Science topic

Asymmetric Synthesis - Science topic

Explore the latest questions and answers in Asymmetric Synthesis, and find Asymmetric Synthesis experts.
Questions related to Asymmetric Synthesis
  • asked a question related to Asymmetric Synthesis
Question
16 answers
A reaction of A and B, gives C. the NMR of reaction mixture contain all peaks of A,B,C. I need to calculate yield or percentage conversion of B to C. A has no role . Yield of C need to calculate with respect to B. all have distinguish peaks. On integration, specific peak of C has 1.00 while B has 0.35. both contain 2 hydrogens each. Can I say yield of C is 1/1.35 *100= 74% ? Or is there any other methods to calculate the yield ?
Relevant answer
Answer
Carlos F. Marcos
- ERETIC2 and QUANTAS are both software approaches based on the PULCON method of Wider et al. (J Am Chem Soc. 2006 Mar 1;128(8):2571-6. doi: 10.1021/ja055336t). Note that the original ERETIC (Akoka et al.) is a hardware-based approach and may not be suitable. QUANTAS reference: Magn Reson Chem. 2010 Oct;48(10):753-62. doi: 10.1002/mrc.2647. PMID: 20803488.
There is no reason why these approaches can't be used in a benchtop NMR.
  • asked a question related to Asymmetric Synthesis
Question
4 answers
Folks involved in the synthesis of organic compounds or anyone with organic lab setup expertise:
Would you recommend buying a chiller over a submersible water pump (a cheaper option-can buy a few for the same price for rotovap and distillation setup)
  1. If we purchase a chiller, can we connect multiple units (again rotovap and distillation units) at the same time?
Thank you.
Relevant answer
Answer
I would like to recommend you chiller option (green, energy saver and more efficient) instead of the submersible water pump.
  • asked a question related to Asymmetric Synthesis
Question
20 answers
I would like to make some modifications of my flavonoids for the sake to enhance the pharmaological activity.
Is it possible and practical ? And what kind of reagents will be more convenient?
Any suggestions or articles will be more valuable.
Thank you,
Relevant answer
Answer
Dear Ayoub Najem many thanks for sharing this very interesting technical question with the RG community. Flavonoids normally have several –OH groups at different positions, so that a variety of fluorinated derivatives are possible. There are some literature references available in which the authors describe the use of elemental fluorine (diluted with nitrogen) as fluorinating agent. However, most organic chemistry laboratories are not properly equipped for woorking with elemental fluorine.
An alternative synthetic route involves the synthesis of fluorinated flavonoids starting from fluorinated benzene derivatives. For more information, please have a look at the following potentially useful articles:
Synthesis and anti-rhinovirus properties of fluoro-substituted flavonoids
and
Separation of Quercetin’s Biological Activity from Its Oxidative Property through Bioisosteric Replacement of the Catecholic Hydroxyl Groups with Fluorine Atoms
The first article is freely available as public full text from the internet (please see the attached pdf file). The second article has not been posted as public full text on RG. However, one of the authors has an RG pprofile (https://www.researchgate.net/profile/Suh-Cho-2). Thus you can easily contact him directly via RG and request the full text.
I also came across a Master thesis which could provide useful information about this topic:
Synthesis of Fluoroflavones as Potential Neuroprotective Agents
(also attached)
Good luck with your research and best wishes, Frank Edelmann
P.S. Please also share this question with the "flavonoid guru" Yasser Fakri Mustafa
  • asked a question related to Asymmetric Synthesis
Question
4 answers
Hi every body
would you please help me how is mechanism of Oxidation Alcohol to Carboxylic acid using CuCl and t-BuooH?
I found this reaction in this paper:
Relevant answer
Answer
Mohammadi
Please, see
---Y. Zhu, H. Yan, L. Lu, D. Liu, G. Rong, J. Mao, J. Org. Chem., 2013, 78, 9898-9905
  • asked a question related to Asymmetric Synthesis
Question
6 answers
What will be the effect on specific rotation, if we measure the values in two different solvents?
Relevant answer
Answer
Effects of solvents on both optical absorption and optical rotation are well known and documented since long. Even the classic book, Optical Rotary Power by T. Martin Lowry, 1964 lists several cases where the optical rotation changes in magnitude as well as sign with solvent change. Regarding optical absorption: there are several publications reporting shift in position of the peak, as well as change in the strength of absorption with solvent change.
The comment made about measuring blank seems to be off the mark: Yes, optical rotation of the sample has to be measured with respect to the blank as a rule - BUT - in all cases solvents are non chiral, and the optical rotation of the blank solvent filled cell is always close to zero. The blank measurement is more to correct for the spurious rotation introduced by the sample cell and its windows, and not for solvent rotation.
That is the reason why the protocol is to measure the solvent blank and sample in the same sample cell, oriented in the same way on the sample trough. Some polarimeters and the cells used with them have arrangements to ensure that the cell is always positioned in exactly the same way.
If the solvent blank rotation comes out to be significantly different from zero, it either means the solvent has some chiral impurities in it and should be thrown out or the cell windows are defective and should be changed.
  • asked a question related to Asymmetric Synthesis
Question
4 answers
CAS:187037-23-6, have checked with Santa Cruz, SIgma and Fisher.
Relevant answer
Answer
Hi,
You may buy it at Alfa Chemistry.
  • asked a question related to Asymmetric Synthesis
Question
4 answers
I need the experimental method for the synthesis of 3-phenylpropynenitrile.
Relevant answer
Answer
Please see attached file. Hope it helps. Good luck
  • asked a question related to Asymmetric Synthesis
Question
4 answers
If such a protein has in fact been synthesized, has it been shown to be crystallizable and amenable to x-ray crystallographic 3D structure determination?
Relevant answer
Answer
I am not sure about proteins composed of D-amino acids only, but recently it was shown successful for the racemic mixture of L and D- synthesised proteins. See the following paper: 
"A functional role of Rv1738 in Mycobacterium tuberculosis persistence suggested by racemic protein crystallography".
  • asked a question related to Asymmetric Synthesis
Question
3 answers
 actually m working on asymmetric synthesis, nitro olefine as substrate and diphenylphosphonate as a nucleophile, after getting final product isnt resolving in hplc.
Relevant answer
Answer
In general there many ways for separation of chiral compounds in HPLC such as derivatization, chiral mobile phase additives and the use of chiral column, can you be more specific of which procedure you have the possibility to follow ??
  • asked a question related to Asymmetric Synthesis
Question
4 answers
Provide me some stabilizer if some body knows, with some relative reference
which will be greatful
Relevant answer
Answer
Stabilize with respect to what?  When conditions are you envisioning?
  • asked a question related to Asymmetric Synthesis
Question
11 answers
If somebody has reported first asymmetric synthesis then can some another person report first enantioselective synthesis?
Relevant answer
Answer
Hi
According to IUPAC
  • asymmetric synthesis
  • A traditional term used for stereoselective synthesis of chiral compounds
  • stereoselective synthesis
  • A chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereoisomeric) products in unequal amounts. Traditionally called asymmetric synthesis.
I think, In recent years,  scientists are more precise;  "enantioselective synthesis" to designate a major enantiomer product of a reaction) "diastereoselctive synthesis" to designate a major diastereomer product of a reaction).
Dr Mustapha is right but I think we say JUST for diastereoselective synthesis because enantioselective synthesis is the purest form. 
please see the link below 
  • asked a question related to Asymmetric Synthesis
Question
3 answers
Enzymatic or chemoselective resolution of corey lactone benzoate. Any literature references are most welcome.
Relevant answer
Answer
Babu,
Please, find some literature
Good luck
  • asked a question related to Asymmetric Synthesis
Question
15 answers
I tried to synthesis the aforementioned compound by reacting 2,4-dihydroxybenzaldehyde and ethyl acetoacetate in the present of piperidine as catalyst. According to the method that I'm using, after being left overnight, yellow solid should be forming. However I did not obtained any solid the next day. Can somebody share another method to synthesis this compound?
Thank you in advance. 
Relevant answer
Answer
The knoevenagel condensation you are using is one of the best ways of obtaining your product. Just because you haven't observed a solid yet, it doesn't mean the reaction hasn't worked. The transesterification may not have gone to completion; try heating it up and cooling down again.
Repeat the reaction, use toluene or benzene as a solvent at reflux and a dean stark apparatus to drive off water and ethanol formed in the reaction. Monitor by TLC.
  • asked a question related to Asymmetric Synthesis
Question
2 answers
Chiral Synthesis
Relevant answer
Answer
Most of the chiral diamines are biologically active especially in HIV protease inhibitors, anti-inflammatory and cytotoxic. Also they may act as better resolving agents.
  • asked a question related to Asymmetric Synthesis
Question
4 answers
Please give details with below points......
1) Does the nucleus spin faster?
2) Does the precessional frequency of the nucleus increase or decrease?
3) Does the angle of precession " flip " so that the magnetic moment of the nucleus opposes the applied field or with the the applied?
4) Any other?
Relevant answer
Answer
3 - magnetic moment of the nucleus /previously parallel with the outer magnetic field /- it pays for the nucleus from a small excessive population of nuclei with the lower energy, otherwise the +1/2 and - 1/2 spin populations are almost equal and almost well balanced/ flips due to absorbed quantum of radiofrequency radiation against direction of the applied outer magnetic field to achieve equality of both populations.
  • asked a question related to Asymmetric Synthesis
Question
1 answer
I also have an amino functional group in the molecule of interest.
Relevant answer
Answer
Thank you...
  • asked a question related to Asymmetric Synthesis
Question
3 answers
We are facing 1,5-hexadiene as a major impurity.
Relevant answer
Answer
It is Grignard reaction & you can react allyl chloride with Mg metal in dry THF by standard procedure
  • asked a question related to Asymmetric Synthesis
Question
1 answer
I have tried with BF3 Etherate (Freshly Distilled) and MOMCl protection method but of no use yield was so less
Relevant answer
Answer
You may try Thallium(III) nitrate.
  • asked a question related to Asymmetric Synthesis
Question
5 answers
I am trying to synthesize N-Protected Beta-Amino Ketones via mannich reaction. I tried to synthesize it using many reagents such as Sulfamic acid, Molecular Iodine, l-Prolin, PTSA etc., but I could not succeed. The products with CBZ protected Beta-Amino Ketone have been reported with some of the catalysts I mentioned above. The only thing I am changing is tert-Butyl carbamate instead of Benzyl carbamate.
The reaction condition I use are:
1 mmol benzaldehyde, 1 mmol acetophenone, 1 mmol tert-Butyl carbamate and 10 mol% catalyst and stirring them at RT. I tried these reactions for 48 hours but I could not get the desired products. What should I do to complete the reaction? Am I going wrong with the reaction?
Please help, the scheme is attached here.
Relevant answer
Answer
Catalyze your Mannich reaction by action of CeCl3 . 7H2O dopped by NaI – use this system directly or support this on silica gel or use Ce(III) supported on a weak acid cation-exchanger of a polyacrylate macroporous kind, ideally (preparations and synthetic application of such supported catalysts are described in patent CZ 2011/0799 (A3), Pazdera P. et al.).
  • asked a question related to Asymmetric Synthesis
Question
4 answers
Whereas in crystallography, as for example in the case of symmetry classification of atomic crystal groups there are only 234 possible classes of symmetry space-groups (that are precisely defined mathematically in terms of symmetry operations such as reflections and rotations, etc.), in material science, nanoscience (e.g. molecular crystals and quasi-crystals) things may appear not be as neatly and completely defined even when the local symmetries are precise and are well-defined because mathematical groups become then insufficient to classify the latter structures that possess broken symmetry, or only local symmetries thereof. A certain type of asymmetry or noncommutativity is fundamental in non-Abelian mathematics, such as Non-Abelian Algebraic Topology, Anabelian Geometry and Noncommutative Geometry.
Relevant answer
Answer
Hi Ion: You must be talking about some high crystallography! I know only 230 space from my International Tables! You can of course increase them largely if you take into acount time reveral symmetry (magnetic black and white space groups)!! I was just joking of course!
You have raised a very important point. The reductionists think that if you go down and down and discover the fundamental laws of nature they you can explain everything. This is of course a fool's philosophy. The physical laws are highly symmetric. But the world we see is not symmetric. The symmetry breaking is the most important ingredient to explain our macroscopic world. A large collection of particle (N-body problem) often beak symmetries of the fundamental physical laws and lo the emergent phenomena: materials science and even biology.
I don't have any more now. I shall come back to you later and discuss further with you about symmetry breaking and emergent phenomena. More is different as P>W> Anderson says!
  • asked a question related to Asymmetric Synthesis
Question
4 answers
I have tried to synthesize samarium diiodide with samarium metal and iodine in THF, but I don´t get the dark blue solution, and my reduction reaction does not work. Does anyone have experience with this reagent?
Relevant answer
Answer
Wellcome to the club! I did this prep 18 years ago ....! The main problem is: you need to be 110% super dry. Fresh distilled THF, under argon then all additions under Argon. It can take up to 48h to get the dark blue solution