽  
Aleksey Skoblin ◽  
Vsevolod Tverdislov ◽  
Sergey Stovbun
Keyword(s):  
Living Cell ◽  
Enantiomeric Excess ◽  
Spontaneous Resolution ◽  
Crystalline Structures ◽  
Chiral Purity

The spontaneous resolution was observed in the racemic solution of N-trifluoroacetylated α-aminoalcohol (TFAAA-6) in CCl4. In against other cases of the conglomerates formation, the TFAAA-6 forms highly anisometric crystalline structures (strings). Herewith, the spontaneous resolution was not observed in the racemic solution of TFAAA-5 in heptane, where the isometric precipitate was formed. The latter was also observed in the TFAAA-5 solutions in heptane with small enantiomeric excess (EE), down to 2 %. With that, the homochiral strings formed in the TFAAA-5 solutions in heptane with larger EEs. In this case, the strings formed from the excess of one of the enantiomers remained in solution after precipitation of the racemic residual. This process leads to the enhancement of chiral polarization in systems close to racemic and can explain the chiral purity of the living cell.

Revival of the concept of the cold prehistory of life

1993 ◽  
Vol 1 (2) ◽  
pp. 137-147 ◽  
Author(s):  
Vitalii I. Goldanskii
Keyword(s):  
Origin Of Life ◽  
Mirror Symmetry ◽  
Solid Phase ◽  
Outer Space ◽  
Enantiomeric Excess ◽  
Quantum Limit ◽  
Spontaneous Breaking ◽  
Quasi Equilibrium ◽  
Chiral Purity ◽  
The Origin Of Life

The extra-terrestrial scenario of the origin of life suggested by Svante Arrhenius (1908) as the ‘panspermia’ hypothesis was revived by the discovery of a low-temperature quantum limit of a chemical reaction rate in 1973. Entropy factors play no role near absolute zero, and slow molecular tunnelling can lead to the exothermic formation of quite complex molecules. Interstellar grains or particles of cometary tails could serve as possible cold seeds of life, with acetic acid, urea and products of their polycondensation as quasi-equilibrium intermediates. Scenarios of the origin of life should consider the appearance of a typical feature of living species—chiral purity of their aminoacids and sugars. Very cold solid environment hinders tunnelling racemization under conditions typical for outer space. However, the decisive problem of the origin of chiral purity of the Earth's biosphere is the mechanism of the spontaneous breaking of mirror symmetry rather than the search for some ‘advantage factors’ which can promote gradual accumulation of enantiomeric excess. Extra-terrestrial (cold, solid phase) scenarios of the origin of life seem to be more promising from that point of view than terrestrial (warm) scenarios. In a scheme of five main stages of prebiological evolution some problems important for further investigation are briefly discussed.

Intranuclear Crystals in Regenerating Canine Kidneys

1973 ◽  
Vol 31 ◽  
pp. 412-413
Author(s):  
D.G. Osborne ◽  
L.J. McCormack ◽  
M.O. Magnusson ◽  
W.S. Kiser
Keyword(s):  
Epithelial Cell ◽  
Epithelial Cells ◽  
Tubular Epithelial Cell ◽  
Tubular Epithelial Cells ◽  
Cell Nuclei ◽  
Crystalline Structures ◽  
Small Crystals ◽  
Membrane Bound

During a project in which regenerative changes were studied in autotransplanted canine kidneys, intranuclear crystals were seen in a small number of tubular epithelial cells. These crystalline structures were seen in the control specimens and also in regenerating specimens; the main differences being in size and number of them. The control specimens showed a few tubular epithelial cell nuclei almost completely occupied by large crystals that were not membrane bound. Subsequent follow-up biopsies of the same kidneys contained similar intranuclear crystals but of a much smaller size. Some of these nuclei contained several small crystals. The small crystals occurred at one week following transplantation and were seen even four weeks following transplantation. As time passed, the small crystals appeared to fuse to form larger crystals.

Solving the mechanisms responsible for organelle behavior in vivo by same-cell correlative light and electron microscopy

1992 ◽  
Vol 50 (1) ◽  
pp. 14-15
Author(s):  
Conly L. Rieder
Keyword(s):  
Electron Microscopy ◽  
Quantitative Analysis ◽  
Light Microscopy ◽  
Living Cell ◽  
Light And Electron Microscopy ◽  
Time Behavior ◽  
Dynamic Interactions ◽  
Positive Identification ◽  
Cellular Components

The behavior of many cellular components, and their dynamic interactions, can be characterized in the living cell with considerable spatial and temporal resolution by video-enhanced light microscopy (video-LM). Indeed, under the appropriate conditions video-LM can be used to determine the real-time behavior of organelles ≤ 25-nm in diameter (e.g., individual microtubules—see). However, when pushed to its limit the structures and components observed within the cell by video-LM cannot be resolved nor necessarily even identified, only detected. Positive identification and a quantitative analysis often requires the corresponding electron microcopy (EM).

A Case of Spontaneous Resolution of Castleman's Disease in the Neck

2012 ◽  
Vol 55 (11) ◽  
pp. 736
Author(s):  
Seong-Hyun Yun ◽  
Soo-Ryang Chae ◽  
Dong-Joon Yoo ◽  
Young-Hoon Joo
Keyword(s):  
Castleman’S Disease ◽  
Spontaneous Resolution ◽  
Castleman's Disease

Spontaneous resolution of hypothalamic amenorrhea post diagnostic GnRH test

2015 ◽  
Author(s):  
G K Dimitriadis ◽  
M O Weickert ◽  
T M Barber ◽  
H S Randeva
Keyword(s):  
Spontaneous Resolution ◽  
Hypothalamic Amenorrhea

Room Temperature Flow Electrochemistry as a Means of Retaining the “Memory of Chirality” via Hofer Moest Type Reaction

2020 ◽  
Author(s):  
Tomas Hardwick ◽  
Rossana Cicala ◽  
Nisar Ahmed
Keyword(s):  
Continuous Flow ◽  
Room Temperature ◽  
Biological Activities ◽  
Supporting Electrolyte ◽  
Enantiomeric Excess ◽  
Flow Chemistry ◽  
Batch Processes ◽  
Enabling Technology ◽  
Chiral Compounds ◽  
Memory Of Chirality

<p>Many chiral compounds have become of great interest to the pharmaceutical industry as they possess various biological activities. Concurrently, the concept of “memory of chirality” has been proven as a powerful tool in asymmetric synthesis, while flow chemistry has begun its rise as a new enabling technology to add to the ever increasing arsenal of techniques available to the modern day chemist. Here, we have employed a new simple electrochemical microreactor design to oxidise an L-proline derivative at room temperature in continuous flow. Flow performed in microreactors offers up a number of benefits allowing reactions to be performed in a more convenient and safer manner, and even allow electrochemical reactions to take place without a supporting electrolyte due to a very short interelectrode distance. By the comparison of electrochemical oxidations in batch and flow we have found that continuous flow is able to outperform its batch counterpart, producing a good yield (71%) and a better enantiomeric excess (64%) than batch with a 98% conversion. We have, therefore, provided evidence that continuous flow chemistry has the potential to act as a new enabling technology to replace some aspects of conventional batch processes. </p>

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